Stellar wind collision and X-ray generation in massive binaries

Accretion by the Secondary in η Carinae During the Spectroscopic Event. I. Flow Parameters

“…The X-ray emission results from the collision of the two winds from the two stars (Corcoran et al 2001a;Pittard & Corcoran 2002), as in similar massive binary systems (Usov 1992), most prominently, the WR-O binary system WR 140 ( Williams et al 1990). In the interacting massive binary system WR 140, the X-ray minimum is not flat, and it can easily be explained by absorption of the X-ray emission by the dense wind of the WR star (Corcoran et al 2004a;Pollock et al 2005).…”

“…In this type of wind interaction, the secondary's luminosity slows down the primary's wind before it encounters the shock wave (Gayley et al 1997), substantially reducing the X-ray intensity and making it softer (Usov 1992). The slowing down process by the secondary radiation pressure affects the location of the new stagnation point, but does not push it back to its original place.…”

“…( Near periastron and for these parameters the post shock electron density is $10 10 cm À3 and the temperature is $10 8 K; the equalization time of ion and electron temperature for these values is $0.1 day [Usov 1992], shorter than the cooling time.) The fraction of the shocked wind that cools to very low temperatures and is compressed is (eq.…”

“…Following Usov (1992), we take the wind with the larger momentum flux, in our case the primary's wind, to be plane parallel near the secondary star. Because of the orbital motion, the stagnation point of the secondary's wind will be ahead of the line joining the centers of the two stars (Fig.…”

“…However, near periastron when the stagnation distance D g2 becomes small, the cooling of gas very close to the stagnation point becomes nonnegligible because very close to the stagnation point Cow2 3 f 2 ( Usov 1991). The secondary's wind is shocked to a temperature of $10 8 K, where the cooling function dependence on temperature is à ¼ à 0 T 0:4 .…”