2 The ultraviolet spectra of the Pop II A-type stars

Ultraviolet data are the low-resolution IUE spectra extracted from the version 3.0 of the INES (IUE newly extracted spectra) archive (INES 2000), as available at the website http://ines.vilspa.esa.es. We used only low-resolution, large-aperture spectra. When more than one image was available for a given wavelength range, we selected the best one according to the exposure classification code (ECC). Highest weight was given to ECC=500. In order to obtain only one spectrum, the selected long-wavelength spectrum was joined to the selected short-wavelength spectrum at 1978 Å. The stars and the adopted spectra, together with their ECC, are listed in Table 1. The V magnitude given in Col. 2 of Table 1 was taken from KCC. The last four columns of Table 1 give the abundance [Fe/H] relative to the Sun, the effective temperature $T_{\rm eff}$, the gravity $\log\,g$, and the microturbulent velocity $\xi$, which were obtained by KCC from their analysis of the stars.

Not all the IUE spectra are of good quality and there are only four stars out of the twenty-nine of the sample which have spectra with ECC=500 for both short- and long-wavelength regions. However, for one of them, HD 106304, the flux of the long-wavelength region is much lower than that of the short-wavelength region (Fig. A.3, Appendix A), in spite of both spectra having been classified as "good'' in accordance with their ECC. As a consequence, we have used only the short-wavelength energy distribution for our analysis of HD 106304. The example of HD 106304 may lead us to suspect that some difference between the flux levels of the short- and long-wavelength regions may exist also for other stars, although less conspicuous than that observed for HD 106304, all the more that most of the stars have spectra of different quality for the two ranges.

 

 

Table 1: The sample of the A-type stars, the adopted IUE images, and stellar parameters from KCC.

Star	V	image	ECC	image	ECC	[Fe/H]	$T_{\rm eff}$	$\log\,g$	$\xi$
HD 2857	9.990	SWP56216	500	LWR08070	403	[-1.73]	7550	3.00	3.0
HD 4850	9.619	SWP55936	500	LWP31488	500	[-1.27]	8450	3.20	2.0
HD 8376	9.655	SWP56274	500			[-2.95]	8150	3.30	1.0
HD 13780	9.811	SWP56045	500	LWP31406	501	[-1.45]	7950	3.10	2.0
HD 14829	10.306	SWP23439	503	LWP31398	503	[-2.39]	8900	3.20	2.0
HD 31943	8.262	SWP55928	500	LWP23521	402	[-0.99]	7900	3.20	4.0
HD 60778	9.103	SWP07351	502	LWR06342	XX1	[-1.49]	8050	3.10	3.0
HD 74721	8.713	SWP08061	n/a	LWR07028	501	[-1.42]	8900	3.30	4.0
HD 78913	9.285	SWP45164	400	LWP23522	502	[-1.43]	8500	3.25	2.0
HD 86986	8.000	SWP03931	n/a	LWR03502	n/a	[-1.81]	7950	3.20	2.5
HD 87047	9.725	SWP54441	400	LWP30460	500	[-2.47]	7850	3.10	2.0
HD 87112	9.717	SWP54452	500			[-1.46]	9750	3.50	2.0
HD 93329	8.790	SWP54451	500	LWP30469	500	[-1.32]	8250	3.10	2.0
HD 106304	9.069	SWP54443	500	(LWP30462)	500	[-1.34]	9750	3.50	2.0
HD 109995	7.630	SWP03932	n/a	LWP03637	504	[-1.72]	8500	3.10	3.0
HD 117880	9.064	SWP23442	X01	LWP03751	X02	[-1.64]	9300	3.30	2.0
HD 128801	8.738	SWP45161	500	LWP22291	502	[-1.45]	10300	3.55	2.0
HD 130095	8.128	SWP03921	n/a	LWR03505	n/a	[-1.87]	9000	3.30	2.0
HD 130201	10.110	SWP54449	500	LWP30466	500	[-1.00]	8650	3.50	2.0
HD 139961	8.860	SWP45165	400	LWP23523	502	[-1.71]	8500	3.20	3.0
HD 161817	6.976	SWP03923	n/a	LWR03506	n/a	[-1.55]	7550	3.00	3.0
HD 167105	8.966	SWP55803	500	LWP24147	501	[-1.56]	9050	3.30	3.0
HD 180903	9.568	SWP46057	402	LWP30467	400	[-1.45]	7700	3.10	3.0
HD 202759	9.09v	SWP46056	300	LWP24146	502	[-2.12]	7500	3.05	2.0
HD 213468	10.926	SWP10663	302	LWR09371	n/a	[-1.67]	9150	3.30	2.0
HD 252940	9.098	SWP56153	500	LWP24148	502	[-1.77]	7550	2.95	3.5
BD+00 145	10.580	SWP11203	502	LWR09819	n/a	[-2.45]	9700	4.00	2.0
BD+32 2188	10.756	SWP07852	502	LWP30459	500	[-1.11]	10450	2.10	1.0
BD+42 2309	10.771	SWP23441	407			[-1.63]	8800	3.20	2.0

Figure 1: Comparison of fluxes $F_{\lambda }$ computed from new-ODF models (full thick line) and old-ODF models (dashed line): a) for different $T_{\rm eff}$; b) for different $\log\,g$.

Figure 2: Comparison of fluxes $F_{\lambda }$ computed from new-ODF models (full thick line) and old-ODF models (dashed line) for different metallicities [M/H].