High resolution H α spectroscopy of the bright RS CVn system HR 7275

HR 7275 is a bright, long-period (28 day), single-lined RS CVn binary. High-resolution (0.36 A) and good signal-to-noise ratio (S/N ∼ 150) echelle spectra do not show any clear evidence of the secondary in the system on spectral lines. Also, absence of a continuum on a low-resolution UV spectrum (IUE merged log) and the known mass function imply a main-sequence secondary with a spectral type late F to middle G, corresponding to the mass range of 0.9 < M2, 1.1 solar masses. This corresponds to a 1 < M1 < 1.5 solar masses mass range for the primary. The present spectra show variable Hα from the primary (K 1 III-IV). At least 30 per cent excess emission with respect to Arcturus and about 7 per cent modulation of the central intensity in the term of continuum at Hα has been measured. (author)