The distances to the X-ray binaries LSI +61° 303 and A0535+262

Abstract

Chevalier & Ilovaisky use Hipparcos data to show that the X-ray binary systems LSI+61° 303 and A0535+262 are a factor of 10 closer (i.e. d ≃ few hundred pc) than previously thought (d ≃ 2 kpc). We present high-quality CCD spectra of the systems, and conclude that the spectral types, reddening and absolute magnitudes of these objects are strongly inconsistent with the closer distances. We propose that the Hipparcos distances to these two systems are incorrect owing to their relatively faint optical magnitudes.