Contents

A&A 451, 157-175 (2006)
DOI: 10.1051/0004-6361:20053396

The nature of ultraviolet spectra of AG Pegasi and other symbiotic stars: locations, origins, and excitation mechanisms of emission lines[*]

M. Eriksson1,2 - S. Johansson2 - G. M. Wahlgren2


1 - University College of Kalmar, 391 82 Kalmar, Sweden
2 - Atomic Astrophysics, Lund Observatory, Lund University, Box 43, 221 00 Lund, Sweden

Received 10 May 2005 / Accepted 4 December 2005

Abstract
A detailed study of ultraviolet spectra of the symbiotic star AG Peg has been undertaken to derive the atomic excitation mechanisms and origin of formation for the lines common in symbiotic systems. More than 600 emission lines are observed in spectra from ${\it IUE}$, ${\it HST}$ and ${\it FUSE}$ of which 585 are identified. Population mechanisms and origin of formation are given for a majority of those lines. Based on the understanding of the AG Peg spectra ${\it IUE}$ data of 19 additional symbiotic stars are investigated and differences and similarities of their spectra are discussed. Fe II fluorescence lines pumped by strong emission lines between 1000 and 2000 Å are observed in 13 of these systems. Some of the symbiotic systems belonging to the subclass symbiotic novae have more than 100 Fe II fluorescence lines in the ultraviolet wavelength region. Forbidden lines are detected for 13 of the stars, mostly from highly-ionized spectra such as Ar V, Ne V and Mg V. Further, [Mg VI] and [Mg VII] lines are observed in a symbiotic star (AG Dra) for the first time. Five of the symbiotic stars have broad white-dwarf wind profiles ( ${\it FWHM} > 400$ km s-1) for a few lines in their spectra. The stars with no such broad lines can be divided into two similarly sized groups, one where all lines have FWHM less than 70 km s-1 and the other where one, a few or all of the broad ( ${\it FWHM} > 400$ km s-1) lines of AG Peg have an enhanced broad wing (110-140 km s-1).

Key words: atomic processes - line: formation - stars: binaries: symbiotic - ultraviolet: stars

1 Introduction

From numerous recordings with the ${\it IUE}$ satellite during 1978 to 1995 symbiotic stars are today known to be interacting binaries consisting of a white dwarf and a red giant with orbital periods of typically a few years. Symbiotic stars have composite spectra, an M-star continuum dominating at red and infrared wavelengths, a nebula continuum at ultraviolet and optical wavelengths, a rising continuum toward the far ultraviolet from the presence of a hot component and numerous strong emission lines throughout the spectrum indicating large plasma regions within the systems.

AG Peg is a symbiotic system consisting of a white dwarf and a red giant orbiting each other with a period of $812.3\pm6.3$ days (Kenyon et al. 1993). The luminosity of the white dwarf decreased by a factor of $\sim$4 during 1984-1997 (Kenyon et al. 2001). This decline can be understood as a decrease of its radius by a factor of $\sim$2 under constant temperature (Altamore & Cassatella 1997; Mürset & Nussbaumer 1994) or as an increase in the temperature of the white dwarf Schmutz 1996, which would imply a even larger decrease of its radius.

Between the two stars there is a region where the fast wind ( $v=~\sim\!900$ km s-1) (Nussbaumer et al. 1995) from the white dwarf collides with the slow wind ( $v=~\sim\!60$ km s-1) (Eriksson et al. 2004) from the red giant (Mürset et al. 1995). More recent and detailed ideas are discussed with respect to the wind structure concerning shock fronts from the wind collision region (Contini 2003) and the possibility of bipolar outflow (Yoo et al. 2002).

AG Peg belongs to a small subclass of symbiotic stars called symbiotic novae that have undergone nova events when the luminosity has increased by three to four magnitudes. Ultraviolet region line lists are available for two symbiotic novae, RR Tel (Penston et al. 1983) and V1016 Cyg (Nussbaumer & Schild 1981). Both of these systems have spectra dominated by allowed transitions from one to three times ionized elements, but also forbidden lines from more highly ionized elements have an impact on the spectrum. V1016 Cyg erupted in 1964 and RR Tel in 1944, while AG Peg erupted at least 150 years ago. An interesting open question is whether the decline of the UV flux in AG Peg during the 1980s is a natural evolutionary stage of symbiotic novae and whether, subsequently, RR Tel and V1016 Cyg will undergo a similar spectrum evolution in the future. A time analysis of the AG Peg spectrum can therefore give insights into what happens at the end of nova eruptions in symbiotic stars.

During the last 25 years the emission lines in AG Peg have been used for various diagnostics to measure parameters such as electron density (Keyes & Plavec 1980; Penston & Allen 1985) and temperature (Kenyon & Webbink 1984; Altamore & Cassatella 1997). By careful analysis of the spectra it is possible to categorize the emission lines in terms of population processes and line profiles. It is important to understand the origins of the emission lines as well as the processes that populate the corresponding upper levels when using them in any analysis. Here we explain the appearance of most of the emission lines formed at UV wavelengths in AG Peg. The main goal is to obtain an enhanced understanding of the emission lines, which would be helpful for anyone who wants to use emission lines as a diagnostic tool for symbiotic stars or related novae-like environments. Furthermore, the spectral investigation gives insight into how the UV spectum has evolved during the period 1978-1995.

Symbiotic stars are categorized in terms of stellar (S) and dusty (D) types based on their appearence at IR wavelengths (Allen 1982). The S-types have typical orbital periods of a few years and the cooler component consists of a solar-mass star on the red giant branch, while the D-types have orbital periods mostly in excess of 20 years and the cool component in those systems is typically a Mira. The small subset of D' type symbiotic stars has a cool star of spectral type G or K rather than M (Belczynski et al. 2000). The hot components are dominantly white dwarfs in both the S and D type systems. However, a few exceptions have the hot component as an accreation disk around a main sequence star (Kenyon & Garcia 1986).

Beyond the shared basic properties defining the group, the characteristics of symbiotic stars differ significantly. Besides the nova-like outbursts exhibited by the symbiotic novae, other phenomena observed in symbiotic stars are white-dwarf winds (Nussbaumer et al. 1995), recurrent-novae eruptions (Belczynski & Mikalojewska 1998), jets (Burgarella et al. 1992) and wind collision regions (Mürset et al. 1997).

By applying the understanding of the AG Peg spectrum at UV wavelengths to a set of 19 symbiotic stars we aim to detect differences and similarities among them. A detailed study of the lines showing broad white-dwarf wind lines in AG Peg is done to see how common such winds are in symbiotic systems. Fe II lines caused by photo-exitation by accidental resonance (PAR) are investigated to see whether this phenomenon is unique to a few symbiotic stars (Eriksson et al. 2003; Hartman & Johansson 2000) or more common among such systems. Also, forbidden lines of highly-ionized ions are analyzed to compare the ionization degree of low-density regions in symbiotic stars.

 

 
Table 1: Spectra used for AG Peg.
Instrument Coverage (Å) Spectum identification
IUE (LWR) 1900-3350 02591, 06389, 07504
    09672, 09310, 10579
IUE (LWP) 1900-3350 09698, 16684, 19235
    21635, 24149, 24285
    25565, 25995, 28122
    30936
IUE (SWP) 1150-1980 02326, 02334, 06335
    06809, 08760, 10454
    13957, 15651, 29862
    29863, 37420, 37477
    40149, 43006, 43007
    46149, 47715, 50707
    54749, 55055
HST (GHRS) 1222-1258 z27e0206t
  1354-1389 z27e0207n
  1383-1418 z27e0208t
  1468-1503 z27e0209t
  1532-1567 z27e020at
  1623-1657 z27e020bn
  1696-1737 z27e020dt
FUSE (LWRS) 920-1190 Q1110101
FUSE (MDRS) 920-1190 Q1110103



  \begin{figure}
\par\includegraphics[angle=-90,width=8cm,clip]{3396fi1.eps}
\end{figure} Figure 1: The dots represent the noise level for each of the different orders in the longest exposed IUE spectra, LWP25995 and SWP47715. The lines represent the noise level in the ${\it HST}$ and ${\it FUSE}$ spectra used in this work. The y-axis gives the value of the logarithm of the noise level measured in erg cm-2 s-1 Å-1. The noise level is defined as twice the standard deviation of the pixel intensity from the mean intensity, measured in wavelength regions not affected by spectral lines.

2 Data

The present study utilizes ultraviolet spectral data obtained from three different satellite observatories, spanning over nearly 25 years. The data were extracted from the Multimission Archive at STScI (MAST) in reduced format and are listed in Table 1. The extensive temporal coverage (1978-1995) of the International Ultraviolet Explorer IUE data for AG Peg allows us to follow spectrum developments during these years. The same data were exploited by Eriksson et al. (2004) to study wind affected line profiles for this star. Figure 1 prestents the noise levels for each spectral order for the longest exposures of the IUE high resolution observations. The figure thus provides a guide to the weakest detectable features and possible explanation for the relative strength of observed features. The resolution of ${\it IUE}$ spectra depends on several parameters, such as the dispersion angle, the reduction routine used and the wavelength being considered. No instrumental profile is deconvolved from the FWHM given in tables in this paper. Imhoff 1984 measured widths of platinum lines, with the FWHM being between 16 and 30 km s-1. Therefore, the widths of lines narrower than 40 km s-1 in our tables should be treated with caution.

The data recorded by the Goddard High Resolution Spectrograph (GHRS) onboard the Hubble Space Telescope (HST) during 1994 overlap in wavelength with the IUE data but were recorded at a later epoch and for only limited wavelength intervals. The greater sensitivity of the GHRS detectors makes it possible to measure intensities to a greater accuracy than can be done from the IUE spectra.

Two spectra of AG Peg have been recorded by the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite, one in July 2001 and one in June 2003. The inclusion of FUSE spectra in our analysis increases the wavelength range for the detection of emission lines. However, since those spectra were obtained several years after the IUE and HST data we must be careful when incorporating these data sets into the analysis. The spectrum of AG Peg underwent obvious changes during the lifetime of the IUE (Eriksson et al. 2004) and we might expect that its development would continue in the sense that certain spectral lines would increase or decrease in intensity and width. Without contemporaneous observations in other wavelength regions, emission line intensities from the FUSE data cannot be rigorously correlated with the line intensities at longer wavelengths.

For the symbiotic stars other than AG Peg presented in this analysis only ${\it IUE}$ data are used. Since some of the Fe II lines as well as some of the forbidden lines are quite weak, one SWP and one LWP spectrum, observed with large aperture and with long exposure time, were selected for each system. The emission lines associated with the white-dwarf wind in AG Peg were easily saturated in the ${\it IUE}$ spectrum, which is why an extra SWP spectrum was retrieved from the MAST archive for some of the symbiotic systems. Table 2 lists the data used for the selected objects.


   
Table 2: IUE spectra used for the selected symbiotic stars.
Object LWP/LWRa SWPa SWPb
Z And LWP06225 26177 26938
EG And LWP25855 56021 46879
R Aqr LWP21998 31102 40265
T CrB LWP01536 28490  
BF Cyg LWP15253 35843 58386
CH Cyg LWP08631 28011  
CI Cyg LWR10427 18602 50760
AG Dra LWP24400 15656 55373
RW Hya LWR10227 13601  
SY Mus LWR10829 14236 16383
AX Per LWP19332 21443 06807
RX Pup LWR10831 31285 16597
HM Sge LWP12921 40081  
RR Tel LWR16187 20246 18371
KX Tra LWP17871 38742  
PU Vul LWP26780 37190 49265
V1016 Cyg LWP04961 29830 24657
V1329 Cyg LWP13121 24663 05615
HBV475 LWP08277 30853  
a Spectrum with long exposure times used to detect
  weak Fe II fluorescence lines and forbidden lines.
b Spectrum with short exposure times used when allowed
  lines are saturated in longer exposed spectra.

3 Excitation and origin of AG Peg emission lines

The spectral lines can be divided into different categories depending upon their widths and profiles. However, lines that look similar in one spectrum can show a different appearance in later spectra. This means that the time history of a spectral line is also important. Some narrow lines are selectively populated by radiative line excitation and they are classified as fluorescence lines, whereas others originate from excited levels populated by collisions or recombination. We have categorized the spectral lines by their overall appearance in the following way:

1.
Broad emission lines ( ${\it FWHM} > 500$ km s-1) in spectra until 1981 that later evolve into narrower ( ${\it FWHM }< 80$ km s-1) emission lines.
2.
Emission lines caused by fluorescence.
3.
Narrow emission lines from levels excited by collisions.
4.
Narrow emission lines from levels populated by recombination.
5.
Narrow emission lines from levels with an uncertain population mechanism.
6.
Interstellar absorption lines
7.
Stellar absorption lines.
The lines showing a broad structure originate from ions of higher ionization stages, and they are partially or completely formed in the wind of the white dwarf before 1980 (Eriksson et al. 2004). During 1980-1985 the broad contribution from the white-dwarf wind to these lines vanished as a result of the reduced bolometric luminosity (a factor of 2-3) of the white dwarf. Narrow "nebular'' lines replaced these broad wind lines in later spectra. Unfortunately, no ${\it IUE}$ spectra of AG Peg were recorded during the years 1982 to 1985, when most of the line profiles must have undergone a rapid change. The narrow lines are most probably formed at further distance from the white dwarf, like in the extended parts of the red giant, such as its wind or upper atmosphere, or in the surrounding nebula. These lines involve mostly permitted lines and intercombination lines, but there are also a few forbidden lines originating from metastable states with lifetimes on the order of seconds. Most of the absorption lines are believed to be formed in the outer parts of the surrounding nebula (Penston & Allen 1985). In Table 3 we present for each element the number of identified lines observed in the UV spectrum of AG Peg.


   
Table 3: The distribution of emission lines for AG Peg, according to population processes.
Spec. Processa Tot   Spec. Processa Tot
  fl. rec. col. unk       fl. rec. col. unk  
H I   1     1   [Ne V]     3   3
He I   8     8   Mg II     2 7 9
He II   14     14   Mg IV   7     7
C II     5 3 8   [Mg V]     3   3
C III   8   3 11   Al II]     1   1
C III]     2   2   Al III     2   2
C IV     2   2   Si I       5 5
N I 1     4 5   Si II     3 5 8
N I]     4   4   Si II]     2   2
N III   5   4 9   Si III       4 4
N III]     5   5   Si III]     1   1
N IV   1     1   Si IV     2 5 7
N IV]     2   2   P II     3 1 4
N V     2   2   P II]     1   1
O I     2   2   P III     2   2
O I]       2 2   P IV       1 1
O III 16 6     22   P IV]     1   1
O III] 1 1 3 2 7   S I 1   5   6
[O III]     1   1   S I]     1   1
O IV   3   2 5   S II]     1   1
O IV]   5     5   S IV]     5   5
O V   3   1 4   S V       1 1
O V]       1 1   S V]       1 1
O VI     2   2   [Ar V]     1   1
Ne III   8     8   Fe II* 226 3 85 32 346
Ne III]   2     2   Fe III 3     11 14
[Ne III]     1   1   Fe V   4     4
[Ne IV]     4   4   [Fe VI]     2   2
Ne V]     2   2   Co II* 5     6 11
$\textstyle \parbox{12cm}{
$^{*}$\space Spin-forbidden transitions are also incl...
...\space fl = fluorescence; rec = recombination; col = collision; unk = unknown.}$



   
Table 4: The broad emission lines in AG Peg spectra.
      Before 1986     After 1986
Line IPa   FWHMb Intc     FWHMb Intc
He II $\lambda $3203 24.6   800 394A     40 550B
He II $\lambda $2733     770 235A     61 326B
He II $\lambda $2511     790 215A     40 243B
He II $\lambda $2385     800 207A     48 300C
He II $\lambda $2307     740 143A     40 235C
He II $\lambda $1640     770 7370D     66 22 040E
C IV $\lambda $1550 47.9   tcp tcp     45 24 420E
C IV $\lambda $1548     tcp tcp     37 44 470E
N IV $\lambda $1718 47.5   680 1443D     <145 214F
N IV] $\lambda $1486     tcp tcp     32 14 200E
N V $\lambda $1242 77.5   800 4168D     56 12 570E
N V $\lambda $1238     430 3529D     70 19 560E
O V $\lambda $2781 77.4   820 54A     38 29C
O V $\lambda $1371     860 424G     <83 473F
Ne III $\lambda $2678 41.0   480 128A     37 28C
Si IV $\lambda $1402 33.5   tcp tcp     36 2439E
Si IV $\lambda $1393     tcp tcp     37 3796E
S V $\lambda $1502 45.1   820 358G        
S V] $\lambda $1199     770 480G     40 1066C
unid $\lambda $1266     550 858G        
unid $\lambda $1260     700 1556G        
unid $\lambda $1253     790 1469G        
a The ionization potential in eV of the next lower ion. b Given in km s-1. c Peak intensity in units of 10-14 erg cm-2 s-1 Å-1. The indices on the measured intensities stand for: A As measured in LWR05596, B LWP28122, C LWP25995, D SWP02326, E SWP55055, F SWP47715, G SWP02334. tcp = Two component profile as the spectral line has a narrow emission component superimposed on the broad white dwarf wind profile.

3.1 Broad wind lines

In IUE spectra recorded before 1986 there are 22 emission lines with a FWHM larger than 600 km s-1 (Table 4). These lines originate from abundant elements in higher ionization stages than for the narrow lines, and they are presumably formed in the hot white-dwarf wind. An analysis of some of these lines has yielded that the terminal velocity of the white-dwarf wind is $\sim$900 km s-1 (Vogel & Nussbaumer 1994). A few of the lines are ground-state transitions (resonance lines) and show P Cygni structure while others are LS-allowed transitions having an excited lower level. In a few cases the transitions are spin-forbidden (intercombination lines). After 1986, when the broad wind lines were replaced by narrow emission (Fig. 2), it is notable that the six lines with highest peak intensity in the ${\it IUE}$ spectra (He II $\lambda $1640, C IV  $\lambda\lambda$1548, 1550, N IV] $\lambda $1486, N V $\lambda\lambda$1238, 1242) had broad line profiles in earlier spectra.

He+ has a low ionization energy compared to the other emitting ions detected in the white-dwarf wind, which is why the He II lines can be considered as recombination lines. The He II lines with wavelengths in the range of ${\it IUE}$ are Balmer $\alpha $, Balmer $\beta$, and the whole Paschen series except Pa$\alpha $. He II Balmer $\beta$ is close in wavelength to H Ly$\alpha $ and therefore totally absorbed. The He II lines detected in ${\it IUE}$ spectra of AG Peg are He II Balmer $\alpha $ and 13 consecutive Pashen lines starting with Pa$\beta$ and reaching upper levels with quantum numbers n=5-17. Only the second to the sixth lines can be detected from the noise before 1986 when the lines were broad.

  \begin{figure}
\par\includegraphics[angle=90,width=7.5cm,clip]{3396fi2a.ps}\hspace*{2mm}
\includegraphics[angle=90,width=7.5cm,clip]{3396fi2b.ps}
\end{figure} Figure 2: The development of He II Balmer $\alpha $. The spectrum to the left (SWP02326) was recorded in 1978 and the spectrum to the right (SWP40148) was recorded in 1990. The large change in profile width is related to the change in origin for He II emission between those dates. In 1978 most of the He II emission originated from the white-dwarf wind while in 1990 the emission instead came from the heated part of the extended red-giant atmosphere.

For a few of the white-dwarf lines (C IV $\lambda\lambda$1548, 1558, N IV]1486, Si IV $\lambda $1402, Si IV $\lambda $1393) the development into narrow "nebular'' lines had already started in 1978, and the structure in the line profile, as shown in Fig. 3, is caused by the narrow line superimposed on the broad line. That the contribution of narrow emission lines occurred earlier for the ions of lower ionisation potential gives an idea into why the emission lines changed origin. As the white dwarf emerged at the end of the nova-like outburst the wind became less dense and more transparent for UV photons. The line intensities from the white-dwarf wind would then decrease at the same time that the material in the extended part of the red-giant atmosphere facing the white dwarf would be subjected to more of the white-dwarf UV radiation. The heated part of the red giant atmosphere became hotter and more ionised, resulting in the strong, narrow-emission lines. In recent ${\it FUSE}$ observations of AG Peg it is clear that the O VI resonance doublet still has contributions from the white-dwarf wind (Fig. 8). Since the ionisation energy of O VI is 114 eV its presence would be expected with a temperature increase in the white-dwarf wind, contrary to what is given by Zanstra determinations (Altamore & Cassatella 1997).

