Wind Accretion in Massive Binaries Experiencing High Mass Loss Rates: II. Eccentricity

Abstract

We perform numerical simulations to investigate high-power wind accretion in massive binary systems undergoing enhanced mass-loss episodes. The primary star is taken in the mass range $M_{1} = 60$--$90\,\mathrm{M_{\odot}}$, while the companion is a $30\,\mathrm{M_{\odot}}$ hot star. We model binary orbits with eccentricities of $e = 0$--$0.6$ and orbital periods of $P=455$--$1155$ days. We initiate strong eruptive events for the primary with mass-loss rates of $\dot{M}_{\rm w} = 10^{-2}$ -- $10^{-1}\,\rm{M_{\odot}~{yr}^{-1}}$, lasting for $1.5$ years. A fraction of the ejected wind material is accreted by the companion, with the accretion efficiency determined by the orbital separation, eccentricity, and stellar mass ratio. We analyze the resulting accretion rates and provide an analytical relation describing their dependence on the stellar mass ratio, mass-loss rate, and orbital parameters. We find that although the accretion modifies the stellar parameters of the secondary, the companion remains in thermal equilibrium and does not undergo significant radial expansion. We further include wind mass loss from the companion during wind accretion and find a substantial reduction in accretion efficiency compared to no wind scenario. For longer orbital periods, the models yield negative accretion rates, implying that any captured material is expelled or prevented from settling onto the accretor. These results provide new insight into the role of eccentric orbits and extreme mass-loss events in shaping the mass-transfer processes in massive binaries.

Figures (4)

• Figure 1: Multi-panel visualisation of the stellar parameters listed in Table \ref{['T1']} as a function of primary mass $M_1$ at the onset of wind accretion. The panels show stellar mass, effective temperature, radius, surface gravity, luminosity, and wind mass-loss rate. The figure highlights the systematic trends of the primary star properties across the $60$–$100~\rm M_\odot$ models.
• Figure 2: Accreted mass $\Delta M$ (panel a) and corresponding mass accretion rate $\dot{M}_{\rm acc}$ (panel b) as a function of orbital period for the $100$--$30~\rm M_\odot$ binary system at $e=0$.
• Figure 3: Here panel (a) shows the mass accretion rate, $\dot{M}_{\rm acc}$, as a function of orbital period for the $100$-$30~\rm M_\odot$ binary system, shown for different orbital eccentricities ($e = 0.0, 0.2, 0.4, 0.6$). The accretion rates are plotted in units of $10^{-6}\,\mathrm{M_\odot}\,\mathrm{yr}^{-1}$. Panel (b) shows the three-dimensional representation of $\dot{M}_{\rm acc}$ as a function of orbital period and eccentricity, illustrating the combined dependence of the wind-accretion efficiency on orbital separation and orbital eccentricity.
• Figure 4: Mass accretion rates $\dot{M}_{\rm acc}$ as a function of orbital period for different binary systems at $e=0$. Each panel corresponds to a different primary mass. The red and blue points show the cases with mass loss rates of $10^{-1}$ and $10^{-2}~\rm M_\odot~\mathrm{yr}^{-1}$, respectively.