The low resolution spectrum, shown in Fig. 1, shows typical features of a
symbiotic star, viz. Balmer emissions with steep decrement, which are
signatures of the hot component, and TiO bands, probably originating in
the cool atmosphere of a red star. In addition to the features seen by
Kilkenny (1997), we find Fe I, He I and Fe II
emissions, and most notably the Ca II 8498, 8542, 8662 triplet in
emission. Based on the wavelengths, and the absence of Paschen 14, we
suspect that these emissions are truly Ca II and not the Paschen
P13, P15 and 16 lines. The emissions at
4730, 5197 and 6384 Å
are tentatively identified as Mn I whereas
5991 and 6300
Å probably correspond to O I. The narrow absorption lines of
the cool-star, often seen in symbiotics, do not appear in our spectrum.
The H
emission wings extend to velocities
1000 kms-1. The spectral characteristics described above, especially the
presence of the Ca II triplet in emission and the absence of
He II emission, places V589Sgr as a special member in the
class of symbiotic stars. The steep Balmer decrement, and the absence of
He II4686 emission, implies a temperature for the hot component
lower than in other members of the class.
Line |
![]() |
rv (kms-1) |
H![]() |
-143 | 13 |
H![]() |
-40 | 40 |
H![]() |
-21 | 11 |
H![]() |
-9 | -46 |
H![]() |
-8 | -162 |
He I 5875 | -8 | 14 |
He I 5015 | -10 | 105 |
He I 4922 | -9 | 60 |
Ca II 8662 | -1 | |
Ca II 8542 | -4 | |
Ca II 8498 | -7 | |
Mn I 4730 | -5 | 4 |
Mn I 5197 | -5 | -2 |
Mn I 6384 | -1 | -3 |
Fe I 4384 | -6 | 15 |
Fe I 4490 | -6 | 8 |
Fe I 4602 | -1 | 28 |
Fe I 5168 | -6 | 17 |
Fe II 4628 | -4 | 7 |
Fe II 5362 | -2 | 18 |
Fe II 6433 | -2 | 6 |
Fe II 6456 | -2 | 8 |
Fe II 6516 | -3 | 17 |
Fe I + Fe II 4232 | -5 | |
Fe I + Fe II 4414 | -10 | |
Fe I + Fe II 5316 | -5 | |
Fe I + Fe II 6417 | -1 | |
O I 5991 | -2 | -5 |
O I 6300 | -3 | 19 |
unknown 4618 | -2 | |
unknown 4666 | -3 | |
unknown 5234 | -4 | |
unknown 5275 | -3 | |
unknown 5534 | -2 | |
unknown 6147 | -2 | |
unknown 6317 | -2 | |
unknown 7633 | -10 |
Table 1 lists the equivalent width and the radial velocity for the main
spectral lines. Heliocentric radial velocities were measured by fitting
Gaussian functions to the profiles whereas the equivalent width
was obtained by integration of the flux between the points where the
profile merges with the continuum. Since the spectrum shows strong
gradients and severe line blending, it is not an elementary task to determine
the continuum, so the errors associated to the equivalent widths can be of
order of 30% for the weaker lines but certainly much lower for the stronger lines
(5% for H
for instance).
From Table 1 the mean radial velocities are:
= 22
14 kms-1 (3 lines),
=
67
42 kms-1 (3 lines),
= 17
7 kms-1 (4 lines),
= 13
5 kms-1 (5 lines)
and
= 7
12 kms-1 (2 lines). The errors reflect the
root mean square of the averages. Several lines cannot be identified.
Possible causes are line blending or existence of lines of high
excitation ions. The radial velocities here reported were measured on the
grism #7 spectrum, since
this spectrum provided the best set of radial velocities, compared
with the spectra taken with lower resolution grisms. For this reason
we do not give velocities of lines with
> 6900 Å, since
these measurements showed a great scatter.
The above average of H I velocities does not consider the low
velocity H
and H
lines, since these lines are likely
contaminated with Fe I and Fe II and might suffer of
wavelength calibration biases on the CCD blue edge. The velocities
reported here are different from those given by Kilkenny (1997), viz.
kms-1 and
kms-1. A long-term study is necessary to confirm the radial
velocity variability of this star.
© ESO 2001