The O III Bowen lines were also broader than the nebular lines in early ${\it IUE}$ spectra. Like the white-dwarf lines discussed earlier the O III Bowen lines also evolved into narrower lines during the 1980s. The reason that they are not included in Table 4 is that they have less than half of the FWHM of the other broad line profiles and are formed in a different way (fluorescence). The Bowen lines are discussed in Sect. 3.3.


  \begin{figure}
\par\includegraphics[angle=90,width=7cm,clip]{3396fi3a.ps}\hspace*{2mm}
\includegraphics[angle=90,width=7cm,clip]{3396fi3b.ps}
\end{figure} Figure 3: The IUE spectrum (SWP02334) of AG Peg, recorded in 1978, illustrates the difference in the profiles between lines from ions of ionisation energy near 40 eV and those of higher ionisation energy (around 70 eV). The N IV] $\lambda $1486 had a contribution from a "nebular line'' already in 1978 while all flux in the N V resonance doublet came from the white-dwarf wind.

3.2 The "nebular'' lines

A majority of the emission lines observed in IUE spectra of AG Peg have a FWHM between 10 and 50 km s-1 and have had the same line profile although changed in intensity between 1978 and 1995. There is a wide range in ionisation energy for the narrow lines, from singly-ionised elements to more highly-ionised species such as Mg V, S IV and Fe V. Most of the emission lines correspond to LS-allowed transitions or intercombination lines but there are also a few parity-forbidden lines such as [Mg V] $\lambda $2928.

3.2.1 Narrow fluorescence lines

The process of photo-excitation by accidental resonance (PAR) can account for as many as 218 of the 585 identified lines in ${\it IUE}$ spectra of AG Peg. The Fe II levels y4H11/2 and w2D3/2 are known to be pumped by C IV $\lambda $1548 in at least eight symbiotic systems (Johansson 1983; Eriksson et al. 2001). The levels (5D)5p 6F9/2 and (3F)4p 4G9/2 are known to be pumped by H Ly$\alpha $ in the symbiotic star RR Tel (Johansson & Jordan 1984; Hartman & Johansson 2000) and they are involved in laser action in gas condensations of $\eta$ Car (Johansson & Letokhov 2004). In an analysis of AG Peg (Eriksson et al. 2003) 29 Fe II levels were shown to be populated by the PAR mechanism, and in the present work 11 newly identified pumped channels lead to a total of 40 presumably pumped Fe II levels, of which 22 are confirmed by three or more fluorescence lines (Table 5).


   
Table 5: Pumped Fe II channels confirmed by 3 or more fluorescence lines.
Pumping Line Fe II channel $\delta$ $\lambda^{a}$ (Å) No.b
Si III] $\lambda $1892.03 a4P3/2-x4F5/2 0.15 6
Si III] $\lambda $1892.03 a4D7/2-z4G9/2 0.05 14
N IV $\lambda $1718.55 a6D3/2-z4G5/2 -0.45 6
O III] $\lambda $1666.15 a6D7/2-y4P5/2 0.03 4
O III] $\lambda $1660.81 a4F9/2-z2G9/2 0.03 5
He II $\lambda $1640.07 a4F3/2-y4G5/2 0.08 4
C IV $\lambda $1548.19 a4F9/2-y4H11/2 0.01 13
C IV $\lambda $1548.19 a4F7/2-y2D5/2 0.51 7
C IV $\lambda $1548.19 a4P1/2-w2D3/2 0.22 13
N IV] $\lambda $1486.50 a4G5/2-u4F3/2 -0.03 7
O IV] $\lambda $1401.16 a6D5/2-(3D)4p 4P3/2 -0.12 4
N V $\lambda $1242.78 a4F5/2-v2G7/2 -0.04 3
N V $\lambda $1238.80 a4P5/2-(4P)4s4p 4P5/2 -0.22 5
H I $\lambda $1215.67 a4D5/2-(b3P)4p 4S3/2 0.31 4
H I $\lambda $1215.67 a4D5/2-(5D)5p 4D5/2 0.18 6
H I $\lambda $1215.67 a4D1/2-(5D)5p 4D3/2 0.85 5
He II $\lambda $1084.94 a6D9/2-x4H7/2 0.96 4
He II $\lambda $1084.94 a6D9/2-x4H9/2 0.64 3
He II $\lambda $1084.94 a6D9/2-x4H11/2 0.05 3
He II $\lambda $1084.94 a6D9/2-u2G9/2 -0.01 3
He II $\lambda $1025.27 a4D1/2-(4F)4s4p 6F3/2 -0.17 5
He II $\lambda $933.45 a4F5/2-(3H)5p 4G7/2 -0.07 6
a $\lambda_{\rm lab}$(pumped Fe II channel) - $\lambda_{\rm lab}$(pumping line).
b Number of observed Fe II fluorescence lines from the pumped level.

Most of the spectral lines that pump (selectively excite) Fe II are formed in the white-dwarf wind. Since the profiles of those lines change as their origin evolves from being dominated by the white-dwarf wind to the heated part of the red-giant atmosphere (or wind) the emission from the pumped Fe II levels also changes after 1986. Fe II channels that are separated by more than 40 km s- 1 from their pumping line cannot be pumped by the narrow emission lines and therefore those lines disappeared after 1986 (Fig. 4). However, the Fe II fluorescence lines excited in channels that are close in wavelength to their pumping lines can be pumped by the narrow "nebular'' emission lines and they do appear in the spectrum throughout the lifetime of IUE. There are four lines from highly- ionised elements (Si III] $\lambda $1892, O III]  $\lambda\lambda$1660, 1666 and O IV] $\lambda $1401), which are not white-dwarf wind lines but still responsible for PAR processes in Fe II. These lines have in common that they are narrower than the other pumping lines, even compared to the FWHM after 1986, and that they, along with the corresponding fluorescence lines, did not change during the years 1978-1995.

In AG Peg H Ly$\alpha $ activates numerous Fe II channels resulting in fluorescence lines from both primary and secondary decays of the pumped levels. Lines from the (5D)5s levels (i.e. the e6D and e4D terms) are seen in the AG Peg spectrum. Those lines are also seen in RR Tel, where they are explained as secondary decay from H Ly$\alpha $ pumped (5D)5p levels (Hartman & Johansson 2000), and we conclude that the same explanation is valid for AG Peg. A consequence of the density decrease in the white-dwarf wind is that it becomes less dominant (less extended in the binary system) as well as less opaque so that the H II region can grow and more H Ly$\alpha $ radiation can reach the Fe+ ions. This leads to an increase of the intensity of the H Ly$\alpha $ pumped Fe II fluorescence lines (Fig. 5). It is interesting to note that the velocity shift is the same for the Fe II fluorescence lines but differs from the velocity shift of the lines from collisionally excited Fe II levels.


  \begin{figure}
\par\includegraphics[angle=270,width=8cm,clip]{3396fi4.eps}
\end{figure} Figure 4: The total intensity of all Fe II lines from the upper level y2D5/2, which is pumped by the C IV $\lambda $1548.187 line through the channel a4F7/2-y2D5/2 at 1548.697 Å. When the broad foot of the C IV resonance lines vanished the activity in this channel stopped.


  \begin{figure}
\par\includegraphics[angle=270,width=8cm,clip]{3396fi5.eps}
\end{figure} Figure 5: The strength of the $\lambda $2508.34 Fe II line representing the channel a4D7/2-(b3F) 4p 4G9/2 pumped by H Ly$\alpha $. As the temperature increased the H II region around the white dwarf became larger, which allowed more H Ly$\alpha $ to reach the Fe II regions.

We observe lines from Fe II levels that are not selectively photo-excited by strong lines. The population of these levels can in general be explained by collisional or recombination excitation (see later sections). However, we also observe emission lines from 21 Fe II levels of medium excitation energy ( ${\it EP}\approx 7$-8 eV), for which neither of the excitation mechanisms mentioned above is plausible. Absorption lines of Fe II at short wavelengths are observed, and they give an explanation to the population of seven of those 21 levels (Fig. 6). These are levels belonging to the LS terms y4D, z2F and x6P (except for y4D1/2 and x6P3/2), and they are photo-excited by continuum radiation from the white dwarf through the channels a4F-y4D, a4P-z2F and a6D-x6P. Only the strongest transitions between these terms are observed as absorption lines in AG Peg, probably due to the low continuum level.


  \begin{figure}
\par\includegraphics[width=8.8cm,clip]{3396fi6.eps}
\end{figure} Figure 6: Grotrian diagram of Fe II showing the levels involved in continuum fluorescence. The dotted lines are the pumped channels while the solid lines represent decay channels observed in AG Peg.


   
Table 6: Pumped channels in ions other than Fe II.
Pumping line Pumped element Pumped transition $\lambda^{a}$ (Å)
O IV] $\lambda $1401.16 S I 3p4 3P2-(4S)5s 3S1 1401.51
N V $\lambda $1242.78 N I 2p3 2D5/2-(1D)3s 2D5/2 1243.18
N V $\lambda $1242.78 Co II 4s a5F3-4s4p y5P3 1242.49
H I $\lambda $1215.67 Co II 3d8 a3P2-(4F)5p 5D3 1213.26
H I $\lambda $1215.67 Fe III 3d6 5D4-(6S)4p 7P3 1214.57
H I $\lambda $1215.67 Fe III 3d6 5D4-(6S)4p 7P4 1213.45
continuumb Co II 3d8 3F4-4p v3D3 1187.42
a Wavelength of the pumped channel.
b Absorption at 1187 Å is observed, which explains the presence
of emission from the Co II v3D3 level.

The strong emission line $\lambda $1411.94 in AG Peg is identified as the 2p3 2P3/2-2p23s 2D5/2 transition of N I but no emission is detected from the 2p23s 2D3/2 level. We suggest that the level 2p23s 2D5/2 is selectively populated by being pumped by N V $\lambda $1242 in the absorption channel 2p3 2D5/2-2p23s 2D5/2. A similar case is $\lambda $1409.34, which is identified as a transition from the S I level (4S)5s 3S1 having a high excitation energy (8.85 eV). We suggest the S I level is pumped by O IV] $\lambda $1401. Furthermore, two pumped channels in Co II and two in Fe III have been detected in the ${\it IUE}$ spectrum of AG Peg (Table 8).

3.2.2 Parity forbidden lines

Radiative transitions between levels of the same parity must be formed by magnetic dipole (M1) or electric quadrupole (E2) interaction, which means many orders of magnitude smaller transition probabilities than electric dipole (E1) transitions including a parity change. Observations of M1 and E2 radiation from an astrophysical plasma require that the density of the plasma is low enough so the radiative lifetime of the metastable state is smaller than the time scale for deexcitation by collisional quenching. Hence, the lines from the parity forbidden transitions originate from low density regions, such as from a nebula surrounding the system. In the IUE spectra of AG Peg, 14 parity-forbidden emission lines have been identified, originating from highly-ionised elements such as Ne V and Fe VI (Table 7). The ionisation energies are very high for the ions emitting M1 and E2 radiation, which implies that all parity-forbidden radiation originates from a thin plasma, heated and ionized by the UV radiation from the white dwarf. There is a difference among the forbidden lines in IUE spectra before and after 1986. Before 1986 only six of the 14 observed parity-forbidden lines were present, and they originated from the ions O2+, Ne2+ and Ne3+. No forbidden lines from higher ionisation stages were observed. After 1986 the forbidden emission from O2+ ([O III] $\lambda $2321.66) vanished and the emission from Ne2+ ([Ne III] $\lambda $1814.63) became weaker, while eight new emission lines from Ar4+, Ne4+, Mg4+ and Fe5+ appeared in the IUE spectrum.

   
Table 7: Parity forbidden lines observed in AG Peg.
Spectrum Ionization $\lambda_{\rm lab}$ (vac). Shifta Width Transition Aij    Noteb
  (eV) (Å) (km s-1) (km s-1)   (s-1)     
[Fe VI] 75.01 1957.28 bl bl 3d3 2G7/2-3d3 2D15/2 0.91     $\uparrow$
    1944.30 17 20 3d3 2G7/2-3d3 2D13/2 12         $\uparrow$
[Mg V] 109.25 2928.0  bl bl 2p4 3P1-2p4 1D2 0.55     $\uparrow$
    2783.50 bl bl 2p4 3P2-2p4 1D2 1.90     $\uparrow$
    1324.45 45 20 2p4 3P1-2p4 1S0 23         $\uparrow$
[Ne V] 97.08 2975.66 152 51 2p2 1D2-2p2 1S0 2.60     $\uparrow$
    1575.18 124 84 2p2 3P1-2p2 1S0 4.20     $\uparrow$
[Ar V] 59.81 2692.02 41 40 3p2 3P1-3p2 1S0 6.80     $\uparrow$
[Ne IV] 63.46 2425.23 -6 18 2p3 4S3/2-2p3 2D5/2 0.00018 $\leftrightarrow$
    2422.60 -7 17 2p3 4S3/2-2p3 2D3/2 0.0053  $\leftrightarrow$
    1601.67 bl bl 2p3 4S3/2-2p3 2P1/2 0.53     $\leftrightarrow$
    1601.50 bl bl 2p3 4S3/2-2p3 2P3/2 1.33     $\leftrightarrow$
[Ne III] 40.96 1814.63 21 40 2p4 3P1-2p4 1S0 2.20     $\leftrightarrow$
[O III] 35.12 2321.66 49 25 2p2 3P1-2p2 1S0 0.22     $\downarrow$
a $\frac{\lambda_{\rm lab} - \lambda_{\rm obs}}{\lambda_{\rm lab}} \cdot 3 \times 10^{5}$; b $\downarrow$ = Only observed before 1986, $\leftrightarrow$ = observed throughout 1978 to 1995, $\uparrow$ = only observed after 1986,
bl = blend.

3.2.3 Population by recombination or collisions

Emission lines from a particular ion can originate from different regions in the symbiotic system. Still, after discarding the emission lines that originated from the white-dwarf wind before 1986 as well as all fluorescence lines and parity-forbidden lines, the remaining emission lines from a specific ion have about the same velocity shifts. The widths of these remaining emission lines did not change during 1978-1995, but the relative shift between different ions was variable. In Table 3 all ions observed in AG Peg are listed with the number of corresponding emission lines that are formed by collision or recombination, excluding the white-dwarf wind emission lines. We will now give suggestions for how and where some of those lines are formed.

A) The helium 2s 3S1- np 3P2 series

Four emission lines from the He I 2s 3S1-np 3P2 series (n=5-8) are identified in the RR Tel spectrum Penston et al. 1983. In the IUE spectra of AG Peg recorded before 1986 there are no traces of He I emission. The broad He II emission lines from the white-dwarf wind before 1986 are presumably formed by recombination. Because of the high temperature and strong UV flux in the white-dwarf wind there is no neutral helium there. However, after 1986 seven He I emission lines of the series 2s 3S1-np 3P2 ( $5 \leq n \leq 11$) are present in the spectrum as "nebular'' lines with a mean FWHM of 35 km s-1. The explanation of the He I emission is probably linked to the change of the He II lines from broad wind profiles to "narrow'' lines having an average FWHM of 49 km s-1 (see Sect. 3.1). Kenyon et al. (1993) suggest that the presence of He I is caused by heating of the red-giant atmosphere by radiation from He+ ions in a region around the white dwarf. If He II in the white-dwarf wind is responsible for He I emission from the red-giant atmosphere, then the absence of He I lines before 1986 is a problem. Another suggestion is that when the white-dwarf wind became less dense during the transition period it was not able to produce broad He II emission enough to be observed by ${\it IUE}$, but at the same time more continuum radiation from the white dwarf reached the red-giant atmosphere, ionising helium to both He+ and He2+ (Fig. 7). This implies that after 1986 both the He I and He II emission lines are formed in the red-giant atmosphere facing the white dwarf.

  \begin{figure}
\par\includegraphics[width=4.2cm,clip]{3396fi7a.eps}\hspace*{2mm}
\includegraphics[width=4.2cm,clip]{3396fi7b.eps}
\end{figure} Figure 7: Suggestion of the origin of broad He emission ( left) and narrow He emission ( right) before and after 1986 (see text).

B) The ns 2S-np 2P transitions in alkali-like spectra

It is only possible to detect the 2s 2S-2p 2P doublet transition for three species, C IV, N V, and O VI, within the wavelength regions covered by ${\it IUE}$ and ${\it FUSE}$. Atomic lithium and the ions Be+ and B2+ are too rare to be observed and for the three-electron systems heavier than oxygen the 2s-2p transition lies shortward of 900 Å. Two of the three observable doublets, C IV  $\lambda\lambda$1548.19, 1550.77 and N V $\lambda\lambda$1238.80, 1242.78 are observed as broad ($\sim$800 km s-1) emission lines that evolve into narrow emission ($\sim$40 km s-1) during the 1980s as discussed in Sect. 3.1. The O VI $\lambda $1031.92, 1037.614 resonance doublet is outside the range of ${\it IUE}$, but is observed with ${\it FUSE}$ (Fig. 8). Since ${\it FUSE}$ was launched in 1999 there have been no data on the O VI resonance doublet in AG Peg prior to the dramatic change of profile of the N V and C IV resonance doublets. However, at the base of the O VI resonance lines there are wings (FWHM $\sim$ 800 km s-1, based on Gaussian fit of the line wings in the Q1110101 spectra) indicating that the O VI doublet evolved in the same way as the C IV and N V doublets. The peak intensity of the nebular components appears to have increased from 2001 (Q1110101) to the 2003 FUSE observation (Q1110103) while the intensity of the broad underlying wind-profile decreased slightly. This could mean that the same transfer of origin of the C IV resonance doublet at the end of 1970s to the beginning of the 1980s and the N V resonance doublet during the 1980s and beginning of 1990s (Eriksson et al. 2004) is now taking place for the O VI resonance doublet.

For the iso-electronic sequence of spectra involving 11 electrons the 3s 2S-3p 2P doublets are reachable with ${\it IUE}$ for three different elements (Mg II $\lambda\lambda$2796.35, 2803.53, Al III  $\lambda\lambda$1854.72, 1862.79 and Si IV $\lambda\lambda$1393.76, 1402.77), and one with ${\it FUSE}$ (P V $\lambda\lambda$1117.98, 1128.01). The P V resonance doublet is not detected in the FUSE data probably because of a low abundance of phosphorus in the red-giant atmosphere. Energetically it would be possible since the O VI resonance doublet is observed, and the ionisation potential of O V (113.9 eV) is higher than for P IV (51.4 eV). The Si IV resonance lines evolved in the same manner as the C IV and N V resonance lines and are discussed in Sect. 3.1. The Mg II resonance doublet (Fig. 8) is known to be common in the chromospheres of red-giant stars (Kondo et al. 1976) and is probably emitted all around the red giant atmosphere. Both the Mg II and Al III resonance doublets consist of narrow emission lines throughout 1978 to 1995 and have probably never been formed in the white-dwarf wind because of the low ionisation temperature required.

  \begin{figure}
\par\includegraphics[angle=90,width=7.5cm,clip]{3396fi8a.ps}\hspa...
...pace*{2mm}
\includegraphics[angle=90,width=7.5cm,clip]{3396fi8f.ps}
\end{figure} Figure 8: The ns 2S-np 2P doublets observed in AG Peg. The figures represent the profile of the resonance doublets after the transition period in the middle of the 1980s. The resonance doublets corresponding to n = 3 (Si IV, Al III, Mg II) and C IV almost completely consist of narrow components, while the N V and O VI resonance doublets still have detectable contributions from the broad white-dwarf wind profile.

