Astron. Astrophys. 326, 1069-1075 (1997)

2. Observations

The globular cluster programme stars are listed in Table 1, together with the photometric parameters derived from the literature. The variables were chosen from the work of Sawyer (1955), and Sawyer Hogg (1973) (see column 7). Although the variable M56_V6 is almost certainly of RV Tau class, M2_V6 and M13_SH11 need further confirmation (see Demers (1969); Eggen (1986)). Companion red giants were selected from various references shown in column 7, and were chosen to be bright, not excessively red or crowded, and having, if possible, previous spectroscopy or accurate photometry reported in the literature.

Table 1. Photometric parameters of programme stars
¹ S55 = Sawyer (1955); S88 = Suntzeff et al. (1988); H75 = Harris (1975); SH73 = Sawyer Hogg (1973); Cudworth and Monet (1979); B = 65 Barbon (1965)

Observations were made in July 1993, with the Utrecht Echelle Spectrograph (UES) on the 4.3m William Herschel Telescope (WHT), at the Observatorio Roque de los Muchachos, La Palma. The resolution was around 50,000 with the Tek CCD, the wavelength coverage mostly complete from 4650 - 7160A (falling off towards the red end), and the signal to noise ratio (S/N) in the range 70 to 180. Several exposures of 1800 seconds were made of each star, to ensure good cosmic ray removal, and adequate S/N.

© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998
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