Accretion in massive colliding-wind binaries and the effect of the wind momentum ratio

We carry out a numerical experiment for ejecting winds in a massive colliding-wind binary system and quantify the accretion on to the secondary star under different primary mass-loss rates. We set a binary system comprising a luminous blue variable (LBV) as the primary and a Wolf-Rayet (WR) star as the secondary, and vary the mass-loss rate of the LBV to obtain different values of the wind momentum ratio eta. Our simulations include two sets of cases: one in which the stars are stationary; and one that includes the orbital motion. As eta decreases, the colliding-wind structure moves closer to the secondary. We find that for eta less than or similar to 0.05, the accretion threshold is reached and clumps that originate from instabilities are accreted on to the secondary. For each value of eta, we calculate the mass accretion rate and identify different regions in the (M)over dot(acc) - eta diagram. For 0.001 less than or similar to eta less than or similar to 0.05, the accretion is sub-Bondi-Hoyle-Lyttleton (BHL), and the average accretion rate satisfies the power law (M)over dot(acc) proportional to eta(-1.73) 0.05, for static stars. The accretion is not continuous but rather changes from sporadic to a larger duty cycle as eta decreases. For eta less than or similar to 0.001, the accretion becomes continuous in time, and the accretion rate is BHL, up to a factor of 0.4-0.8. The simulations that include the orbital motion give qualitatively similar results, with the steeper power law (M)over dot(acc) proportional to eta(-1.86) for the sub-BHL region and lower eta as an accretion threshold.

Automated summary

This study conducts a numerical experiment to investigate the wind ejection phenomenon in a massive colliding-wind binary system, and quantifies the accretion onto the secondary star based on different primary mass-loss rates. The results show that as the wind momentum ratio eta decreases, the colliding-wind structure moves closer to the secondary star. The study finds that when eta is less than or equal to 0.05, clumps originating from instabilities are accreted onto the secondary, reaching the accretion threshold. The mass accretion rate and different regions in the (M)over dot(acc) - eta diagram are calculated for each eta value.