C) The ns2 1S-nsnp 3P transitions in alkaline-earth-like spectra

The spin-forbidden ns2 1S-nsnp 3P transition includes two possible intercombination lines: 1S0-3P1, which is often strong in emission in hot nebular spectra, and 1S0-3P2. Since $\Delta J = 2$ for the latter line, it can only occur via a magnetic quadrupole transition, which has a very small transition probability. Similar to the observational restrictions for the 2s 2S-2p 2P transitions discussed in the previous subsection, the 2s2 1S-2p 3P transitions can only be observed for C III], N IV] and O V]. The C III] $\lambda $1908.73 (1S0-3P1) emission line is observed as strong ( $I \sim3.5 \times 10^{-11}$ erg cm-2 s-1 Å-1) and narrow ( ${\it FWHM} \sim 35$ km s-1) in all of the IUE observations. This is probably due to the ionization energy of C III, which is too low for C2+ ions to survive in the white-dwarf wind, but the ionisation potential of C II is not too high for C2+ to be produced in the heated part of the red-giant atmosphere. At the detection limit in the longest exposed spectra at 1906.67 Å there is a weak feature ( $I \sim 30 \times 10^{-13}$ erg cm-2 s-1 Å-1), which can possibly be identified as the E2 (1S0-3P2) transition of C III] blended with Mg IV.

The N IV] $\lambda $1486.50 (1S0-3P1) emission line is a broad wind line before 1986 and is observed as a narrow emission line after 1986 as discussed in Sect. 3.1. Interestingly, the [N IV] M2 transition at 1483.32 Å is present throughout the ${\it IUE}$ observations but has a FWHM around 150 km s-1, which is very different from the FWHM of N IV] $\lambda $1486.50 both before and after 1986. Since O V has a higher ionisation energy than N IV one would also expect the O V] $\lambda $1218.34 emission line to have evolved from a broad wind profile to a narrow nebular line. However, its relative closeness to H Ly$\alpha $ at 1215.67 Å causes absorption by the neutral hydrogen in the surrounding nebula and the O V] $\lambda $1218.34 line is absent before 1986. When the temperature of the white dwarf increased the H II region expanded further out into the surrounding nebula, making it more transparent for the O V] $\lambda $1218.34 emission, which after 1986 is observed as a strong emission line.

In the Mg I iso-electronic sequence of 12-electron ions the transition 3s2 1S0-3s3p 3P1 is observed in four elements (Al II], Si III], P IV] and S V]). The S V] $\lambda $1199.04 feature evolved from a broad wind profile to a narrow nebular line during the 1980s, while Al II] $\lambda $2669.95, Si III] $\lambda $1892.03, and P IV] $\lambda $1467.43 are observed as narrow (FWHM $\sim$ 30 km s-1) throughout the time interval 1978 to 1995. The intensity ratio I(1S0-3P1)/I(1S0-3P2) has been used in C III and N IV as a diagnostic tool to obtain electron densities in AG Peg Nussbaumer & Schild 1979,Nussbaumer & Schild 1981. The same transitions can be used for O V, Al II, Si III, P IV and S V to derive complementary information about the plasma. Understanding the origin of the 1S-3P lines is therefore of great importance.

  \begin{figure}
\par\includegraphics[angle=90,width=8cm,clip]{3396fi9a.ps}\par\includegraphics[angle=90,width=8cm,clip]{3396fi9b.ps}
\end{figure} Figure 9: The intercombination multiplet 2s22p 2P-2s2p2 4P in N III] and O IV] spectra. The fine-structure component 3/2-5/2 is over-exposed in the N III] plot. The region of the N III] multiplet has not been observed by HST (GHRS) at high resolution. The dynamic range of ${\it IUE}$ was not sufficient to record spectra where the weakest N III] components are observable at the same time that N III] 3/2-5/2 is not over-exposed.

D) The excited (sp)k 2<k<8 configurations

The more ionised an element is the more sensitive the average energy of a configuration is to the principal quantum number, n. Excited states in highly-ionized spectra, for which all electrons have the same n as the ground configuration, are therefore at relatively low excitation energies. As an example the LS term 2s2p2 4P of C II is at $\sim$5.3 eV, while the LS term 2s2p3p 4P is at an energy of ($\sim$23.1 eV), i.e. more than a factor of four higher. Because of the low energy required for exciting the (sp)k configurations they can be populated through collisions. Allowed emission lines from (sp)k, 2<k<8, dominate the contribution from C II, N III, O IV, Si II, P II, P III, S II and S IV and they are also present in C III, N IV and O V. An intercombination transition, ns2np 2P-nsnp2 4P, is specially strong in N III, O IV and S IV (Fig. 9), and is also present in the Si II spectrum. The metastable nsnp2 4P is the lowest excited term in systems with five and 13 electrons and it can therefore only decay to the ground state, which explains why the corresponding multiplets are so strong. Those multiplets can be used for electron density diagnostics (Nussbaumer & Storey 1982; Nussbaumer & Storey 1979).

E) Emission lines from neutral atoms heavier than helium

Emission lines from NI, OI and SI are observed in the ultraviolet spectrum of AG Peg. Most of the emission lines from neutral elements are from allowed transitions to levels within the ground configuration, except for the ground state (Fig. 9). That the emitting gas is optically thick for transitions to the ground state indicates that the region of neutral elements is of relatively high density and low temperature (<3000 K). All of the four observed oxygen lines and five of the six observed sulphur lines correspond to transitions from np3(4S)n's 5S or 3S to the ground term np4 3P. That the 3P-5S intercombination lines of S I $\lambda $1900.29 and O I $\lambda\lambda$1355.60, 1358.51 are observed is interesting since their transition probabilities are $\sim$104 times smaller than for the 3P-3S transitions. This limits the electron density of the emitting region, presumably the outermost part of the surrounding nebula or the part of the red giant obscured from the white-dwarf emission.


  \begin{figure}
\par\includegraphics[angle=90,width=8cm,clip]{3396fi10.ps}
\end{figure} Figure 10: The O I multiplet 2p4 3P-2p3(4S)3s 3S. The component 3P2-3S1to the ground level is in absorption while the other two fine-structure components are in emission.

F) Recombination to third, fourth and fifth ionization states

The population of some levels, from which emission is observed in AG Peg, cannot be understood by collisions or any pumping mechanisms. These include levels with very high excitation energy having no known decay channels that coincide with strong UV emission lines of other elements, and exotic configurations (doubly-excited and/or involving f-electrons) rarely populated in astrophysical plasmas. If an ion is emitting lines from doubly-excited levels or levels close to the ionization energy, recombination is the most plausible explanation. Based on this reasoning we suggest recombination as the excitation mechanism for some lines. The previous discussion of the strong 2s 2S-2p 2P transitions reveals a large abundance of C IV, N V and O VI in a hot region of AG Peg, implying that recombination to C III, N IV and O V is reasonable. Both C III and O V lines have been observed from levels rarely populated by collisions and are most certainly populated by recombination (such as 4f 3F4 in C III and 5f 3F4 in O V). Although the N V $\lambda\lambda$1238.80, 1242.78 doublet is almost as strong as the C IV resonance doublet none of the observed N IV lines originate from levels that require recombination excitation. However, the N IV] $\lambda $1486.50 emission line is one of the strongest lines in the ${\it IUE}$ wavelength range, indicating high presence of N3+ ions and the N III spectrum shows a few lines, such as N III $\lambda $1387.38, with upper level 4d 2D3/2 presumably populated by recombination. Also, recombination lines of the third spectra, C III, N III and O III, were present throughout 1978-1995 and are formed in the extended red-giant atmosphere at a distance from the white dwarf sufficient to provide a temperature that gives a mixture of two and three times ionised elements.

The O V recombination lines first appeared after 1986. Before 1986, O5+ ions probably only existed in the white-dwarf wind, but after the transition period in the middle of 1980s O5+ ions were produced in the red-giant atmosphere by photo-ionisation, which explains the appearance of O V recombination lines. Four emission lines between 1669-1699 Å are identified as Mg IV lines corresponding to the multiplet (3P)3s 4P-(3P)3p 4D. These lines are the only observed Mg IV lines in the spectra of AG Peg, and the (3P)3p 4D term has an excitation energy of $\sim$75 eV. The population of these levels is likely to be due to recombination of Mg V 2p4 3P in less dense parts of the surrounding nebula since only parity forbidden lines from Mg V are observed.

   
Table 8: The relative line strengths of the Fe II multiplet a6D-z6D.
Transition $\lambda_{\rm vac}$(lab) (Å) gAa Ib
9/2-9/2 2600.17 2.39 0c
9/2-7/2 2586.65 0.37 0c
7/2-9/2 2626.45 0.75 1.23
7/2-7/2 2612.65 1.00 1.00
7/2-5/2 2599.15 0.32 0.39
5/2-7/2 2632.11 0.87 bl
5/2-5/2 2618.40 0.30 0.92
5/2-3/2 2607.87 0.45 0.61
3/2-5/2 2631.83 0.70 bl
3/2-3/2 2621.19 0.02 0.72
3/2-1/2 2614.61 0.37 0.47
1/2-3/2 2629.08 0.43 0.53
1/2-1/2 2622.45 0.12 0.52
a The gA values from Schnabel et al. (2004) are scaled in such a way that gA for the a6D7/2-z6D7/2 transition is equal to 1.00.
b The observed intensity relative to I(a6D7/2-z6D7/2) = 1.00.
c Both transitions to the ground level a6D9/2 are observed in absorption.

G) The Fe II (5D)4p levels

The lowest excited odd-parity levels in Fe II belong to the subconfiguration (5D)4p, which is built on the lowest parent term 5D of Fe III. This subconfiguration contains six LS terms (4P, 4D 4F, 6P, 6D and 6F) and accounts for 25 fine-structure levels. Transitions from (5D)4p are observed in the ultraviolet region to levels within the terms (5D)4s 6D, (5D)4s 4D, 3d7 4F and 3d7 a4P forming strong Fe II multiplets. Since transitions from all the 25 levels are observed, collisional excitation is the most likely population process. However, the decay of the (5D)5s levels, populated by the cascading decay of the H Ly$\alpha $ pumped (5D)5p levels (see Sect. 3.2.1), causes deviations in the thermal population of (5D)4p. Thus, the observed line strengths within the (5D)4s-(5D)4p and 3d7-(5D)4p multiplets are different from what is expected from their gA-values, as measured by Schnabel et al. (2004) (Table 8). Also of importance is that the transition to the ground level (5D)4s 6D9/2 is in absorption, which indicates that the optical depths also will influence the relative line strengths.

  \begin{figure}
\par\includegraphics[width=8cm,clip]{3396fi11.eps}
\end{figure} Figure 11: Figure demonstrating our idea of the excitation mechanism in Fe III and Fe II responsible for the observed octet transitions in Fe II. The presumed recombination channels are presented as dotted lines, the pumped channel as a double lines and the decay channels as solid lines. Only the levels involved in the process are plotted in this Grotrian diagram.


  \begin{figure}
\par\includegraphics[angle=90,width=8cm,clip]{3396fi12.ps}
\end{figure} Figure 12: The three O III 2p3p 3S-2p3d 3P transitions in spectrum lwp25995. Whit the dynamical range of IUE it is not sufficient to observe the 3S1-3P0 transition without having the 3S1-3P2 transition saturated because of the large difference of intensity.

H) The octet levels in Fe II

Three emission lines ( $\lambda\lambda$1926.07, 1915.62 and 1887.83) have been identified as originating from the z8P term in Fe II, which has no spin-allowed decay channels. These three lines require an explanation since the Fe II octet transitions are very rare in stellar spectra. In fact, they have only been observed in the spectrum of the sun Johansson 1977.

If Fe III is to recombine to any octet level of Fe II by electron capture the metastable septet level (6S)4s 7S3 of Fe III has to be populated. The PAR mechanism in Fe III results in population of the (6S)4p 7P levels. Furthermore, by the observed Fe III fluorescence lines at 1955.27, 1914.06 and 1895.46 Å corresponding to (6S)4s 7S-(6S)4p 7P transitions the metastable Fe III (6S)4s 7S3 level is known to be populated. In Fig. 11 our suggestion of the process leading to the Fe II octet transitions is shown.

3.3 The O III Bowen lines

The first known PAR process was the pumping of O III through the channel 2p2 3P2-2p3d 3P2 at 303.80 Å by He II Ly$\alpha $ at 303.78 Å Bowen 1934,1935. In the spectra of AG Peg emission lines corresponding to 2p3p 3S-2p3d 3P and 2p3p 3D-2p3d 3P transitions are observed, which concludes that the Bowen mechanism is active in the system. The possibility of allowed primary decays from 2p3d 3P to 2p3p 3P, which form emission lines around 3430 Å, is outside the ${\it IUE}$ range. However, all six possible emission lines corresponding to the secondary decays 2p3s 3P-2p3p 3P are observed and hence, the 2p3p 3P-2p3d 3P is certainly active. Also, two emission lines, O III $\lambda $3341.73, 3300.34 are observed as secondary decays from 2p3s 3P-2p3p 3S transitions.

It is not only the 3P2 level that is populated by PAR in AG Peg, the two other fine structure levels, 3P1 and 3P0, are also populated through channels within 2p2 3P-2p3d 3P between 303.41 Å and 303.80 Å (Eriksson et al. 2005). From the three emission lines corresponding to 2p3p 3S-2p3d 3P (Fig. 12) the relative population rate of the fine structure levels in 2p3d 3P can be estimated. The theoretical relative LS intensities for the transitions (3S1-3P2:3S1-3P1:3S1-3P0) are 100:60:20 and the observed relative intensities, which can not be measured exactly because of saturation of the strongest line, are 100: < 20: < 3. The population rate of 3P1 and 3P0 is less than for 3P2 by a factor of at least 3 and 7, respectively.

When the observed Balmer $\alpha $ and Pashen lines of He II became narrower by a factor of $\sim$20 during the middle of the 1980s the He II Ly$\alpha $ pumped O III lines also changed in appearance. In spectra recorded in 1981 and earlier the FWHM of the Bowen lines was $\sim$120 km s-1, which was a factor of $\sim$6 smaller than that of the white-dwarf wind lines but more than a factor of 3 broader than the emission lines from the nebula and the red-giant atmosphere. The FWHM of the O III Bowen lines then decreased and was $\sim$45 km s-1 in the early 1990s. The widths of the emission lines associated with the white-dwarf wind in early ${\it IUE}$ spectra decreased more rapidly during the 1980s, and the Bowen lines were actually among the broadest UV emission lines in spectra of AG Peg in the early 1990s. After 1986 the net flux of the O III Bowen lines increased by $\sim$50%. This could mean that after the He II region changed location from the white-dwarf wind to the heated part of the red-giant atmosphere more He II emission was able to reach the O2+ ions.

3.4 A line list for AG Peg

All emission features observed in this work are listed in Table 13. Lines longward of 1980 Å were observed with ${\it IUE}$ (${\it LWP}$), the lines between 1170 and 1980 Å with ${\it IUE}$ (${\it SWP}$) and the lines below 1170 were observed with ${\it FUSE}$ ( ${\it LWRS}$ and ${\it MDRS}$). In order to make comparison of line strengths useful for lines within the wavelength range of each instrument all peak intensities and FWHM are tabulated as measured in the same spectra, LWP25995 for 1980-3350 Å, SWP47715 for 1170-1980 Å and Q1110101 for lines below 1170 Å, which we call the reference spectra. A few emission features are present in spectra other than the reference spectra. These features are marked with "oth'' in the first column in the table and no information about intensity or FWHM are given in Table 14. The reference spectra were selected as such since they have the lowest noise level, which has the disadvantage that the strongest lines are saturated and no information about peak intensity or FWHM can be given in Table 13. The saturated lines are marked by "oe'' in the second column. In Cols. 4-7 the identifications of the observed lines are presented. For the unidentified lines those columns are left blank. Features that are considered to be blended with unknown features are marked with the superscript "bl'' on the measured intensity in the second column. In Col. 8 we have noted the subsection to which the reader can refer for our suggestion of the process responsible for the formation of the feature. For the wavelength intervals covered by the ${\it HST}$ (GHRS) observations Col. 9 presents the intensities.

In Table 14 all of the emission lines absent in the reference spectra are given with the observed wavelengths (Col. 1), peak intensities (Col. 2) and widths (Col. 3). The identifications are given in Cols. 4-7 as in Table 13. Column 9 lists the spectra from which the lines were measured.

Table 15 lists all of the lines that were over-exposed in the reference spectra and is constructed in the same manner as Table 14.

Table 16 is a list of the absorption lines in AG Peg. The first column gives the observed wavelength. If the wavelength is superscripted with a; the line is measured in LWP09698, b; SWP15651 and c; SWP10454, while all other lines are measured in the reference spectra. The superscript "*'' means that the line is not measured in this work but that its presence is revealed by profile fitting of the N V and C IV resonance lines (Eriksson et al. 2004). The equivalent widths of the lines are given in Col. 2 and the identifications in Cols. 3-6. In Col. 7, IS stands for interstellar line and bl for line blended by unknown contributors.

4 Nature of the emission lines in symbiotic stars

4.1 White-dwarf wind lines

A question one might ask is whether the broad wind features associated with some of the lines between 1000 and 2000 Å in AG Peg (before 1986) are unique to this star or if they are common among the symbiotic stars. To answer this question the lines showing broad wind profiles in AG Peg were analyzed for the symbiotic stars listed in Table 2. It turned out that the widths of over 400 km s-1 observed in AG Peg before 1986 are rare but not unique among these other systems, as it was observed for four of the nineteen selected symbiotic systems (PU Vul, T CrB, CH Cyg and EG And).

PU Vul is one of the symbiotic stars classified as symbiotic novae Vogel & Nussbaumer 1992, just like AG Peg. The Si IV $\lambda $1393 line shows a P Cygni profile with terminal velocity of 750 km s-1, which is similar to the white-dwarf wind velocity of AG Peg (Eriksson et al. 2004). We suggest, therefore, that the broad lines in PU Vul can be explained by a fast wind from the white dwarf triggered by the slow nova outburst. EG And is known to have a fast ($\sim$500 km s-1) wind from the white dwarf (Vogel 1993), which can explain the broad profiles underlying the narrower nebular lines in its spectrum. Interestingly, in 1995 the C IV $\lambda $1548 line displayed a P Cygni profile associated with a terminal velocity of only 114 km s-1. We have not been able to explain this absorption component but modeling of the same line in AG Peg has revealed an absorption component. This is the collision region of the white dwarf and red giant winds associated with a terminal velocity of half the white dwarf wind velocity. This should be noticed since EG And also has a region where the winds from the two stars collide (Tomov 1995). More surprising are the broad lines in T CrB and CH Cyg, since the white dwarf in these systems is known to be accreting matter from the red-giant wind (Iijima 1982; Kenyon & Garcia 1986), and therefore no white-dwarf wind is expected. The argument of matter falling into the disk surrounding the white dwarf is further strengthened here as inverted P Cygni profiles are observed in the lines C IV $\lambda $1548 (both systems) and He II $\lambda $1640 (only in T CrB). Even if we cannot explain how the lines are broadened to over 700 km s-1 the reason can be the infall of matter on the disk surrounding the white dwarf.

The 15 symbiotic systems with no trace of lines having FWHM greater than 400 km s-1 can be divided into two distinct categories with respect to the lines showing broad wind profiles in AG Peg. For eight of the stars all of those lines have FWHM between 40 and 70 km s-1, which is normal for most of the lines observed by ${\it IUE}$ in spectra of symbiotic stars. Such lines are called nebular lines and their origin being the red giant upper atmosphere irradiated by the white dwarf. For the remaining seven systems some of those emission lines have a FWHM between 110 and 140 km s-1. Common to these latter systems is that they all have underwent outbursts which could lead to an outflow of matter from the white dwarf. In Table 9 the widths of five lines associated with the white-dwarf wind in a few of the symbiotic systems is given for 20 symbiotic systems.


