Constraining the mass transfer in massive binaries through progenitor evolution models of Wolf-Rayet+O binaries

Abstract

Abstract. Since close WR+O binaries are the result of a strong interaction of both stars in massive close binary systems, they can be used to constrain the highly uncertain mass and angular momentum budget during the major mass transfer phase. We explore the progenitor evolution of the three best suited WR+O binaries HD 90657, HD 186943 and HD 211853, which are characterized by a WR/O mass ratio of ∼0.5 and periods of 6...10 days. We are doing so at three different levels of approximation: predicting the massive binary evolution through simple mass loss and angular momentum loss estimates, through full binary evolution models with parametrized mass transfer efficiency, and through binary evolution models including rotation of both components and a physical model which allows to compute mass and angular momentum loss from the binary system as function of time during the mass transfer process. All three methods give consistently the same answers. Our results show that, if these systems formed through stable mass transfer, their initial periods were smaller than their current ones, which implies that mass transfer has started during the core hydrogen burning phase of the initially more massive star. Furthermore, the mass transfer in all three cases must have been highly non-conservative, with on average only ∼10% of the transferred mass being retained by the mass receiving star. This result gives support to our system mass and angular momentum loss model, which predicts that, in the considered systems, about 90% of the overflowing matter is expelled by the rapid rotation of the mass receiver close to the Ω-limit, which is reached through the accretion of the remaining 10%.

Binary star progenitors of long gamma-ray bursts

“…The finding of Hammer et al (2006), that the nearest three long gammaray bursts may be due to runaway stars is in remarkable agreement with our scenario. While the collapsar progenitor in our binary model travels only 200 pc before it dies, compared to the 400...800 pc deduced by Hammer et al (2006), binary evolution resulting in higher runaway velocities are certainly possible (Petrovic et al 2005a). It remains to be analyzed whether the runaway scenario is compatible with the finding that long GRBs are more concentrated in the brightest regions of their host galaxies than core collapse supernovae (Fruchter et al 2006).…”

“…We chose an early Case B system with an initial mass ratio close to one for two reasons. Firstly, the expected mass transfer efficiency for this case was about 60% (meaning that 60% of the transfered matter can be retained by the mass gainer), based on the calculations by , Langer et al (2004), and Petrovic et al (2005a). Secondly, a Case B rather than Case A system was chosen to avoid synchronization after the major mass transfer phase.…”

“…It includes tidal coupling, mass and angular momentum transfer, and thermohaline mixing. The mass transfer efficiency is determined by the angular momentum balance of the accreting star: the amount of accreted matter is limited by the constraint that the angular momentum which it carries does not drive the rotation of the star beyond critical rotation (Petrovic et al 2005a). To determine the accreted angular momentum, the code solves the equation of motion of test particles leaving the mass donor into a Roche potential (cf.…”

Fundamental parameters of the close interacting binary HD 170582 and its luminous accretion disc

“…If critical velocity is rapidly reached, as suggested by Packet (1981) andde Mink et al (2007), then the disc could turn to be relatively massive, due to the inadequacy of the gainer of accreting more material. This last point has been debated; Petrovic et al (2005) assume that accretion ceases when the mass gaining star reaches Keplerian rotation. On the contrary, Popham & Narayan (1991) argue that a star near critical rotation can sustain accretion due to viscous coupling between the star and the disc.…”

Massive binaries and the enrichment of the interstellar medium in globular clusters

“…In principle, tides can counteract the effect of spin-up through mass transfer in close binaries. Petrovic et al (2005) computed detailed binary evolution models, taking into account these effects. They find that massive binaries with initial periods as short as 3-6 days lose 70-80% of the transferred mass, on average.…”