Wolf-Rayet binaries: Evolutionary causes for their distribution in the Galaxy

Massive close binaries: Observations and evolutionary computations

“…Table II candidate of a black hole; the same holds for the system HD 97950 (f(M) = 0.15). The average height above the galactic plane for the sample = 280 pv which is much larger than the value holding for WR + OB binaries (i.e., 90 pc, Hidayat et al, 1984) and for OB-type stars (Gies and Bolton, 1986). Using this value for the mass of the CC of the suspected binaries listed in Table II and assuming an average inclination angle = 57.3 ~ (thus assuming that the orbits are randomly oriented in space), the table also gives the masses of the WR star in these systems.…”

“…Using the evolutionary computations of single stars of Maeder and Meynet (1987) and the average Mvi S -Tefr-spectral type-luminosity class calibration of TABLE I The actual mass of a star given its spectral type and luminosity class using the evolutionary tracks with CCO1; the numbers between brackets correspond to evolutionary tracks without CCO (Vanbeveren, 1987) Humphreys and McElroy (1984), Table I gives an average mass-spectral type-luminosity class relation for massive single stars and MCB components. The sample contains at least 4 binaries where observational evidence is present that mass transfer is going on, i.e., AO Cas (a contact system, Hilditch and Bell, 1987), 29 CMa (a semi-detached system with gas streams present, McCluskey et al, 1975), HD 149404 (the most evolved star, an O9Ia, is the less massive component, Massey and14 Cep (Hilditch, 1974). As a general rule it can be stated that non-evolved massive O-type binary components correspond to stars with initial ZAMS mass larger than 20 Mo, whereas the lower mass MCB components correspond to spectral type B0-B2 (V, IV, and III).…”

Wolf-Rayet Binaries: Evolutionary Causes for their Distribution in the Galaxy

“…In our Galaxy, 159 Population I Wolf-Rayet stars are known (van der Hucht et al, 1981;Hidayat et al, 1984). Table I gives the distribution between single WR stars, single WR stars with intrinsic absorption lines, double-line spectroscopic binaries, and single-line spectroscopic binaries.…”

“…In these tables the absolute visual magnitude M v , the heliocentric distance d, the galactocentric distance r, and the separation from the galactic plane z are from Hidayat et al (1984) and based on the intrinsic parameters given in II).…”

“…Thanks to the work of , Hidayat et al (1984) could use improved intrinsic parameters and new colours and spectral types for many of the fainter stars, in order to reinvestigate the galactic distribution of Population I Wolf-Rayet stars. In the present paper emphasis is put on the binaries versus the single stars.…”