   
Table 9: The nature of lines having white dwarf wind profile in AG Peg in symbiotic stars.
Object He II $\lambda $1640 C IV $\lambda $1548 N IV $\lambda $1486 N V $\lambda $1238 Si IV $\lambda $1393 Comment
EG And (tcp) 52 (s, pc) 36   34 B
CH Cyg 42 (s) 730 (pc*)   321 str B
T CrB 573 (pc*) 821 (pc*) 320 788   B
PU Vul   166     982 (pc) B
V1329 Cyg 159 226       b
Z And 113 64 67 114 69 N*
RX Pup 68 128 (s) 118 111 112 N*
HBV475 142 130       N*
R Aqr   112     110 N*
HM Sge 137 111 130 131 110 N*
AG Dra 110 58 41 70 (pc) 56 N*
RW Hya 64 56 55     N
SY Mus 66 67 36 58 39 N
BF Cyg 38 65 (s, pc) 65   69 N
CI Cyg 68 44 53 55 50 N
V1016 Cyg 65 65 51 52 64 N
RR Tel 70 68 39 51 43 N
AX Per 64 52 46 58 58 N
KX Tra 69 50 36 58 54 N
AG Pega 770 (tcp, pc) (tcp) 800 (tcp) B
AG Pegb 66 45   56 36 N
N) All five lines have FWHM less than 70 km s-1.
N*) One, a few or all of the five lines have a FWHM between 120 and 150 km s-1, which is significantly broader than for the majority of lines in their spectra.
b) Two of the five lines are observable in IUE spectra of V1329 Cyg, the widths of those lines are broader than for the stars denoted N* but narrower than 400 km s-1.
B) Very broad lines (FWHM > 400 km s-1) are observed as single lines or as narrow lines superimposed on broad sockets (str).
pc) P cygni profile.
pc*) Inverted P cygni profile.
tcp = Two component profile as the spectral line has a narrow emission component superimposed on the broad white dwarf wind profile.

4.2 Fe II fluorescence

From Sect. 3.2.1 it was clear that the Fe+ ions in AG Peg are subjected to radiation from both a high-temperature region and a cool region emitting H Ly$\alpha $. Also, in RR Tel Fe II fluorescence lines are observed, pumped both by lines from highly-ionized ions and by H Ly$\alpha $(Hartman & Johansson 2000). A study of fluorescence lines in symbiotic stars (Eriksson et al. 2004) indicated that the Fe II regions in stars associated with slow nova eruptions were pumped by both H Ly$\alpha $ and high-ionization lines resulting in numerous (>10) actively pumped Fe II channels. Other symbiotic stars (with no indication of slow nova eruptions) showed fewer fluorescence lines and no H Ly$\alpha $ pumping. A special case is those objects known to have an accreting hot component, whose spectra showed no Fe II fluorescence.

In the present study ultraviolet Fe II fluorescence lines have been searched for in the symbiotic stars listed in Table 2. The presence of the Fe II lines $\lambda\lambda$2507.55, 2509.10 in emission serves as an indication of H Ly$\alpha $ pumping, while lines from the C IV pumped Fe II levels (see Table 5) serve as indicators of an Fe II region subjected to radiation from a high-ionization region. Absence of fluorescence lines in IUE data of a symbiotic star is not a sufficient reason to conclude that there is no pumping of Fe II. The lower limit of the peak intensity, for a line to be detected with the ${\it IUE}$, is around $3 \times 10^{-13}$ erg cm-2 s-1. However, in systems where the (5D)4s-(5D)4p resonance transitions but still no Fe II fluorescence lines are observed fluorescence can be ruled out or assumed to play a negligible role. Therefore, a search for Fe II lines corresponding to the a6D-z6D and a6D-z6P multiplets, which normally form the strongest Fe II lines in the IUE wavelength domain, has been carried out. The results of this search are presented in Table 10.

Among the twenty symbiotic systems considered in this study six belong to the subgroup of symbiotic slow novae: AG Peg, HM Sge, PU Vul, RR Tel, PU Vul, V1016 Cyg and V1329 Cyg. Except for HM Sge, both H Ly$\alpha $ and C IV $\lambda $1548 pumping of Fe II occurs in these systems, as observed by Eriksson et al. (2004). Emission lines in HM Sge are, in general, one magnitude fainter than in other symbiotic novae and even the Fe II resonance lines cannot be observed in the IUE spectra. This anomaly for HM Sge could indicate that it has no significant Fe II region or that the S/N ratio of ${\it IUE}$ is not high enough to see the Fe II emission.

Three of the symbiotic systems (CH Cyg, CI Cyg and T CrB) are known to have accreting disks around their hot components. As pointed out by Eriksson et al. (2004) no Fe II fluorescence can be detected in those systems. However, the Fe II resonance lines are observed in CH Cyg, which implies that there might be a Fe II region but no fluorescence in symbiotic systems involving accretion onto the hot component.

It becomes more problematic when considering the results of the 11 "normal'' symbiotic stars, which do not belong to the subgroup symbiotic novae or show any sign of a disk. Four of those systems, BF Cyg, HBV475, AG Dra and KX Tra, have no detectable Fe II emission lines in the ${\it IUE}$ spectra, and they are in a way similar to the symbiotic nova HM Sge as regards Fe II. The systems RW Hya and R Aqr show Fe II fluorescence lines from levels pumped by high-ionization lines only. However, ${\it IUE}$ spectra of the systems EG And, SY Mus, Z And and RX Pup have Fe II lines from both C IV $\lambda $1548 and H Ly$\alpha $ pumped levels. Even if neither is designated as a symbiotic nova, recurrent outbursts have been observed for Z And (Tomov et al. 2003) and RX Pup (Mikolajewska et al. 1999). This could mean that the dynamics and structure of a symbiotic system change during the outbursts (both for recurrent and slow novae) so that emission from both highly-ionized regions and H I regions can reach the Fe+ ions. Then the group of symbiotic stars having numerous fluorescence lines (Eriksson et al. 2004) would be expanded to include all symbiotic stars associated with outbursts and not only symbiotic novae. A complication to this simple idea is that outbursts also have been observed in the symbiotic stars CI Cyg and AG Dra (Belczynski et al. 2000), which do not have numerous fluorescence lines. Since CI Cyg is, as discussed in the previous paragraph, a disk-system for which no Fe II fluorescence has been observed and AG Dra is known to be metal deficient, the lack of Fe II emission lines in these two systems is no surprise. Two normal symbiotic stars seem to fall outside the established groups: SY Mus, which emits Fe II fluorescence from both H Ly$\alpha $ and C IV $\lambda $1548 pumped levels, and AX Per, which is the only symbiotic star known to emit Fe II lines only from H Ly$\alpha $ pumped levels.


 

 
Table 10: Fe II emission in symbiotic stars.
  C IV H Ly$\alpha $ (5D)4s-(5D)4p
Object pumped pumped collisionally excited
AG Peg yes yes yes
SY Mus yes yes yes
Z And yes yes yes
RX Pup yes yes yes
V1016 Cyg yes yes yes
RR Tel yes yes yes
V1329 Cyg yes yes no
PU Vul yes yes no
EG And yes yes no
CH Cyg no yes yes
RW Hya yes no no
AX Per no yes no
R Aqr no no yes
CI Cyg no no no
HBV475 no no no
T CrB no no no
HM Sge no no no
AG Dra no no no
BF Cyg no no no
KX Tra no no no


4.3 Forbidden lines

Forbidden lines indicate low density regions in astrophysical sources. In AG Peg, this low density region must be very hot since the forbidden lines belong to highly ionized atoms. As a check whether such a region with high temperature and low density is common in symbiotic stars a search was conducted for forbidden lines in the ${\it IUE}$ spectra of the other symbiotic stars. As indicators of lower temperature in the low density regions forbidden lines of N II, O I, O II and O III were selected. Forbidden lines of third to fifth spectra of the noble gases, as well as [Mg V] (observed in AG Peg) serve as indicators of high temperature. Also, the presence of [Mg VI] and [Mg VII] lines would imply an even higher temperature in the low density region than for AG Peg. A list of the forbidden lines searched for in the IUE spectra of all 20 selected symbiotic stars is given in Table 11.

Forbidden lines are detected in ${\it IUE}$ spectra for 14 of the 20 selected symbiotic stars (see Table 11). [Mg V] is seen in the spectra of eight of the symbiotic stars, and is the most frequently observed among the forbidden lines. There are four systems showing forbidden lines from magnesium: EG And, RW Hya, CH Cyg and R Aqr. EG And has forbidden lines from [O II], [Ar III] and [Ne III], RW Hya from [O III] and [Ar III], CH Cyg from [O III] and [Ar III] and R Aqr from [O II] and [O III] and [Ar III]. The absence of [Ar V] and [Ne V] in these four systems indicates that the temperature in the low density region is too low for the formation of Mg4+. The system AG Dra has only forbidden lines from [Mg VI] and [Mg VII]. The relative locations of the forbidden line regions within the symbiotic stars, and thereby the radiation field they are subjected to are poorly known. Therefore, a more detailed analysis of the forbidden line regions are not possible at this point. Assuming local thermal equilibrium, the forbidden lines observed can be explained by one region of one dominant temperature in 6 of the 14 systems showing forbidden lines (see Table 11).


   
Table 11: Forbidden lines searched for in 20 symbiotic stars.
$\lambda_{\rm vac}$ (Å) Spectra Config.a Transition Aij (s-1) Nob.
3110.08 [Ar III] 3p4 3P1-1S0 4.02 3
3071.44 [N II] 2p2 3P2-1S0 1.4 $\times$ 10-4 3
3063.72 [N II] 2p2 3P1-1S0 0.032 1
3006.10 [Ar III] 3p4 3P2-1S0 0.043 1
2993.64 [Mg V] 2p4 3P0-1D2 6.7 $\times$ 10-5 2
2975.66 [Ne V] 2p2 1D2-1S0 2.60 2
2973.15 [O I] 2p4 3P1-1S0 0.075 1
2959.23 [O I] 2p4 3P2-1S0 2.4 $\times$ 10-4 1
2928.87 [Mg V] 2p4 3P1-1D2 0.55 8
2868.99 [Ar IV] 3p3 4S3/2-2P1/2 0.97 3
2854.48 [Ar IV] 3p3 4S3/2-2P3/2 2.55 4
2786.82 [Ar V] 3p2 3P2-1S0 0.081 0
2783.50 [Mg V] 2p4 3P2-1D2 1.90 8
2692.02 [Ar V] 3p2 3P1-1S0 6.80 4
2629.92 [Mg VII] 2p2 3P2-1D2 3.39 1
2509.98 [Mg VII] 2p2 3P1-1D2 1.30 1
2471.09 [O II] 2p3 4S3/2-2P3/2 0.052 6
2470.97 [O II] 2p3 4S3/2-2P1/2 0.021 6
2442.12 [Mg VII] 2p2 3P1-1D2 1.3 $\times$ 10-4 0
2425.15 [Ne IV] 2p3 4S3/2-2D5/2 4.1 $\times$ 10-4 3
2422.51 [Ne IV] 2p3 4S3/2-2D3/2 5.3 $\times$ 10-3 4
2418.20 [Mg V] 2p4 1D1-1S0 4.20 2
2332.11 [O III] 2p2 3P2-1S0 6.3 $\times$ 10-4 1
2321.66 [O III] 2p2 3P1-1S0 0.22 5
1814.63 [Ne III] 2p4 3P1-1S0 2.20 3
1806.49 [Mg VI] 2p3 4S3/2-2D5/2 3.2 $\times$ 10-3 2
1805.94 [Mg VI] 2p3 4S3/2-2D3/2 0.12 2
1793.70 [Ne III] 2p4 3P2-1S0 5.1 $\times$ 10-3 0
1601.67 [Ne IV] 3p3 4S3/2-2P1/2 0.53 4
1601.50 [Ne IV] 3p3 4S3/2-2P3/2 1.33 4
1592.27 [Ne V] 2p2 3P2-1S0 6.8 $\times$ 10-3 0
1574.77 [Ne V] 2p2 3P1-1S0 4.20 2
a All forbidden lines in this table have the ground configuration for both upper and lower level.
b The number of symbiotic stars where the lines were observed.


   
Table 12: Forbidden spectra in symbiotic stars.
Object Spectra comm.
Z And O I, N II, Mg V  
EG And O II, Ne III, Ar III *
R Aqr O II+III, Ar III *
T CrB    
BF Cyg    
CH Cyg O II, Ar III  
CI Cyg    
AG Dra Mg VI+VII *
RW Hya O III, Ar IV *
SY Mus Ar V, Mg V  
AG Peg O III, Ne III+IV+V, Ar V, Mg V  
AX Per    
RX Pup    
HM Sge O II, Ar IV, Ne IV, Mg V  
RR Tel N II, O II+III, Ar III+IV+V, Ne III+IV+V, Mg V+VI  
KX Tra Mg V+VI *
PU Vul    
V1016 Cyg N II, O II+III, Ar IV, Ne IV, Mg V  
V1329 Cyg    
HBV475 Mg V *
* All forbidden lines in the system can be explaind by a low density region
  in local thermal equilibrium and of one dominant temperature.

5 Summary

The ultraviolet spectrum of AG Peg is indeed complex. In terms of number of lines the emission spectrum is dominated by nebular lines. Overall, the lines reflect a variety of physical processes and locations. A few emission lines are associated with the red-giant chromosphere such as Mg II $\lambda\lambda$2803.53, 2796.35 which are the strongest lines between 2000 and 3000 Å. They have a self-absorbed structure, which is typical for resonance lines. In large contrast to the red giant chromospheric lines, the AG Peg spectrum also contains parity-forbidden lines from highly-ionized ions like Ne3+ and Mg5+. These forbidden lines originate in the thin outer nebula. As an indication of the complexity of the system, intercombination and allowed lines from highly ionized ions are also observed. Most of these lines, such as Si III] $\lambda $1892.03, are excited by collisions while a few lines like O V $\lambda $1506.76 are excited by recombination. These lines are formed in the heated part of the extended red-giant atmosphere. A large number of the lines in the AG Peg spectrum are fluorescence lines, for which location of formation is not well understood. Superimposed on the spectra of nebular lines are a few broad wind lines. These lines are from highly-ionized elements and those that decay to the ground level display a P Cygni profile, showing that they are formed in the white-dwarf wind. A segment of the line-list for AG Peg can be seen in Table 13.


 

 
Table 13: A sample of the AG Peg line list.
$\lambda_{\rm obs}$ (Å) Ia Wb $\lambda_{\rm id}$ (Å) Spec. Lower level Upper level Secc Excf
2837.13 652 43 2837.14 O III 2p3p 3D3 2p3d 3P2 3 fl
      7.10 O IV 2s2p(3P)3s 4P5/2 2s2p(3P)3p 4S3/2 unk  
2836.43 46 24 2836.55 Fe II 4s b2P3/2 4p z4G5/2 2.1 fl
2833.91 50 56 2834.20 Fe II 4s a4D7/2 4p z6P5/2 2.3G col
      3.92 Fe II 4p z6P5/2 5s e6D5/2 2.1 fl
2832.28 46 26 2832.40 Fe II 4s b2P3/2 4p z2D5/2   unk
Oth     2831.76 Fe II 4s b2G7/2 4p x4G5/2 2.1 fl
2829.82 59 34 2829.91 He I 2s 3S1 6p 3P2 2.3A rec


During the 1980s the spectrum of AG Peg changed remarkably. Before 1986 six forbidden lines were observable in IUE spectra: [O III] $\lambda $2321.66, [Ne III] $\lambda $1814.63 and four [Ne IV] lines. After 1986 the [O III] line has disappeared while six new lines from four times ionized ions (Ar4+, Ne4+ and Mg4+) and two lines from Fe5+ are observed. An explanation for the change among the parity forbidden lines can be a temperature increase in the region emitting those lines. All of the 22 emission lines observed by IUE with ${\it FWHM} > 400$ km s-1 before 1986 (the white-dwarf wind lines) partially or completely disappeared after 1986 and were replaced by narrow nebular lines. The transformation of the broad wind lines occurred first for the lines of lower ionization energies and later for lines of higher ionization energies. A continuous temperature increase in the white-dwarf wind during the 1980s would explain the order in which the white-dwarf wind lines disappeared, but the temperature of the white dwarf was according to Zanstra determinations constant during the same period (Altamore & Cassatella 1997). However, a temperature increase of the wind does not mean that the temperature of the white dwarf surface increased. Eriksson et al. (2004) showed that the opacity in the white-dwarf wind for two of the wind emission lines decreased, which means that more radiation from the white dwarf reaches further into the wind. A shell in the white-dwarf wind emitting, for example, C3+ emission moves outward in the white-dwarf wind until all C3+ ions in the wind are ionized to C4+.

A few of the lines which possessed wind profiles in the spectra before 1986 are shown to be pumping Fe II channels and are thereby the cause of many of the observed Fe II fluorescence lines. When the broad wind profiles disappeared in the 1980s, only the Fe II fluorescence lines corresponding to the closest coincidances remained while the other Fe II fluorescence lines vaniched.

Observations by ${\it FUSE}$ reveal that the O VI $\lambda $1031, 1037 doublet still showed a broad wind profile in 2001. The evolution of the fluorescence lines followed that of their pumping lines. As the broad wind lines vanished so did the fluorescence lines associated with channels too far apart in wavelength from the replacing nebular lines while the fluorescence lines with very close wavelength coincidences remained in the spectrum. Fe II fluorescence lines pumped by H Ly$\alpha $ became stronger during the 1980s, indicating growth of the H II region in the system.

Many of the emission lines in spectra of AG Peg have been and surely will continue to be used for various diagnostics. When establishing diagnostics, such as for determining temperatures or densities, it is crucial to understand the nature of the lines employed.

White-dwarf winds in symbiotic stars seem to be quite rare, since broad wind profiles only could be detected in five of the 20 symbiotic systems. In the beginning we suspected that such a wind was linked to the slow nova eruption that has occurred in some of these systems. This idea must be re-considered since only two, PU Vul and AG Peg, of the five systems having broad wind profiles belong to the subclass of symbiotic novae. For seven of the other 15 symbiotic stars the FWHM of the lines show wind profiles in AG Peg are between 110-140 km s-1, while the FWHM of the same lines in the other eight symbiotic stars were 40-70 km s-1.

Except for the total lack of Fe II emission lines in the IUE spectrum of HM Sge, Fe II fluorescence lines pumped by both H Ly$\alpha $ and C IV $\lambda $1548 were observed in the symbiotic novae. Even if Fe II fluorescence lines were observed in most symbiotic stars only four of the 14 symbiotic systems with no slow nova eruption known had Fe II pumped by both H Ly$\alpha $ and C IV. Three systems in our selection have suggested accretion disks around the hot component. The spectra of these three systems showed no signs of Fe II fluorescence. During slow nova eruptions the cool H I region and a region hot enough to create ions like C3+ simultaneously are in the line of sight with the large region with Fe+ ions, while this rarely is the case for symbiotic systems under "normal'' conditions.

Acknowledgements
All of the data presented in this paper were obtained from the Multimission Archive at the Space Telescope Science Institute (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NAG-7584 and by other grants and contracts. We are grateful to the anonymous referee for a careful reading of the manuscript.

