2 Program stars and observations

We have been able to secure spectrograms of a total of 8 blue-straggler candidates at two different observatories (Kitt Peak National Observatory - KPNO, and Calar Alto Observatory - CA). Some essential information about our targets and details of their observation are given in Table 1. Additional information about the stars listed in the table can be also found in the WEBDA data base (Mermilliod 1999). The well investigated star $\alpha$ Lyr (Vega) has been chosen as a reference star in order to control our method of the analysis.

   

Table 1: Data for program stars

K	GET	V	B-V	MP	Region,Å	Instrument
K88	2873	13.10	0.38	0.98	4220-4525	KPNO
K316	5569	13.79	0.36	0.98	4220-4525	KPNO
K371	5951	12.95	0.36	0.98	4220-4525	KPNO
					H$\gamma$, H$\beta$	CA
K409	6268	12.98	0.31	0.53	4220-4525	KPNO
					H$\gamma$	CA
K677	8404	11.16	0.16	0.53	4220-4525	KPNO
					4450-4585, H$\beta$	CA
K746	8804	12.74	0.39	0.98	4220-4525	KPNO
					H$\gamma$	CA
K1211	13273	11.55	0.18	0.97	H$\gamma$, H$\beta$	CA
					4450-4580	CA
K1270	14054	13.46	0.46	0.98	4220-4525	KPNO
Vega		0.06			4220-4525	KPNO
K - Küstner (1923) number; GET - Gim et al. (1998a) number; MP - membership probability
as determined by McNamara & Solomon (1981).

KPNO spectra were obtained during October 1-3, 1985, with the 4-m telescope equipped with an echelle spectrograph and CCD camera (resolution 0.12 Å/px, S/N ratio varying from approximately 30 to 80 at the continuum level, except for Vega). These spectrograms were extracted from the frames in the usual manner by using the IRAF package. All spectra consisted of nine (not overlapping) orders, each covering approximately 30 Å. Because of the small sizes of the observed bands we met some problems with the correct continuum placement in the vicinity of the H$\gamma$ line. To avoid the problems that could be caused by the wrong continuum placement, the two adjacent orders from the spectrum of each star ranging from 4320 Å  to 4390 Å  were discarded in the further analysis.

The CA spectral material was obtained during two runs in January and September 1986 with the 2.2-m telescope equipped with a Coudé spectrograph (resolution 0.26 Å/px, S/N ratio about 40-70). These observations were aimed at getting reliable profiles of the hydrogen lines H$\gamma$ and H$\beta$. The spectral regions cover approximately 130 Å  each.

The final spectra were treated using the DECH20 spectra processing package (Galazutdinov 1992).