On the problem of detection of the circumstellar clouds from 2800 MgII observations

Abstract

A new method for the detection of the circumstellar clouds around the hot stars of O-B classes is developed. The method is based on the fact, connected with the large dispersion in the observed equivalent widths,W*(2800 MgII) of non-stellar origin, for a selected group of stars withE(B-V)=0. The separation of observed magnitudes ofW(2800) in two components ‘interstellar’Wi, and ‘circumstellar’Wc is realised. It is shown that the circumstellar clouds really existed around ≈90% of hot stars analysed in the present paper (total number of stars 46, Table II). In 30% cases of hot stars circumstellar clouds are very powerful (the radii are less than 1pc, the masses less than 1 solar mass). The usual model for interstellar medium seems to be unacceptable for the system ‘hot star+circumstellar cloud’.