References

 

  
6 Online Material


   
Table 13F: All emission lines observed in AG Peg.
$\lambda_{\rm obs}$ (Å) Ia wb $\lambda_{\rm id}$ (Å) spec. Lower level Upper level Secc Excf $I_{\rm ghrs}^{d}$ $w_{\rm ghrs}^{e}$
3341.62 996 40 3341.73 O III 2p3s 3P2 2p3p 3S1 3 fl    
3311.70 171 21 3311.97 Fe II 4s2 c4D5/2 (5D)5p 4D5/2 2.1 fl    
Oth     3300.34 O III 2p3s 3P0 2p3p 3S1 3 fl    
3299.10 292 17                
3297.84 168 18 3297.72 He I 1s2s 1S1 1s8p 1P1 2.3A rec    
3296.86 136 20 3296.77 Fe II 4s a4D3/2 4p z6D3/2 2.3G col    
3255.69 205 38                
3249.08 225 39                
3245.18 126 18 3245.44 Fe II 3d7 d2D3/2 4p w2D3/2 2.1 fl    
3244.66 121 20 3244.66 Fe II 4s c2G9/2 4p z2F7/2   fl    
3203.97 991 61 3204.02 He II n=3 n=5 1 rec    
3163.86 97   3164.01 Fe II 3d7 a4P5/2 4p z4F5/2 2.3G col    
3162.72 91 23 3162.89 Fe II 3d7 a4P3/2 4p z4F3/2 2.3G col    
3157.15 71 42                
3154.96 133   3155.12 Fe II 4s b2G9/2 4p z2G9/2 2.1 fl    
3136.1 160 91                
3133.64 oe   3133.70 O III 2p3p 3S1 2p3d 3P2 3 fl    
3122.43 628 45 3122.54 O III 2p3p 3S1 2p3d 3P1 3 fl    
3117.23 112 36                
3116.47 82 38 3116.58 O III 2p3p 3S1 2p3d 3P0 3 fl    
3079.41 55 25 3079.57 Fe II 4p z4P5/2 5s e4D7/2 2.1 fl    
3072.44 50 21 3072.49 O IV 3s 2S1/2 3p 2P1/2   rec    
3072.05 44 19 3072.02 Fe II 4p z4P1/2 5s e4D3/2 2.1 fl    
3064.23 75   3064.32 O IV 3s 2S1/2 3p 2P3/2   rec    
3060.09 131   3060.17 O III 2p3s 3P2 2p3p 3P1 3 fl    
Oth     3049.88 Fe II 4p z4P3/2 5s e4D3/2 2.1 fl    
3047.98 oe   3047.99 O III 2p3s 3P2 2p3p 3P2 3 fl    
3043.81 90 32                
3040.62 32   3040.67 Fe II 4s2 c4D3/2 4p u4F3/2 2.1 fl    
3036.23 53   3036.30 O III 2p3s 3P1 2p3p 3P1 3 fl    
3034.26 32   3034.33 Fe II 4p z4P3/2 5s e4D1/2 2.1 fl    
3030.6 35bl   3030.57 Fe II 4s c2G9/2 4p y4H11/2 2.1 fl    
3025.74 78                  
3025.36 94   3025.42 O III 2p3s 3P0 2p3p 3P1 3 fl    
3024.26 217 50 3024.31 O III 2p3s 3P1 2p3p 3P2 3 fl    
3003.36 128bl 32 3003.52 Fe II 3d7 a4P3/2 4p z4P5/2 2.3G col    
2989.89 45 29 2989.94 Fe II 4p z4F5/2 5s e6D5/2 2.1 fl    
2988.36 66 35                
2986.38 66   2986.51 Fe II 4p z4F7/2 5s e6D7/2 2.1 fl    
      6.42 Fe II 3d7 a4P1/2 4p z4P3/2 2.3G col    
2985.63 163   2985.96 Fe II 4s2 d4P5/2 (5D)5p 4P5/2 2.1 fl    
      5.70 Fe II 3d7 a4P5/2 4p z4P5/2 2.3G col    
2984.54 149 48 2984.65 O III 2p3s 1P1 2p3p 1D2 2.3F rec    
2980.1 108   2980.22 Fe II 4s a4D1/2 4p z6F3/2 2.3G col    
      0.19 Fe II 4s2 d4P3/2 (5D)5p 4D3/2 2.1 fl    
2979.87 220   2979.95 Fe II 4s c2F5/2 4p w2D3/2 2.1 fl    
2977.23 39   2977.26 Fe II 4s a2I13/2 4p y4H11/2 2.1 fl    
2976.71 46   2976.81 Fe II 4s a4D1/2 4p z6F1/2 2.3G col    
2974.15 103 51 2975.66 [Ne V] 2p2 1D2 2p2 1S0 2.2 col    
2971.23 97 30 2971.38 Fe II 4s a4D3/2 4p z6F5/2 2.3G col    
2970.66 26   2970.80 Fe II 4s b2G7/2 4p z2F5/2   fl    
2965.6 64   2965.90 Fe II 3d7 a4P3/2 4p z4P3/2 2.3G col    
      5.53 Fe II 4s a4D3/2 4p z6F3/2 2.3G col    
      5.49 Fe II 3d7 a4P1/2 4p z4P1/2 2.3G col    
2962.05 41   2962.14 Fe II 4s a4D3/2 4p z6F1/2 2.3G col    
2960.47 61 38 2960.56 O III 2p3p 1P1 2p3d 1D2 2.3F rec    
2954.55 130 23 2954.64 Fe II 4s a4D5/2 4p z6F7/2 2.3G col    
2949.95 62bl 32 2950.04 Fe II 4s b2G7/2 4p z2F7/2   fl    
2948.40 86 28 2948.52 Fe II 3d7 a4P5/2 4p z4P3/2 2.3G col    
2945.9 113   2946.13 Fe II 4s a4D5/2 4p z6F5/2 2.3G col    
      5.97 He I 2s 3S1 5p 3P2 2.3A rec    
2945.17 74 26 2945.26 Fe II 3d7 a4P3/2 4p z4P1/2 2.3G col    
2940.23 51bl 37 2940.37 Fe II 4s a4D5/2 4p z6F3/2 2.3G col    
2937.23 184 36 2937.37 Mg II 3p 2P3/2 4s 2S1/2   unk    
2935.02 43 29                
2933.70 34 29                
2931.74 99 30                
2929.33 259   2929.49 Mg II 3p 2P1/2 4s 2S1/2   unk    
2927.29 208   2926.44 Fe II 4s a4D7/2 4p z6F9/2 2.3G col    
      8.0 [Mg V] 2p4 3P1 2p4 1D2 2.2 col    
2918.19 27   2918.32 Fe II 4s a4D5/2 4p z6P7/2 2.3G col    
2916.91 58 16 2917.01 Fe II 4s a4D7/2 4p z6F7/2 2.3G col    
2908.57 34   2908.71 Fe II 4s a4D7/2 4p z6F5/2 2.3G col    
2903.17 59 33                
2895.86 51 23                
2895.52 31 13 2895.63 Fe II 4s b4H9/2 4p z4H11/2 2.1 fl    
2893.57 59 23 2893.68 Fe II 4s a4D3/2 4p z6P5/2 2.3G col    
2892.29 30                  
2891.84 50                  
2890.40 48bl 33 2890.53 Fe II 4p z4F3/2 5s e4D5/2 2.1 fl    
2888.81 139 24 2888.94 Fe II 4s b2P3/2 4p y4P5/2 2.1 fl    
2886.89 39 20 2887.08 Fe II 4s b2H11/2 4p z4G9/2 2.1 fl    
2885.46 78 23 2885.61 Fe II 4p z4D5/2 5s e4D7/2 2.1 fl    
2884.53 55bl 36 2884.56 Fe II 4s b2H11/2 4p z4H13/2   unk    
2883.13 19bl   2883.04 Fe II 4p z4F7/2 5s e4D7/2 2.1 fl    
2882.36 80 20                
2881.60 42bl   2881.60 Fe II 4s a4D7/2 4p z6P7/2 2.3G col    
2876.08 100 26 2876.19 Fe II 4s a2F7/2 4p z2G9/2 2.1 fl    
2869.66 75   2869.72 Fe II 4s a4D5/2 4p z6P5/2 2.3G col    
2865.89 52bl 69 2866.30 Fe II 4p z4F3/2 5s e4D3/2 2.1 fl    
2865.13 51 36                
2859.40 46bl   2859.47 Fe II 4p z4D1/2 5s e4D3/2 2.1 fl    
2857.64 166 35 2857.75 Fe II 4p z4D7/2 5s e4D7/2 2.1 fl    
2856.92 94 43 2857.22 Fe II 4p z6P5/2 5s e6D7/2 2.1 fl    
      6.99 Fe II 4s a4G9/2 4p z4G9/2 2.1 fl    
2852.53 120   2852.56 Fe II 4p z4F3/2 5s e4D1/2 2.1 fl    
2850.45 44 22 2850.44 Fe II 4s a4G9/2 4p z4H11/2   unk    
2849.11 57   2849.16 Fe II 4p z4F5/2 5s e4D3/2 2.1 fl    
2848.81 44   2848.94 Fe II 4p z4D5/2 5s e4D5/2 2.1 fl    
      8.61 Fe II 4p z6P3/2 5s e6D3/2 2.1 fl    
2846.23 152 39 2846.43 Fe II 4p z4F7/2 5s e4D5/2 2.1 fl    
      6.26 Fe II 4p z4D3/2 5s e4D3/2 2.1 fl    
      6.22 Fe II 4s b4D5/2 4p x4F5/2 2.1 fl    
2844.21 67 44 2844.31 Fe II 4s b4D3/2 4p x4F5/2 2.1 fl    
      4.15 Fe II 4s b2H9/2 4p z4I9/2   unk    
2841.34 51bl   2841.49 Fe II 4s b2P1/2 4p z2D3/2   unk    
2840.26 241 24 2840.35 Fe II 4p z4F9/2 5s e4D7/2 2.1 fl    
2838.91 49 22 2839.05 Fe II 4p z6P3/2 5s e6D1/2 2.1 fl    
2837.13 652 43 2837.14 O III 2p3p 3D3 2p3d 3P2 3 fl    
      7.10 O IV 2s2p(3P)3s 4P5/2 2s2p(3P)3p 4S3/2 unk      
2836.43 46 24 2836.55 Fe II 4s b2P3/2 4p z4G5/2 2.1 fl    
2833.91 50 56 2834.20 Fe II 4s a4D7/2 4p z6P5/2 2.3G col    
      3.92 Fe II 4p z6P5/2 5s e6D5/2 2.1 fl    
2832.28 46 26 2832.40 Fe II 4s b2P3/2 4p z2D5/2   unk    
Oth     2831.76 Fe II 4s b2G7/2 4p x4G5/2 2.1 fl    
2829.82 59 34 2829.91 He I 2s 3S1 6p 3P2 2.3A rec    
2829.38 57 24 2829.46 Fe II 4s b2H11/2 4p z4I9/2   unk    
2828.17 57 30 2828.26 Fe II 4s b2H11/2 4p z4I13/2   unk    
2826.53 64bl 52 2826.58 Fe II 4s a4G11/2 4p z4G9/2 2.1 fl    
2824.06 30   2824.16 Fe II 4s a4G11/2 4p z4H13/2   unk    
2820.08 48 27 2820.17 Fe II 4s a4G11/2 4p z4H11/2   unk    
2819.43 62   2819.53 O III 2p3p 3D2 2p3d 3P2 3 fl    
2817.70 53 26 2817.92 Fe II 4p z6P5/2 5s e6D3/2 2.1 fl    
oth                    
2810.49 134 46 2810.61 Fe II 4p z6P7/2 5s e6D7/2 2.1 fl    
      0.49 O III 2p3p 3D2 2p3d 3P1 3 fl    
2808.62 31   2808.73 O III 2p3p 3D1 2p3d 3P2 3 fl    
2807.94 48bl   2808.00 Fe II 4s b4D5/2 4p y2D5/2 2.1 fl    
2806.04 31   2806.15 Fe II 4s b4D3/2 4p y2D5/2 2.1 fl    
2803.5 oe   2803.53 Mg II 3s 2S1/2 3p 2P1/2 2.3B col    
2799.60 34bl   2799.76 O III 2p3p 3D1 2p3d 3P1 3 fl    
2798.72 283 29 2798.82 Mg II 3p 2P3/2 3d 2D5/2   unk    
2796.3 oe   2796.35 Mg II 3s 2S1/2 3p 2P3/2 2.3B col    
2794.88 15   2794.96 O III 2p3p 3D1 2p3d 3P0 3 fl    
2791.49 193 36 2791.60 Mg II 3p 2P1/2 3d 2D3/2   unk    
2785.98 41   2786.12 Ne III 2p3(2D)3s 3D2 2p3(2D)3p 3D2 3.2F rec    
      6.01 Fe II 4p z6F11/2 5s e6D9/2 2.1 fl    
      5.85 Fe II 3d7 a4F3/2 4p z6D3/2 2.3G col    
2783.91 363 113 2784.51 Fe II 4s b2H11/2 4p z2G9/2 2.1 fl    
      3.50 [Mg V] 2p4 3P2 2p4 1D2 2.2 col    
2781.68 29   2781.83 O V 2s3s 3S1 2s3p 3P2 1 rec    
2780.02 44 31                
2778.80 72                  
2778.45 53bl   2778.47 Ne III 2p3(2D)3s 3D3 2p3(2D)3p 3D3 3.2F rec    
2777.62 83 21 2777.73 Fe II 4p z6F7/2 5s e6D7/2 2.1 fl    
2776.08 96 21 2776.16 Fe II 3d7 a4F5/2 4p z6D5/2 2.3G col    
2775.47 88 23 2775.55 Fe II 3d7 a4F7/2 4p z6D9/2 2.3G col    
2773.45 43 16 2773.55 Fe II 4s a4D5/2 4p z4D7/2 2.3G col    
2771.89 631 28 2772.00 Fe II 4s b2G9/2 4p y4H11/2 2.1 fl    
2770.00 104 76 2770.17 Fe II 4s a4G11/2 4p z4I13/2   unk    
      9.97 Fe II 4s a4G7/2 4p z2G9/2 2.1 fl    
2768.21 90 30 2768.33 Fe II 4p z6F9/2 5s e6D7/2 2.1 fl    
      8.23 Fe II 4p z6F3/2 5s e6D5/2 2.1 fl    
2764.40 65 49 2764.62 He I 2s 3S1 7p 3P2 2.3A rec    
2762.59 41   2762.63 Fe II 4s a4D1/2 4p z4D3/2 2.3G col    
2760.01 69bl 35 2760.15 Fe II 3d7 a4F7/2 4p z6D7/2 2.3G col    
2756.44 153 29 2756.55 Fe II 4s a4D7/2 4p z4F9/2 2.3G col    
2755.60 57 33 2755.70 Fe II 4p z6F7/2 5s e6D5/2 2.1 fl    
2753.96 56bl 42 2754.10 Fe II 4s b2H9/2 4p z2I11/2   unk    
2752.66 39bl 57 2752.96 Fe II 4p z6F3/2 5s e6D3/2 2.1 fl    
2751.77 29 23 2751.94 Fe II 4s b2P3/2 4p z2D3/2   unk    
2751.36 32 16                
2750.75 45 16                
2750.07 137 47 2750.30 Fe II 4s a4D1/2 4p z4D1/2 2.3G col    
      0.13 Fe II 4s a4D5/2 4p z4F7/2 2.3G col    
      9.99 Fe II 4s a4D3/2 4p z4D3/2 2.3G col    
2747.74 118 24 2747.79 Fe II 4s a4D5/2 4p z4D5/2 2.3G col    
2747.22 123 22 2747.30 Fe II 4s a4D3/2 4p z4F5/2 2.3G col    
2745.03 39 13 2745.08 Fe II 3d7 a4F7/2 4p z6D5/2 2.3G col    
2743.94 93 42 2794.04 Fe II 4p z6F3/2 5s e6D1/2 2.1 fl    
      4.01 Fe II 4s a4D1/2 4p z4F3/2 2.3G col    
2742.09 100 16 2742.21 Fe II 4s a2F5/2 4p y4G5/2 2.1 fl    
2740.27 141 33 2740.36 Fe II 4s a4D7/2 4p z4D7/2 2.3G col    
2737.71 41 21 2737.78 Fe II 4s a4D3/2 4p z4D1/2 2.3G col    
2734.09 oe   2734.10 He II n=3 n=6 1 rec    
2733.15 111 31 2733.26 Fe II 3d7 a4F9/2 4p z6D9/2 2.3G col    
2731.45 116 33 2731.54 Fe II 4s a4D3/2 4p z4F3/2 2.3G col    
2728.11 126 35 2728.35 Fe II 4s a4D5/2 4p z4D3/2 2.3G col    
      8.19 Fe II 4s a4G11/2 4p z2G9/2 2.1 fl    
2725.60 103 21 2725.69 Fe II 4s a4D5/2 4p z4F5/2 2.3G col    
2723.92 38 24 2724.00 He I 2s 3S1 8p 3P2 2.3A rec    
2723.39 48 17 2723.43 Fe II 4s2 d4P3/2 (4P)4sp 4P5/2 2.1 fl    
2722.77 43 17 2722.94 Fe II 4p z6P3/2 5s e4D1/2 2.1 fl    
2719.33 68 71 2719.42 Fe II 4s a2F7/2 4p y4G5/2 2.1 fl    
      9.42 Fe II 4s2 b4G5/2 (5D)5p 4D3/2 2.1 fl    
      9.16 Fe II 4s c2P1/2 (b3P)4p 4P1/2 2.1 fl    
2717.11 51 71 2717.34 Fe II 4s2 d4P5/2 (4P)4sp 4P5/2 2.1 fl    
      7.02 Fe II 4s a2F5/2 4p z2F5/2   fl    
2715.13 102 24 2715.22 Fe II 4s a4D7/2 4p z4D5/2 2.3G col    
2712.58 94 19                
2709.90 49 46 2710.18 Fe II 4s a4D5/2 4p z4F3/2 2.3G col    
      9.86 Fe II 4s b2P3/2 4p y4D5/2   fl    
2707.36 64 48 2707.37 Fe II 4s b2D5/2 4p y2P3/2   unk    
      7.14 Fe II 4p z6P5/2 5s e4D3/2 2.1 fl    
2704.77 36 21 2704.79 Fe II 4s a2F7/2 4p z2F7/2   fl    
2698.14 48 33                
2696.77 30 39 2696.92 He I 2s 3S1 9p 3P2 2.3A rec    
      6.91 N III 4s 2S1/2 5p 2P3/2 2.3F rec    
2693.54 70 28 2693.63 Fe II 4s a4D7/2 4p z4F5/2 2.3G col    
2691.65 101 40 2692.02 [Ar V] 3p2 3P1 3p2 1S0 2.2 col    
2689.93 54bl 36 2690.01 Fe II 4s b2P3/2 4p y4D3/2   fl    
2687.18 37bl   2687.27 Fe II 4s d2F7/2 4s4p x4H9/2 2.1 fl    
2686.85 26 21 2686.95 O III 2s2p2(4P)3s 5P3 2s2p2(4P)3p 5S2 2.3F rec    
2683.24 86 19 2683.30 Fe II 4s d2F3/2 4p u2G9/2 2.1 fl    
2681.56 50 34                
2679.50 43 34 2679.44 Ne III 2p3(4S)3s 3S1 2p3(4S)3p 3P1 1 rec    
2678.67 28   2678.70 Ne III 2p3(4S)3s 3S1 2p3(4S)3p 3P2 1 rec    
2677.73 102 34 2677.93 He I 2s 3S1 10p 3P2 2.3A rec    
2675.20 90 21 2675.38 O III 2s2p2(4P)3s 5P2 2s2p2(4P)3p 5S2 2.3F rec    
2669.85 436 29 2669.95 Al II] 3s2 1S0 3p 3P1 2.3C col    
2667.35 56 24                
2666.69 50 29                
2664.89 46bl   2664.99 Fe II 4s b2H9/2 4p y4G11/2   unk    
2664.01 76bl   2664.06 He I 2s 3S1 11p 3P2 2.3A rec    
2650.16 76 19 2650.26 Fe II 4s d2F5/2 4p u2G7/2 2.1 fl    
Oth     2644.55 Fe II 4s2 b4G5/2 4p x4H7/2 2.1 fl    
2639.03 85 52 2639.32 Fe II 4s2 b4G7/2 4p u2G9/2 2.1 fl    
      9.01 Fe II 4s2 b4G9/2 4p x4H11/2 2.1 fl    
2631.94 174 75 2632.11 Fe II 4s a6D5/2 4p z6D7/2 2.3G col    
      1.83 Fe II 4s a6D3/2 4p z6D5/2 2.3G col    
      1.80 Fe II 4s b4F7/2 4p z4G9/2 2.1 fl    
2630.69 43 15 2630.86 Fe II 4s b4F3/2 4p z4G5/2 2.1 fl    
2628.99 92 30 2629.08 Fe II 4s a6D1/2 4p z6D3/2 2.3G col    
2626.35 212 29 2626.45 Fe II 4s a6D7/2 4p z6D9/2 2.3G col    
2622.41 90 22 2622.45 Fe II 4s a6D1/2 4p z6D1/2 2.3G col    
2621.11 125 34 2621.19 Fe II 4s a6D3/2 4p z6D3/2 2.3G col    
2619.82 134bl 56 2619.86 Fe II 4s b4F9/2 4p z4G9/2 2.1 fl    
2618.30 160bl 46 2618.40 Fe II 4s a6D5/2 4p z6D5/2 2.3G col    
2617.62 228 26                
2614.60 82bl 69 2614.61 Fe II 4s a6D3/2 4p z6D1/2 2.3G col    
2612.56 173 29 2612.65 Fe II 4s a6D7/2 4p z6D7/2 2.3G col    
2611.83 80 34 2611.85 Fe II 4s a4D3/2 4p z4P5/2 2.3G col    
2610.79 54 22 2610.81 Ne III 2p3(2D)3s 3D3 2p3(2D)3p 3F4 3.2F rec    
2607.76 105 29 2607.87 Fe II 4s a6D5/2 4p z6D3/2 2.3G col    
2607.13 87 20                
2605.68 208 25 2605.82 Fe II 4s c2F5/2 4p v2G7/2 2.1 fl    
2599.05 68bl 50 2599.15 Fe II 4s a6D7/2 4p z6D5/2 2.3G col    
2596.34 470 27                
2592.28 72bl 35 2592.32 Fe II 4s a4D5/2 4p z4P5/2 2.3G col    
2591.21 67bl 39 2591.33 Fe II 4s b4P3/2 4p y4P5/2 2.1 fl    
2588.68 44 79 2588.95 O III] 2p3p 1P1 2p3d 3P1 3 fl    
      8.72 Fe II 4s c2G7/2 4p x2H9/2 2.1 fl    
Oth     2583.36 Fe II 4s a4D3/2 4p z4P3/2 2.3G col    
Oth     2581.94 Fe II 4p z2D5/2 5s f4F5/2 2.1 fl    
2567.13 63 33 2567.26 O III] 2p3s 3P2 2p3p 1D2 2.3F unk    
2564.68 105 28 2564.80 Co II 4s b3F3 4p z3F4   unk    
2564.23 42bl   2564.25 Fe II 4s a4D5/2 4p z4P3/2 2.3G col    
2563.17 90 20 2563.30 Fe II 4s a4D7/2 4p z4P5/2 2.3G col    
2558.00 58 70 2558.27 Fe II 4s b4F9/2 4p y4D7/2   fl    
      7.92 Fe II 4s b4F3/2 4p z2D3/2   unk    
      7.85 Fe II 4s a4H7/2 4p z4G9/2 2.1 fl    
2550.49 102 20 2550.54 Fe II 4s a2F7/2 4p x4F5/2 2.1 fl    
Oth     2549.69 Fe II 4s a2I11/2 4p x2H9/2 2.1 fl    
2549.26 111 25 2549.36 Fe II 4s a4H9/2 4p z4G9/2 2.1 fl    
2542.50 126 20 2542.60 Fe II 4s a4H7/2 4p z4G5/2 2.1 fl    
      2.58 Si III 3p 1P1 3p2 1D2   unk    
2539.40 122 20 2539.56 Fe II 4s a4H11/2 4p z4G9/2 2.1 fl    
Oth     2539.35 Fe II 4s a2F5/2 4p y2D5/2 2.1 fl    
2538.03 76 31 2538.13 Fe II 3d7 a4F5/2 4p z6F7/2 2.3G col    
      7.90 Fe II 4p z6D9/2 5s e6D9/2 2.1 fl    
2537.43 64 30 2537.61 Fe II 4s a4H11/2 4p z4H13/2   unk    
      7.57 Fe II 4s a4H9/2 4p z4H9/2   unk    
2534.49 241 26                
2531.75 89 27 2531.85 Fe II 3d7 a4F5/2 4p z6F5/2 2.3G col    
2530.94 111 24                
Oth                    
Oth     2527.06 Fe II 4s b4P5/2 4p y4P5/2 2.1 fl    
2526.60 133 15 2526.68 Fe II 4p z6D7/2 5s e6D7/2 2.1 fl    
2525.87 48bl 38 2526.15 Fe II 4s a4H13/2 4p z4H13/2   unk    
2524.87 120 20 2524.87 Si I 3p2 3P1 3p4s 3P0 2.3E unk    
2519.70 77 33 2519.96 Si I 3p2 3P1 3p4s 3P1 2.3E unk    
      9.86 Fe II 3d7 a4F7/2 4p z6F9/2 2.3G col    
      9.81 Fe II 4s a2F7/2 4p y2D5/2 2.1 fl    
2516.79 133 38 2516.87 Si I 3p2 3P2 3p4s 3P2 2.3E unk    
      6.75 Fe II 3d7 a2D3/2 4p z4G5/2 2.1 fl    
2513.96 101bl 36 2513.91 Fe II 4p z6D9/2 5s e6D7/2 2.1 fl    
2512.57 73bl   2512.81 C II 2s2p2 2P3/2 2p3 2D5/2 2.3D unk    
2511.89 529 61 2511.96 He II n=3 n=7 1 rec    
2509.77 32bl   2509.88 C II 2s2p2 2P3/2 2p3 2D3/2 2.3D unk    
2509.02 843 23 2509.10 Fe II 4s c4F7/2 (3F)4p 4G9/2 2.1 fl    
2507.46 336   2507.65 Si I 3p2 3P1 3p4s 3P2 2.3E unk    
      2507.55 Fe II 4s b4F7/2 (5D)5p 6F9/2 2.1 fl    
2507.13 192bl   2507.19 Fe II 4s c4F9/2 (3F)4p 4G9/2 2.1 fl    
2506.70 62 23 2506.85 Fe II 4s a4G9/2 4p x4G9/2   unk    
2505.94 56 30 2505.97 Fe II 3d7 a4F7/2 4p z6F5/2 2.3G col    
2498.55 134 16 2498.57 Fe II 4s a4G5/2 4p x4G5/2   unk    
2493.94 106 49 2494.05 Fe II 3d7 a4F9/2 4p z6F11/2 2.3G col    
      4.02 Fe II 4s a4H13/2 4p z4I15/2   unk    
      3.98 Fe II 4s a4G7/2 4p x4G5/2   unk    
      3.94 Fe II 4s a4H11/2 4p z4I13/2   unk    
2493.02 675 34 2493.10 Fe II 4s b2H9/2 4p y4H11/2 2.1 fl    
2484.91 143bl 35 2484.95 Fe II 3d7 a4F9/2 4p z6F9/2 2.3G col    
2484.39 80 28 2484.47 Fe II 4s c2G7/2 4p w2H9/2   unk    
2483.74 73 21                
2482.98 579 29 2483.08 Fe II 4s c2D3/2 4p w2D3/2 2.1 fl    
2481.70 628 23 2481.80 Fe II 4s b2H11/2 4p y4H11/2 2.1 fl    
2479.90 366 23 2479.98 Fe II 4s c2D5/2 4p w2D3/2 2.1 fl    
2476.96 50 25 2477.01 Fe II 4s a4H7/2 4p z2G9/2 2.1 fl    
2474.06 61bl 39 2474.20 Fe II 4s c4P5/2 (b3P)4p 4S3/2 2.1 fl    
2473.53 101bl 34 2473.66 Fe II 4s c4P5/2 (5D)5p 4D5/2 2.1 fl    
2471.06 119 16 2471.15 Fe II 3d7 a2H11/2 4p z4G9/2 2.1 fl    
2470.23 57bl 47 2470.26 Fe II 4s b4D7/2 (3D)4p 4P5/2   unk    
Oth     2464.76 Fe II 4s a4G9/2 4p x4F7/2 2.1 fl    
2459.65 87   2459.72 Fe II 4s b4D5/2 (3D)4p 4P3/2 2.1 fl    
2459.46 721 28 2459.53 Fe II 4s a4G9/2 4p y4H11/2 2.1 fl    
2458.23 121 26 2458.30 Fe II 4s b4D3/2 (3D)4p 4P3/2 2.1 fl    
2457.68 111 29 2457.71 Fe II 4s c4P5/2 (5D)5p 4P5/2 2.1 fl    
Oth     2455.71 O III 2p3s 1P1 2p3p 1S0 2.3F rec    
2448.43 140 23 2448.50 Fe II 4s a2I11/2 4p w2H9/2   unk    
Oth     2437.94 Fe II 4s a4G7/2 4p y2D5/2 2.1 fl    
2436.89 582 21 2436.96 Fe II 4s a4G11/2 4p y4H11/2 2.1 fl    
Oth     2435.69 Fe II 4s b4F3/2 4p y4G5/2 2.1 fl    
      5.66 Ne III 2p3(2D)3s 1D2 2p3(2D)3p 3P2 2.3F rec    
Oth     2429.98 Ne III 2p3(2D)3s 1D2 2p3(2D)3p 3P1 2.3F rec    
2427.85 64bl 32 2427.93 Fe II 3d7 a2H11/2 4p z4I13/2   unk    
Oth     2426.42 Fe II 4s b2P3/2 4p y2D5/2 2.1 fl    
Oth     2425.23 [Ne IV] 2p3 4S3/2 2p3 2D5/2 2.2 col    
Oth     2422.60 [Ne IV] 2p3 4S3/2 2p3 2D3/2 2.2 col    
2417.36 159 19                
Oth     2413.67 Ne III 2p3(4S)3p 3P1 2p3(4S)3d 3D2 2.3F rec    
      3.47 Ne III 2p3(4S)3p 3P2 2p3(4S)3d 3D3 2.3F rec    
2411.36 84 40 2411.25 Fe II 4s a6D3/2 4p z6F5/2 2.3G col    
2407.85 220 17 2407.96 Fe II 4s c4P1/2 (3P)4p 4S3/2 2.1 fl    
2399.87 166 16 2399.97 Fe II 4s a6D5/2 4p z6F5/2 2.3G col    
      2399.96 Fe II 3d7 a4F3/2 4p z4D5/2 2.3G col    
2396.28 172 20 2396.36 Fe II 4s a6D7/2 4p z6F9/2 2.3G col    
2395.47 94 38 2395.62 Fe II 3d7 a2H11/2 4p z2G9/2 2.1 fl    
2392.19 134 28 2392.21 Fe II 3d7 a4F7/2 4p z4F9/2 2.3G col    
2389.34 73   2389.36 Fe II 4s a6D7/2 4p z6F7/2 2.3G col    
2386.08 332 49 2386.13 He II n=3 n=8 1 rec    
2383.96 90 24 2383.97 Fe II 3d7 a4F5/2 4p z4D5/2 2.3G col    
2379.91 68bl 62 2380.00 Fe II 3d7 a4F7/2 4p z4D7/2 2.3G col    
2362.18 130 28 2362.24 Co II 4s a5F1 4p z5D2   unk    
2360.66 96 15 2360.68 Fe II 4s b2D3/2 4p w2D3/2 2.1 fl    
2359.66 131bl 27 2359.83 Fe II 4s a6D3/2 4p z6P5/2 2.3G col    
2350.86 137 29 2350.89 Si II] 3p 2P3/2 3p2 4P1/2 2.3D col    
2348.93 116 24 2349.02 Fe II 4s a6D5/2 4p z6P5/2 2.3G col    
2347.98 224 56 2348.12 Co II 4s a5F2 4p z5D2   unk    
