Infrared photometry of HDE 226868 (Cyg X-1) from 2.3 to 10 MU : mass loss rate.

Abstract

Infrared photometry between 2.3 and 10 microns, shows an ionized gaseous envelope surrounding the supergiant OB star HDE 226868, the optical counterpart of the X-ray binary system Cyg X-1. The mean extent of the envelope at 10 microns is approximately 1.3 R (asterisk). The mass loss rate of HDE 226868 derived from 10 microns ff + bf emission flux, adopting a wind velocity law of the type described by Castor and Lamers (1979) with beta = 2, is 3.5 x 10 to the -6th solar masses/yr. This value of the mass loss rate is sufficient to account for the X-ray emission of Cyg X-1, under the assumption that the X-ray source is powered by accretion from a stellar wind.