      7.92 Fe II 3d7 d2D15/2 (b3P)4p 4S3/2 2.1 fl    
2344.94 188 24 2345.00 Fe II 4s a6D1/2 4p z6P3/2 2.3G col    
2335.15 410 19 2335.12 Si II] 3p 2P1/2 3p2 4P1/2 2.3D col    
2333.49 109bl 33 2333.52 Fe II 4s a6D7/2 4p z6P5/2 2.3G col    
2326.77 463 25 2326.84 Co II 4s a5F3 4p z5D2   unk    
2326.04 173 27                
Oth     2321.66 [O III] 2p2 3P1 2p2 1S0 2.2 col    
Oth     2316.46 Co II 4s c3F4 4p v3D3 2.1 fl    
2315.57 141 25 2315.58 Fe II 4s c4F5/2 4p u4F3/2 2.1 fl    
2311.97 282 25 2312.00 Fe II 4s c4F3/2 4p u4F3/2 2.1 fl    
2306.85 355 49 2306.91 He II n=3 n=9 1 rec    
2297.49 512 25 2297.58 C III 2s2p 1P1 2p2 1D2   unk    
2281.60 128 22 2281.73 Fe II 4s b4F9/2 4p y4H11/2 2.1 fl    
2280.55 248 22 2280.62 Fe II 4s a6D7/2 4p z4F9/2 2.3G col    
Oth     2253.83 Fe II 4s a6D7/2 4p z4F7/2 2.3G col    
2253.34 388 29 2253.34 He II n=3 n=10 1 rec    
2228.01 270 20 2228.07 Fe II 4s a4H9/2 4p y4H11/2 2.1 fl    
2220.51 487 28 2220.59 Fe II 4s a4H11/2 4p y4H11/2 2.1 fl    
2215.31 150 39 2215.36 He II n=3 n=11 1 rec    
Oth     2211.81 Fe II 4s a4H13/2 4p y4H11/2 2.1 fl    
2187.30 251 46 2187.29 He II n=3 n=12 1 rec    
Oth                    
2168.04 296 19 2168.11 Fe II 3d7 a2H11/2 4p y4H11/2 2.1 fl    
2165.93 180   2165.93 He II n=3 n=13 1 rec    
Oth                    
Oth     2149.28 He II n=3 n=14 1 rec    
2142.43 237 25 2142.46 Fe II 4s b2F5/2 4p w2D3/2 2.1 fl    
Oth     2136.03 He II n=3 n=15 1 rec    
Oth                    
Oth     2125.31 He II n=3 n=16 1 rec    
Oth     2122.12 Fe II 4s b4D3/2 4p w2D3/2 2.1 fl    
Oth     2038.11 Fe II 4s c2P3/2 (4P)4sp 2S1/2 2.1 fl    
Oth     2003.85 Fe II 4s c2P1/2 (4P)4sp 2S1/2 2.1 fl    
Oth                    
1979.04 43 29                
1978.60 43 24                
1978.29 71 17 1978.51 Fe II 4s2 b4G9/2 (2I)4sp 4H11/2 2.1 fl    
1975.36 129bl 35 1975.55 Fe II 3d7 a2G9/2 4p y4H11/2 2.1 fl    
Oth     1975.07 Fe II 3d7 a2G7/2 4p y2D5/2 2.1 fl    
1974.53 29bl 33 1974.83 Fe II 4s2 d4P3/2 (4F)4sp 6D5/2 2.1 fl    
Oth     1973.78 Fe II 4s2 b4G9/2 (2I)4sp 4H9/2 2.1 fl    
1973.32 18 20                
Oth     1972.16 Fe II 4s2 b4G11/2 (2I)4sp 4H9/2 2.1 fl    
1971.49 25bl 33 1971.63 Fe II 4s2 d4P5/2 (4F)4sp 6D5/2 2.1 fl    
1970.83 15 20 1971.03 Fe II 3d7 a2D3/2 (3D)4p 4P3/2 2.1 fl    
1970.58 17 17                
1970.02 24 18 1970.36 Fe II 3d7 a4P3/2 4p z2F5/2   fl    
1965.73 136 29 1965.92 Fe II 4s a2F5/2 4p w2D3/2 2.1 fl    
1963.99 30 20                
Oth     1957.28 [Fe VI] 3d3 2G7/2 3d3 2D15/2 2.2 col    
Oth                    
Oth                    
Oth                    
1947.41 46 14 1947.64 Fe II 4s d2G9/2 (3H)5p 4G7/2 2.1 fl    
1946.77 20   1947.00 Fe II 4s c4P5/2 (4D)4sp 4P3/2 2.1 fl    
1944.19 20 20 1944.30 [Fe VI] 3d3 2G7/2 3d3 2D13/2 2.2 col    
1943.33 19 17 1943.48 Fe III (4G)4s 5G2 (4G)4p 5H3   unk    
1941.86 26 20 1942.00 Fe II 3d7 b2F5/2 4p v2G7/2 2.1 fl    
      1.90 Fe II 4s c2P3/2 (4F)4sp 6F3/2 2.1 fl    
1940.55 20 22 1940.70 Fe II 4s d2F5/2 (4F)4sp 6F3/2 2.1 fl    
1938.51 57bl 46 1938.77 Fe II 4s c2P3/2 (4D)4sp 2P3/2   unk    
1934.30                    
1928.58 63 33                
1928.01 38 26 1928.09 Fe III (4G)4s 5G6 (4G)4p 5H5   unk    
1926.07 57 23 1926.24 Fe II 4s a6D7/2 4sp z8P5/2 2.3H rec    
Oth                    
1922.91 123 80 1923.34 C III 2s3d 3D1 2s4f 3F2 2.3F rec    
      3.16 C III 2s3d 3D2 2s4f 3F3 2.3F rec    
      2.96 C III 2s3d 3D3 2s4f 3F4 2.3F rec    
      2.79 Fe III (4G)4s 5G5 (4G)4p 5H6   unk    
Oth                    
1919.96 19 30 1920.02 O III 2p3p 1D2 2p4s 1P1 2.3F rec    
Oth                    
1915.62 28 17 1915.79 Fe II 4s a6D7/2 4sp z8P7/2 2.3H rec    
1913.89 207 33 1914.06 Fe III (6S)4s 7S3 (6S)4p 7P3 2.1 fl    
1912.72 22 27                
1911.66 16 16 1911.72 Fe II 4s2 b4G7/2 (4F)4sp 6F5/2 2.1 fl    
1911.37 30 16 1911.44 Fe II 4s2 b4G5/2 (4F)4sp 6F5/2 2.1 fl    
1910.34 25bl 53 1910.77 Fe II 4s c2P1/2 (4F)4sp 6F3/2 2.1 fl    
Oth     1909.91 Fe II 4s b4P5/2 4p y2P3/2   unk    
1908.57 oe   1908.73 C III] 2s2 1S0 2s2p 3P1 2.3C col    
1907.03 41bl 31 1907.24 Fe II 4s a4G5/2 4p w2D3/2 2.1 fl    
1906.67 19 30 1906.72 Mg IV (3P)3s 4P3/2 (3P)3p 4P1/2 2.3F rec    
      6.68 C III] 2s2 1S0 2s2p 3P2 2.3C col    
1905.58 22   1905.68 Fe II 4s c2D5/2 (5D)5p 4D5/2 2.1 fl    
1900.15 58 27 1900.29 S I] 3p4 3P2 4s 5S2 2.3E col    
1897.32 27 24 1897.55 Fe II 4s b2P3/2 4p w2D3/2 2.1 fl    
      7.48 Fe II 4s a4D5/2 4p z2D5/2   unk    
1895.31 87 35 1895.46 Fe III (6S)4s 7S3 (6S)4p 7P4 2.1 fl    
Oth     1894.29 C III 2s3p 1P1 2s4s 1S0 2.3F rec    
Oth     1893.89 Mg IV (3P)3s 4P5/2 (3P)3p 4P5/2 2.3F rec    
1891.90 oe   1892.03 Si III] 3s2 1S0 3p 3P1 2.3C col    
1890.49 88 40 1890.66 Fe III (4G)4s 5G6 (4G)4p 5F5   unk    
1889.34 26 25 1889.45 Fe III (4G)4s 5G3 (4P)4p 5D2   unk    
1888.40 26 25 1888.52 P IV 3s3p 1P1 3p2 1D2   unk    
1887.83 29 21 1888.01 Fe II 4s a6D9/2 4sp z8P9/2 2.3H rec    
1887.28 38bl   1887.45 Fe III (4G)4s 5G3 (4G)4p 5F3   unk    
1887.05 29bl   1887.20 Fe III (4G)4s 5G4 (4G)4p 5F3   unk    
1886.57 44 22 1886.76 Fe III (4G)4s 5G5 (4G)4p 5F4   unk    
1884.94 110 56 1885.22 N III 3d 2D5/2 4f 2F7/2 2.3F rec    
      5.09 Fe II 3d7 a4P5/2 4p x4F5/2 2.1 fl    
      5.06 N III 3d 2D3/2 4f 2F5/2 2.3F rec    
1883.95 60 21 1884.12 Fe II 4s2 d4P3/2 (3F)5p 4D5/2 2.1 fl    
Oth     1883.72 Fe II 4s a4D7/2 4p z4G5/2 2.1 fl    
1882.02 35 24                
Oth     1881.89 Fe II 4s a4D7/2 4p z2D5/2   unk    
Oth     1881.25 Fe II 3d7 a2P1/2 (3D)4p 4P3/2 2.1 fl    
1879.16 97 21                
Oth                    
Oth     1877.02 Fe II 4s a4G5/2 4sp x6P7/2 2.1 fl    
1874.82 32bl   1874.97 Fe II 4s a4D5/2 4p y4D7/2   fl    
1874.55 33bl   1874.58 Mg IV (3P)3s 4P5/2 (3P)3p 4P3/2 2.3F rec    
1872.44 99 48 1872.64 Fe II 4s2 b4G9/2 (2F)4sp 4G9/2 2.1 fl    
      1872.57 Fe II 4s a2S1/2 (3P)4p 4S3/2 2.1 fl    
1870.93 19 29 1871.08 Fe II 4s a4D3/2 4p z2D3/2   unk    
1869.51 92 56 1869.82 Fe III (4G)4s 5G3 (4G)4p 5F2   unk    
      9.55 Fe II 4s2 b4G11/2 (2F)4sp 4G11/2 2.1 fl    
1862.59 248 45 1862.81 Fe II 3d7 a2P3/2 (3D)4p 4P3/2 2.1 fl    
      2.79 Al III 3s 2S1/2 3p 2P1/2 2.3B col    
1856.63 48 23                
1854.53 338 55 1854.72 Al III 3s 2S1/2 3p 2P3/2 2.3B col    
Oth     1853.73 Co II 4s2 a5D2 (4F)5p 5D3 2.1 fl    
1851.65 35 26                
1851.33 30 18 1851.53 Fe II 4s a4D3/2 4p y4D5/2   fl    
Oth                    
Oth     1850.20 Fe III (4F)4s 5F4 (4F)4p 5D4   unk    
Oth     1849.40 Fe III (4F)4s 5F5 (4F)4p 5D4   unk    
1847.32 37 21 1847.48 Fe II 4s a4D7/2 4p z2G9/2 2.1 fl    
1843.10 47 21 1843.26 Fe II 4s2 b4G11/2 (4G)4sp 4G11/2 2.1 fl    
1840.04 37 38 1840.25 Co II 4s2 a5D4 (4F)5p 5D4   unk    
      0.06 Fe II 4s2 b4G7/2 (4G)4sp 4G5/2 2.1 fl    
      0.00 Fe II 4s2 b4G7/2 (4G)4sp 4G7/2 2.1 fl    
1839.63 54 41 1839.80 Fe II 4s2 b4G5/2 (4G)4sp 4G5/2 2.1 fl    
      9.74 Fe II 4s2 b4G5/2 (4G)4sp 4G7/2 2.1 fl    
1839.21 25 21 1839.27 Co II 4s2 a5D3 (4F)4p 5D3 2.1 fl    
Oth     1836.72 N I] 2p3 2P3/2 3s 4P1/2 2.3E col    
      6.71 N I] 2p3 2P1/2 3s 4P1/2 2.3E col    
Oth     1835.57 N I] 2p3 2P1/2 3s 4P3/2 2.3E col    
Oth     1834.01 N I] 2p3 2P1/2 3s 4P3/2 2.3E col    
1831.80 171 25 1836.98 Fe II 4s2 b4G7/2 (4G)4sp 4H9/2 2.1 fl    
1831.50 35bl   1831.66 Fe II 4s2 b4G9/2 (4G)4sp 4H9/2 2.1 fl    
1829.85 34 26 1829.95 Fe V (4P)4s 5P1 (4F)4p 5F2 2.3F rec    
1826.10 48 38 1826.25 S I 3p4 g3P0 4s 3S1 2.3E col    
1823.39 118 18                
1820.18 28bl   1820.34 S I 3p4 g3P1 4s 3S1 2.3E col    
1817.22 191 31 1817.45 Si II 3p 2P3/2 3p2 2D3/2 2.3D col    
1816.75 962 31 1816.93 Si II 3p 2P3/2 3p2 2D5/2 2.3D col    
Oth     1814.63 [Ne III] 2p4 3P1 2p4 1S0 2.2 col    
Oth                    
1810.15 30 20 1810.23 P II] 2p2 1S0 2s2p3 3P1 2.3D col    
Oth                    
1808.20 71 48                
1807.76 92 27 1808.01 Si II 3p 2P1/2 3p2 2D3/2 2.3D col    
1807.07 26 15 1807.31 S I 3p4 g3P2 4s 3S1 2.3E col    
1805.44 46 32 1805.67 N III 3p 2P3/2 4s 2S1/2 2.3F rec    
1803.54 77 22 1803.82 S II] 3p3 2P1/2 3p4 4P1/2 2.3D col    
Oth     1795.57 Fe II 4s2 b4G7/2 (3H)5p 4G7/2 2.1 fl    
      5.33 Fe II 4s2 b4G5/2 (3H)5p 4G7/2 2.1 fl    
      5.27 Fe II 4s2 b4G9/2 (3H)5p 4G7/2 2.1 fl    
Oth     1788.00 Fe II 4s2 a6S5/2 4sp x6P3/2 2.1 fl    
1786.58 67 40 1786.82 Si II 3d 2D3/2 3p3 2D3/2 2.3D unk    
      6.75 Fe II 4s2 a6S5/2 4sp x6P5/2   fl    
1785.12 108bl 55 1785.27 Fe II 4s2 a6S5/2 4sp x6P7/2 2.1 fl    
Oth     1783.98 Fe II 4s b4D7/2 4sp y6F7/2 2.1 fl    
Oth                    
1781.45 47 24 1781.51 Fe II 4s a4D7/2 4p y4G5/2 2.1 fl    
1780.87 74bl 45 1780.95 Fe II 4s b4D5/2 4sp y6F7/2 2.1 fl    
1779.65 51   1779.82 Fe II 4s c4P5/2 (4F)4sp 6F3/2 2.1 fl    
1768.15 264 17                
Oth     1760.82 C II 2s2p2 2D3/2 3p 2P1/2   col    
Oth     1760.47 C II 2s2p2 2D3/2 3p 2P3/2   col    
      0.40 C II 2s2p2 2D5/2 3p 2P3/2   col    
Oth     1757.74 Fe II 4s c4P3/2 (4F)4sp 6F3/2 2.1 fl    
1753.80 1482 19 1754.00 N III] 2p 2P3/2 2s2p2 4P1/2 2.3D col    
1753.32 79 36 1753.47 Mg II 3p 2P3/2 5s 2S1/2   unk    
1752.03 515bl 41 1752.16 N III] 2p 2P3/2 2s2p2 4P3/2 2.3D col    
Oth     1751.66 N III 2s2p2 2P3/2 2p3 2D5/2 2.3D unk    
Oth     1750.66 Mg II 3p 2P1/2 5s 2S1/2   unk    
1749.49 oe   1749.67 N III] 2p 2P3/2 2s2p2 4P5/2 2.3D col    
1748.51 960 24 1748.64 N III] 2p 2P1/2 2s2p2 4P1/2 2.3D col    
Oth     1747.85 N III 2s2p2 2P1/2 2p3 2D3/2 2.3D unk    
1746.61 64bl 45 1746.82 N III] 2p 2P1/2 2s2p2 4P3/2 2.3D col    
1745.08 136 36 1745.25 N I 2p3 2P3/2 3s 2P1/2 2.3E unk    
1742.60 39 34 1742.73 N I 2p3 2P3/2 3s 2P3/2 2.3E unk    
1737.40 63 50 1737.62 Mg II 3p 2P3/2 4d 2D5/2   unk    
      7.33 Co II 4s a3D3 4sp y5P3 2.1 fl    
1728.79 157bl 33 1728.85 Fe II 4s a4D3/2 4p x4F5/2 2.1 fl 37 34
1727.17 53 31 1727.38 Si IV 3d 2D3/2 4p 2P1/2   unk    
Oth     1725.98 Fe II 3d7 a2D3/2 4sp x6P3/2   fl    
1725.13 86 104 1725.36 Fe II 4s b2D5/2 (4P)4sp 4P5/2 2.1 fl    
      5.02 Fe II 3d7 a2D25/2 4p w2D3/2 2.1 fl    
      4.96 Fe II 3d7 a4F7/2 4p y4P5/2 2.1 fl    
1722.41 94 56 1722.56 Si IV 3d 2D3/2 4p 2P3/2   unk    
      2.53 Si IV 3d 2D5/2 4p 2P3/2   unk    
Oth     1721.68 C II 2s2p2 2P3/2 2p3 2P3/2 2.3D col    
1720.96 39bl 40 1721.01 C II 2s2p2 2P1/2 2p3 2P1/2 2.3D col    
1720.64 33 19 1720.85 Ne V] 2p2 1D2 2s2p3 5S2 2.3D col    
1718.34 214 145 1718.55 N IV 2p 1P1 2p2 1D2 1 rec 107 145
      8.10 Fe II 3d7 a4F5/2 4p z4G5/2 2.1 fl    
Oth     1713.00 Fe II 3d7 a4F7/2 4p z4G9/2 2.1 fl    
Oth     1706.83 Fe II 4s c2G7/2 4sp x4H7/2 2.1 fl    
1698.63 50 12 1698.78 Mg IV (3P)3s 4P3/2 (3P)3p 4D5/2 2.3F rec    
1696.47 153bl 34 1696.79 Fe II 3d7 a4F9/2 4p z4G9/2 2.1 fl    
1682.79 45 32 1683.00 Mg IV (3P)3s 4P5/2 (3P)3p 4D7/2 2.3F rec    
1682.30 114 27 1682.37 Fe II 4p z4P1/2 (3F)4d 4P3/2 2.1 fl    
1679.95 42 30 1679.96 Mg IV (3P)3s 4P3/2 (3P)3p 4D3/2 2.3F rec    
1677.67 115 18 1677.84 Fe II 3d7 a2P1/2 4p w2D3/2 2.1 fl    
1675.48 63 29 1675.71 Fe II 4p z4P3/2 (3F)4d 4P3/2 2.1 fl    
1671.35 53 25 1671.42 Fe II 4p z4P5/2 (3F)4d 4P5/2 2.1 fl    
1669.47 68 23 1669.57 Mg IV (3P)3s 4P3/2 (3P)3p 4D1/2 2.3F rec    
1666.81 158 18 1666.69 S I 3p4 1D2 (2D)4s 1D2 2.3E unk    
1666.01 oe   1666.15 O III] 2p2 3P2 2s2p3 5S2 2.3D col    
1665.14 131 31                
1660.61 oe   1660.81 O III] 2p2 3P1 2s2p3 5S2 2.3D col    
1640.07 oe   1640.35 He II n=2 n=3 1 rec 8700 82
1625.45 97bl 35 1625.58 Fe II 4s b2F5/2 4p u4F3/2 2.1 fl    
1613.83 63 39 1613.94 Fe II 4s b4D1/2 4p u4F3/2 2.1 fl    
      3.84 Fe II 4s b4D3/2 4p u4F3/2 2.1 fl    
1601.51 60 45 1601.67 [Ne IV] 2p3 4S3/2 2p3 2P1/2 2.2 col    
      1.50 [Ne IV] 2p3 4S3/2 2p3 2P3/2 2.2 col    
1601.18 71                  
1599.85 55 23 1600.01 Fe II 3d7 a2H9/2 4p v2G7/2 2.1 fl    
1589.91 79 26                
Oth     1588.29 Fe II 3d7 a4F3/2 4p x4G5/2 2.1 fl    
1579.06 90 36                
1577.84 125bl 49 1577.88 C III 2s3d 3D1 2p3d 3F2 2.3F rec    
1577.13 129 23 1577.30 C III 2s3d 3D2 2p3d 3F3 2.3F rec    
1576.37 153bl 48 1576.48 C III 2s3d 3D3 2p3d 3F4 2.3F rec    
1574.53 258 84 1575.18 [Ne V] 2p2 3P1 2p2 1S0 2.2 col    
1565.72 118 35                
1560.02 242 27 1560.25 Fe II 3d7 a4F7/2 4p x4F5/2 2.1 fl    
1553.32 225 33             137 21
1550.65 oe   1550.77 C IV 2s 2S1/2 2p 2P1/2 1 col 7570 48
1548.11 oe   1548.19 C IV 2s 2S1/2 2p 2P3/2 1 col 11650 46
Oth     1538.63 Fe II 4s a4G5/2 (5D)5p 4D3/2 2.1 fl    
1538.13 98 27 1538.16 Fe II 3d7 a4P5/2 4p w2D3/2 2.1 fl    
1537.10 324 37 1537.37 Fe II 4s c2F5/2 (3H)5p 4G7/2 2.1 fl 129 25
      7.03 Fe II 4s c2F7/2 (3H)5p 4G7/2 2.1 fl    
Oth     1534.05 O V 2p3p 1P1 2s4p 1P1 2.3F rec    
1533.25 390 35 1533.43 Si II 3p 2P3/2 4s 2S1/2   unk    
Oth                    
1515.01 44 30 1515.23 Fe II 4s b2H11/2 4sp x4H11/2 2.1 fl    
1514.20 135 30 1514.38 Fe II 4s a4G5/2 4sp x4H7/2 2.1 fl    
1512.55 235 32 1512.69 Fe II 4s a4G7/2 4sp x4H7/2 2.1 fl    
1506.75 144 52 1506.76 O V 2s4d 3D3 2s5f 3F4 2.3F rec    
1502.55 79 26 1502.69 Fe II 4s a4G5/2 4p u2G7/2 2.1 fl    
Oth     1501.76 S V 3s3p 1P1 3p2 1D2 1 unk    
1492.10 144bl 32 1492.26 Co II 4s a5P2 4sp y5P3 2.1 fl 125 24
1488.36 139 32 1438.38 Si I 3p2 1S0 3s3p3 1P1 2.3E unk    
1486.42 oe   1486.50 N IV] 2s2 1S0 2p 3P1 1 col 8290 38
1483.26 139 160 1483.32 [N IV] 2s2 1S0 2p 3P2 2.3C col 73 301
1471.93 95 26 1471.94 Fe II 4p z6D5/2 (3F)4d 4P5/2 2.1 fl    
Oth                    
1467.25 134 33 1467.43 P IV] 3s2 1S0 3p 3P1 2.3C col    
1464.68 84 29                
1459.73 98 31                
Oth     1457.76 Fe II 4s2 a6S5/2 (4D)4sp 6F3/2 2.1 fl    
1445.59 82bl 62 1445.69 Fe II 4s a2S1/2 (4F)4sp 6F3/2 2.1 fl    
1423.71 433 32 1423.79 S IV] 3p 2P3/2 3p2 4P1/2 2.3D col    
1422.37 137 25 1422.53 Fe II 4s b4D3/2 4p u4F3/2 2.1 fl    
1416.77 582 40 1416.98 S IV] 3p 2P3/2 3p2 4P3/2 2.3D col 235 36
1413.57 130 23 1413.70 Fe II 4s a4H11/2 4sp x4H11/2 2.1 fl 61 23
1411.77 1182 36 1411.94 N I 2p3 2P3/2 3s 2D5/2 2.1 fl 301 49
1409.15 106 92 1409.34 S I 3p4 3P1 (4S)5s 3S1 2.1 fl 60 51
      9.33 Co II 3d8 a3P2 4p v3D3   unk    
1407.24 1630 51 1407.38 O IV] 2p 2P3/2 2s2p2 4P1/2 2.3D col 854 42
1406.54 67 41                
1405.90 1214 36 1406.08 S IV] 3p 2P3/2 3p2 4P5/2 2.3D col 384 38
1404.65 oe   1404.80 O IV] 2p 2P3/2 2s2p2 4P3/2 2.3D col 1350 41
      4.77 S IV] 3p 2P1/2 3p2 4P1/2 2.3D col    
1402.65 oe   1402.77 Si IV 3s 2S1/2 3p 2P1/2 1 col 579 49
1401.04 oe   1401.16 O IV] 2p 2P3/2 2s2p2 4P5/2 2.3D col 3870 41
1399.61 1723 47 1399.78 O IV] 2p 2P1/2 2s2p2 4P1/2 2.3D col 1030 41
1397.96 58   1398.13 S IV] 3p 2P1/2 3p2 4P3/2 2.3D col    
1397.08 385 34 1397.23 O IV] 2p 2P1/2 2s2p2 4P3/2 2.3D col 185 56
1393.67 oe   1393.76 Si IV 3s 2S1/2 3p 2P3/2 1 col 1080 54
Oth     1393.21 Fe II 3d7 a2H11/2 4sp x4H9/2 2.1 fl    
1387.10 214 80 1387.38 N III 3p 2P3/2 4d 2D5/2 2.3F rec    
      7.26 N III 2s2p2 2S1/2 2p3 2D3/2 2.3D unk    
1385.64 129 35 1385.78 Fe II 3d7 a2P1/2 (5D)5p 4D3/2 2.1 fl    
1383.41 117 22 1383.54 Fe II 3d7 a2P3/2 (5D)5p 4D5/2 2.1 fl    
1381.08 193 30 1381.22 Fe II 4s b4P3/2 (4P)4sp 4P5/2 2.1 fl    
1376.26 67   1376.34 Fe V (4F)4s 5F5 (4F)4p 5F5 2.3F rec    
1375.56 164 33 1375.75 Fe II 3d7 a2P3/2 (5D)5p 4D3/2 2.1 fl 110 24
1373.44 69 22 1373.59 Fe V (4F)4s 5F4 (4F)4p 5F4 2.3F rec    
1372.93 209 28                
1371.18 473 83 1371.30 O V 2s2p 1P1 2p2 1D2 1 unk 214 126
      0.94 Fe V (4F)4s 5F1 (4F)4p 5F2 2.3F rec    
1367.80 89 22                
1362.60 161 22 1362.78 Fe II 4s b4P5/2 (4P)4sp 4P5/2 2.1 fl    
1360.05 184 40 1360.30 O III] 2s2p3 1P1 2p4 3P1 2.3D unk    
1358.35 298 31 1358.51 O III] 2s2p3 1P1 2p4 3P0 2.3D unk 107 24
      1358.51 O I] 2p4 3P1 3s 5S2 2.3E unk    
1355.43 406 31 1355.60 O I] 2p4 3P2 3s 5S2 2.3E unk 121 24
1345.54 99 31                
1344.80 115 45 1344.85 P III 3p 2P3/2 3p2 2D3/2 2.3D col    
1344.29 85   1344.33 P III 3p 2P3/2 3p2 2D5/2 2.3D col    
1343.41 253 34 1343.51 O IV 2s2p2 2P3/2 2p3 2D5/2 2.3D unk    
1338.47 85 38 1338.62 O IV 2s2p2 2P1/2 2p3 2D3/2 2.3D unk    
1336.71 119 63                
1335.55 315 25 1335.71 C II 2p 2P3/2 2s2p2 2D5/2 2.3D col    
1324.25 115 20 1324.45 [Mg V] 2p4 3P1 2p4 1S0 2.2 col    
1323.15 63 20                
Oth     1312.49 Fe II 4s b4D7/2 (2F)4sp 4G9/2 2.1 fl    
1310.92 58 27 1310.95 N I 2p3 2P1/2 3d 2D3/2 2.3E unk    
1310.47 60 46 1310.70 P II 3p2 3P2 3p3 3P2 2.3D col    
      0.54 N I 2p3 2P3/2 3d 2D5/2 2.3E unk    
Oth     1310.15 Fe II 3d7 a2G9/2 4p u2G9/2 2.1 fl    
1309.69 74bl   1309.87 P II 3p2 3P2 3p3 3P1 2.3D col    
1308.63 41   1308.71 C III 2p2 1S0 2s3p 1P1 2.3F rec    
1305.90 2566 46 1306.03 O I 2p4 3P0 3s 3S1 2.3E col    
1304.73 2345 46 1304.86 O I 2p4 3P1 3s 3S1 2.3E col    
1301.86 83 16 1301.87 P II 3p2 3P0 3p3 3P1 2.3D col    
1301.03 96bl   1301.15 Si III 3p 3P1 3p2 3P0 2.3D unk    
Oth     1300.86 O III] 2p2 1S0 2s2p3 3D1 2.3D col    
Oth     1298.89 Si III 3p 3P1 3p2 3P1 2.3D unk    
Oth     1296.73 Si III 3p 3P0 3p2 3P1 2.3D unk    
Oth             1      
Oth             1      
Oth             1      
1252.48 149 26                
1250.01 197 108 1250.43 Si II 3p2 2D5/2 3p3 2D5/2 2.3D unk    
      0.09 Si II 3p2 2D3/2 3p3 2D3/2 2.3D unk    
1248.20 130bl 50 1248.43 Si II 3p2 4P3/2 3p3 4S3/2 2.3D unk    
1247.25 236 29 1247.38 C III 2s2p 1P1 2p2 1S0   unk    
1242.73 oe   1242.78 N V 2s 2S1/2 2p 2P1/2 1 col 6080 67
1238.74 oe   1238.80 N V 2s 2S1/2 2p 2P3/2 1 col 9990 67
1227.70 283 73                
1218.26 2237 71 1218.34 O V] 2s2 1S0 2p 3P1 2.3F unk    
1215.65 936 106 1215.67 H I n=1 n=2   rec    
1199.04 1066 40 1199.13 S V] 3s2 1S0 3p 3P1 1 unk    
1184.43 180 28 1184.51 N III 2s2p2 2P3/2 2p3 2P3/2 2.3D unk    
Oth     1174.93 C III 2s2p 3P1 2p2 3P2   unk    
1151.04 65   1151.15 Fe II 4s a6D5/2 4s4p y6F7/2 2.1 fl    
1147.27 71   1147.41 Fe II 4s a6D7/2 4s4p y6F7/2 2.1 fl    
1145.38 1014 58 1145.58 Ne V] 2p2 3P2 2s2p3 5S2 2.3D col    
1141.22 94                  
1136.38 492 60 1136.49 Ne V] 2p2 3P1 2s2p3 5S2 2.3D col    
1128.21 96 90 1128.35 Si IV 3p 2P3/2 3d 2D5/2   unk    
      8.33 Si IV 3p 2P3/2 3d 2D3/2   unk    
1124 115pc 700                
1084.7 1940 63 1084.9 He II n=2 n=5 2.3F rec    
1067.62 227                  
1037.62 4140 116 1037.61 O VI 2s 2S1/2 2p 2P1/2 1 col    
1031.92 7970 120 1031.92 O VI 2s 2S1/2 2p 2P3/2 1 col    
974 359pc 700                
967 212pc 700                
958.51 351                  
a Peak intensity measured in 1013 erg cm-2 s-1 Å-1.
b Gaussian widths measured in km s-1.
c Reference to the section in the paper the mechanism responsible for the line is discussed.
d Intensity measured with GHRS.
e width measured with GHRS.
f Excitation mechanism, fl=fluorescence, rec=recombination, col=collision and unk=unknown excitation mechanism


   
Table 14: Intensities of emission lines not detectable with LWP25995 or SWP47715.
$\lambda_{\rm obs}$ Ia wb $\lambda_{\rm id}$ spec. Lower level Upper level spectra
3300.29 234 45 3300.34 O III 2p3s 3P0 2p3p 3S1 LWP19253
3049.78 58 18 3049.88 Fe II 4p z4P3/2 5s e4D3/2 LWP25565
2831.45 57 22 2831.76 Fe II 4s b2G7/2 4p x4G5/2 LWR06398
2817.11 52 20         LWP19253
2644.61 76 32 2644.55 Fe II 4s2 b4G5/2 4p x4H7/2 LWP09698
2583.28 144 17 2583.36 Fe II 4s a4D3/2 4p z4P3/2 LWP09698
2581.81 79 20 2581.94 Fe II 4p z2D5/2 5s f4F5/2 LWP25565
2549.69 61   2549.69 Fe II 4s a2I11/2 4p x2H9/2 LWP09698
2539.19 91   2539.35 Fe II 4s a2F5/2 4p y2D5/2 LWR06389
2528.28 89 23         LWR09130
2527.02 32   2527.06 Fe II 4s b4P5/2 4p y4P5/2 LWR09130
2464.62 62 30 2464.76 Fe II 4s a4G9/2 4p x4F7/2 LWR06398
2455.53 47   2455.71 O III 2p3s 1P1 2p3p 1S0 LWP09698
2437.89 142 28 2437.94 Fe II 4s a4G7/2 4p y2D5/2 LWP09698
2435.70 159 47 2435.69 Fe II 4s b4F3/2 4p y4G5/2 LWP09698
      5.66 Ne III] 2p3(2D)3s 1D2 2p3(2D)3p 3P2  
2429.94 61 16 2429.98 Ne III] 2p3(2D)3s 1D2 2p3(2D)3p 3P1 LWP09698
2426.32 79 16 2426.42 Fe II 4s b2P3/2 4p y2D5/2 LWR09130
2425.28 64 19 2425.23 [Ne IV] 2p3 4S3/2 2p3 2D5/2 LWP09698
2422.66 108 16 2422.60 [Ne IV] 2p3 4S3/2 2p3 2D3/2 LWP09698
2413.64 85   2413.67 Ne III 2p3(4S)3p 3P1 2p3(4S)3d 3D2 LWP09698
      3.47 Ne III 2p3(4S)3p 3P2 2p3(4S)3d 3D3  
2321.28 48 25 2321.66 [O III] 2p2 3P1 2p2 1S0 LWR09130
2316.42 53 26 2316.46 Co II 4s c3F4 4p v3D3 LWR09130
2253.78 187 37 2253.83 Fe II 4s a6D7/2 4p z4F7/2 LWR09130
2211.72 221 23 2211.81 Fe II 4s a4H13/2 4p y4H11/2 LWP25565
2179.99 619 29         LWP25565
2152.70 230 29         LWR06389
2149.26 195 45 2149.28 He II n=3 n=13 LWP09698
2136.06 158 35 2136.03 He II n=3 n=14 LWP09698
2127.87 241 24         LWR06389
2125.30 113   2125.31 He II n=3 n=15 LWR06389
2121.96 62   2122.12 Fe II 4s b4D3/2 4p w2D3/2 LWR09130
2092.38 235 19         LWR06389
2037.98 299 19 2038.11 Fe II 4s c2P3/2 (4P)4sp 2S1/2 LWR06389
2003.72 242 39 2003.85 Fe II 4s c2P1/2 (4P)4sp 2S1/2 LWR06389
2001.77 195 28         LWR06389
1974.85 32 15 1975.07 Fe II 3d7 a2G7/2 4p y2D5/2 SWP15651
1973.58 25 20 1973.78 Fe II 4s2 b4G9/2 (2I)4sp 4H9/2 SWP37477
1971.98 45 21 1972.16 Fe II 4s2 b4G11/2 (2I)4sp 4H9/2 SWP15651
1957.05 36 44 1957.28 [Fe VI] 3d3 2G7/2 3d3 2D15/2 SWP43007
1956.35 77 28         SWP43007
1951.69 34 23         SWP43007
1950.85 65 28         SWP43007
1925.70 137 25         SWP02334
1921.14 58 20         SWP15651
1919.00 30 30         SWP15651
1909.74 89 17 1909.91 Fe II 4s b4P5/2 4p y2P3/2 SWP15651
1894.16 40 17 1894.29 C III 2s3p 1P1 2s4s 1S0 SWP15651
1893.83 61 36 1893.89 Mg IV (3P)3s 4P5/2 (3P)3p 4P5/2 SWP15651
1883.71 31 19 1883.72 Fe II 4s a4D7/2 4p z4G5/2 SWP37477
1881.75 24   1881.89 Fe II 4s a4D7/2 4p z2D5/2 SWP29862
1880.99 28 19 1881.25 Fe II 3d7 a2P1/2 (3D)4p 4P3/2 SWP15651
1877.66 146 53         SWP15651
1876.94 93 16 1877.02 Fe II 4s a4G5/2 4sp x6P7/2 SWP02334
1853.52 53 31 1853.73 Co II 4s2 a5D2 (4F)4p 5D3 SWP15651
1850.50 136 26         SWP43007
1850.06 53 91 1850.20 Fe III (4F)4s 5F4 (4F)4p 5D4 SWP43007
1849.15 38 24 1849.40 Fe III (4F)4s 5F5 (4F)4p 5D4 SWP43007
1836.52 22 34 1836.72 N I 2p3 2P3/2 3s 4P1/2 SWP40149
      6.71 N I 2p3 2P1/2 3s 4P1/2  
1835.37 27 21 1835.57 N I 2p3 2P3/2 3s 4P3/2 SWP40149
1833.83 29 20 1834.01 N I 2p3 2P1/2 3s 4P3/2 SWP40149
1814.50 51 40 1814.63 [Ne III] 2p4 3P1 2p4 1S0 SWP15651
1813.85 41 18         SWP43007
1809.84 101 22         SWP43007
1795.30 94 52 1795.57 Fe II 4s2 b4G7/2 (3H)5p 4G7/2 SWP15651
      5.33 Fe II 4s2 b4G5/2 (3H)5p 4G7/2  
      5.27 Fe II 4s2 b4G9/2 (3H)5p 4G7/2  
1787.79 49 22 1788.00 Fe II 4s2 a6S5/2 4sp x6P3/2 SWP37477
1783.88 99 44 1783.98 Fe II 4s b4D7/2 4sp y6F7/2 SWP10454
1782.64 42 49         SWP43007
1760.78 40 32 1760.82 C II 2s2p2 2D3/2 3p 2P1/2 SWP29862
1760.26 103 49 1760.47 C II 2s2p2 2D3/2 3p 2P3/2 SWP29862
      0.40 C II 2s2p2 2D5/2 3p 2P3/2  
1757.61 46 22 1757.74 Fe II 4s c4P3/2 (4F)4sp 6F3/2 SWP43007
1751.45 47 33 1751.66 N III 2s2p2 2P3/2 2p3 2D5/2 SWP15651
1750.46 65 41 1750.66 Mg II 3p 2P1/2 5s 2S1/2 SWP40149
1747.64 36   1747.85 N III 2s2p2 2P1/2 2p3 2D3/2 SWP15651
1725.78 141 17 1725.98 Fe II 3d7 a2D3/2 4sp x6P3/2 SWP15651
1721.46 102 23 1721.68 C II 2s2p2 2P3/2 2p3 2P3/2 SWP10454
1712.99 56 18 1713.00 Fe II 3d7 a4F7/2 4p z4G9/2 SWP43007
1706.78 164 19 1706.83 Fe II 4s c2G7/2 4sp x4H7/2 SWP15651
1588.07 167 21 1588.29 Fe II 3d7 a4F3/2 4p x4G5/2 SWP06355
1538.59 152 18 1538.63 Fe II 4s a4G5/2 (5D)5p 4D3/2 SWP29862
1533.8 170   1534.05 O V 2p3p 1P1 2s4p 1P1 SWP29862
1531.0 232 127         SWP29862
1502.0 429 937 1501.76 S V 3s3p 1P1 3p2 1D2 SWP02334
1468.88 103 49         SWP29862
1457.53 163 23 1457.76 Fe II 4s2 a6S5/2 (4D)4sp 6F3/2 SWP15651
1392.99 195 24 1393.21 Fe II 3d7 a2H11/2 4sp x4H9/2 SWP02334
1312.41 94 16 1312.49 Fe II 4s b4D7/2 (2F)4sp 4G9/2 SWP29862
1310.01 184 27 1310.15 Fe II 3d7 a2G9/2 4p u2G9/2 SWP06355
1300.75 145 16 1300.86 O III] 2p2 1S0 2s2p3 3D1 SWP15651
1298.78 120 30 1298.89 Si III 3p 3P1 3p2 3P1 SWP29862
1296.58 90 19 1296.73 Si III 3p 3P0 3p2 3P1 SWP29862
1265.98 858 554         SWP02334
1260.40 1556 699         SWP02334
1253.26 1469 789         SWP02334
1174.86 399 41 1174.93 C III 2s2p 3P1 2p2 3P2 SWP15651
a Peak intensity measured in 1013 erg cm-2 s-1 Å-1.
b Gaussian widths measured in km s-1.


   
Table 15: Emission lines saturated in LWP25995 or SWP47715.
$\lambda_{\rm obs}$ Ia wb $\lambda_{\rm id}$ spec. Lower level Upper level spectra
3133.62 3204 49 3133.70 O III 2p3p 3S1 2p3d 3P2 LWP21635
3047.86 805 34 3047.99 O III 2p3s 3P2 2p3p 3P2 LWP30936
2803.5 717   2803.53 Mg II 3s 2S1/2 3p 2P1/2 LWP21635
2796.3 828   2796.35 Mg II 3s 2S1/2 3p 2P3/2 LWP21635
2734.00 596 54 2734.10 He II n=3 n=5 LWP19253
1908.65 3389 36 1908.73 C III 2s2 1S0 2s2p 3P1 SWP55055
1891.96 5239 29 1892.03 Si III 3s2 1S0 3p 3P1 SWP55055
1749.55 2077 36 1749.67 N III 2p 2P3/2 2s2p2 4P5/2 SWP55055
1666.06 8540 38 1666.15 O III] 2p2 3P2 2s2p3 5S2 SWP55055
1660.70 3540 34 1660.81 O III] 2p2 3P1 2s2p3 5S2 SWP55055
1640.28 22040 60 1640.35 He II n=2 n=3 SWP55055
1550.79 24420 45 1550.77 C IV 2s 2S1/2 2p 2P1/2 SWP55055
1548.21 44470 37 1548.19 C IV 2s 2S1/2 2p 2P3/2 SWP55055
1486.42 14200 32 1486.50 N IV 2s2 1S0 2p 3P1 SWP55055
1404.74 2389 26 1404.80 O IV] 2p 2P3/2 2s2p2 4P3/2 SWP55055
      4.77 S IV 3p 2P1/2 3p2 4P1/2  
1402.78 2439 36 1402.77 Si IV 3s 2S1/2 3p 2P1/2 SWP55055
1401.07 7500 43 1401.16 O IV] 2p 2P3/2 2s2p2 4P5/2 SWP55055
1393.75 3796 37 1393.76 Si IV 3s 2S1/2 3p 2P3/2 SWP55055
1242.78 12570 56 1242.78 N V 2s 2S1/2 2p 2P1/2 SWP55055
1238.79 19560 70 1238.80 N V 2s 2S1/2 2p 2P3/2 SWP55055
a Peak intensity measured in 1013 erg cm-2 s-1 Å-1.
b Gaussian widths measured in km s-1.


   
Table 16: Aborption lines in AG Peg.
$\lambda_{\rm obs}$ ekvi $\lambda_{\rm id}$ spec. Lower level Upper level shift rem
2852.92 0.21 2852.96 Mg I 3s2 1S0 3s3p 1P1 IS  
2606.49a 0.26 2606.46 Mn II 4s a7S3 4p z7P2    
2600.13 0.20 2600.17 Fe II 4s a6D9/2 4p z6D9/2    
2594.51 0.17 2594.50 Mn II 4s a7S3 4p z7P3    
2586.68 0.37 2585.65 Fe II 4s a6D9/2 4p z6D7/2    
2576.88 0.14 2576.87 Mn II 4s a7S3 4p z7P4    
2514.83 0.21 2515.07 Si I 2p2 3P0 2p3s 3P1    
2382.75 0.26 2382.77 Fe II 4s a6D9/2 4p z6F11/2    
2374.55 0.20 2374.46 Fe II 4s a6D9/2 4p z6F9/2    
1969.90b 0.15 1970.36 Fe II 3d7 a4P3/2 4p z2F5/2    
1913.26 0.15 1913.25 Fe I 4s2 a5D3 (2D)4p 3D2    
1859.44 0.18            
1838.34b 0.21            
1801.49 0.15            
1788.61 0.21            
1737.82 0.13            
1719.41b 0.23 1720.03 Fe II 3d7 a4P1/2 (3D)4p 4P3/2    
1670.76 0.37 1670.99 Fe II 3d7 a4F3/2 4p y4D3/2    
    0.79 Al II 2s2 1S0 3p 1P1    
    0.79 Fe II 3d7 a4F5/2 4p y4D5/2    
    0.75 Fe II 3d7 a4F9/2 4p y4D7/2    
1658.97 0.12 1659.48 Fe II 3d7 a4F7/2 4p y4D5/2    
1656.82 0.21 1657.07 Fe II 3d7 a4F3/2 4p x4D3/2    
    6.93 C I 2p2 3P0 2p3s 3P1 IS  
1642.33 0.11 1642.37 Fe II 4s a6D9/2 4p z4H11/2    
1608.34 0.31 1608.45 Fe II 4s a6D9/2 4sp y6P7/2    
1558.97 0.23 1559.09 Fe II 3d7 a4F9/2 4p x4F9/2    
1558.51 0.14 1558.54 Fe II 3d7 a4F5/2 4p y2D5/2    
1548.56* 0.04 1548.70 Fe II 3d7 a4F7/2 4p y2D5/2    
1548.27* 0.02 1548.41 Fe II 3d7 a4P1/2 4p w2D3/2    
1548.06* 0.02 1548.20 Fe II 3d7 a4F9/2 4p y4H11/2    
1526.64 0.16 1526.71 Si II 3p 2P1/2 4s 2S1/2    
1470.35c 0.10            
1470.08c 0.15            
1401.50 0.06 1401.51 S I 3p4 3P2 (4S)5s 3S1    
1334.40 0.22 1334.53 C II 2p 2P1/2 2s2p2 2D3/2 IS  
1328.71 0.15 1328.83 C I 2p2 3P0 2s2p3 3P1 IS  
1304.35 0.07 1304.49 P II 3p2 3P1 3p3 3P0    
1304.19 0.09 1304.37 Si II 3p 2P1/2 3p2 2S1/2    
1302.12 0.10 1302.12 O I 2p4 3P2 3s 3S1 IS  
1277.14 0.21 1277.28 C I 2p2 3P1 2p3d 3D2 IS  
    7.25 C I 2p2 3P0 2p3d 3D1 IS  
1260.35 0.16 1260.53 Fe II 4s a6D9/2 4sp x6P7/2    
    1260.42 Si II 3p 2P1/2 3d 2D3/2    
1259.41 0.23 1259.52 S II 3p3 4S3/2 3p4 4P5/2    
1253.70 0.21 1253.81 S II 3p3 4S3/2 3p4 4P3/2    
1250.47 0.24 1250.58 S II 3p3 4S3/2 3p4 4P1/2    
1242.63* 0.03 1242.74 Fe II 3d7 a4F5/2 4p v2G7/2    
1206.39 0.10 1206.50 Si III 3s2 1S0 3p 1P1    
1200.64b 0.14 1200.71 N I 2p3 4S3/2 3s 4P5/2 IS  
1200.16b 0.18 1200.23 N I 2p3 4S3/2 3s 4P3/2 IS  
1199.48b 0.13 1199.55 N I 2p3 4S3/2 3s 4P1/2 IS  
1193.19 0.11 1193.29 Si II 3p 2P1/2 3p2 2P1/2    
1190.29b 0.14 1190.42 Si II 3p 2P1/2 3p2 2P3/2    
1187.42 0.05 1187.42 Co II 3d8 a3F4 4p v3D3    
1134.96 0.18 1134.97 N I 2p3 4S3/2 2p4 4P5/2 IS  
1134.28 0.45 1134.42 N I 2p3 4S3/2 2p4 4P3/2 IS  
    4.17 N I 2p3 4S3/2 2p4 4P1/2 IS  
1122.42 0.98            
1110.10 0.19 1110.28 Fe II 4s a6D9/2 (5D)5p 6F9/2    
1108.45 0.66 1108.51 Fe II 3d7 a4F3/2 4p u4F3/2 bl  
1094.06 0.28 1094.08 Fe II 3d7 a4F7/2 (4D)4s4p 6D5/2    
1092.37 0.44            
1078.97 0.31            
1077.34 0.58            
1064.63 0.25            
1063.11 0.59 1063.18 Fe II 4s a6D9/2 (4D)4s4p 6D9/2 bl  
1051.15 0.38            
1049.50 0.59            
1040.31 0.13            
1039.17 0.15 1039.23 O I 2p4 3P2 2p3 (4S)4s 3S1 IS  
1038.62 0.11            
1038.09 0.15            
1014.33 0.14            
1012.90 0.40            
1009.76 0.15            
1008.53 0.28            
974.06 0.10 974.07 O I 2p4 3P2 (2D)3s 1D2 IS  
973.22 0.10 973.23 O I 2p4 3P1 (4S)4d 3D2    
i Equivalent width measured in Å.



Copyright ESO 2006