2024/11/04 by Emilio Tejeda, Tejeda, Emilio, J. A. Toalá +1 · 4 citations
Physics and Astronomy · #High-Energy Particle Collisions Research #Quantum Chromodynamics and Particle Interactions
paper · pdf · doi:10.48550/arxiv.2411.01755
The Bondi-Hoyle-Lyttleton (BHL) accretion model is widely used to describe how a compact object accretes material from a companion's stellar wind in binary systems. However, its standard implementation becomes inaccurate when the wind velocity (vw) is comparable to or less than the orbital velocity (vo), predicting non-physical accretion efficiencies above unity. This limits its applicability to systems with low wind-to-orbital velocity ratios (w= vw / vo ≤ 1), such as symbiotic systems. We revisit the implementation of the BHL model and introduce a geometric correction factor that accounts for the varying orientation of the accretion cylinder relative to the wind direction. This correction ensures physically plausible accretion efficiencies (η≤ 1) for all w in circular orbits. Our new implementation naturally predicts the flattening of the accretion efficiency observed in numerical simulations for w < 1, without the need for ad hoc adjustments. We also peer into the implications of our prescription for the less-explored case of eccentric orbits, highlighting the key role of the geometric correction factor in shaping the accretion process. We compare our predictions with numerical simulations, finding good agreement for a wide range of parameters. Applications to the symbiotic star R~Aqr and the X-ray binary LS 5039 are presented. This improved implementation offers a more accurate description of wind accretion in binary systems, with implications for stellar evolution, population synthesis, and observational data interpretation.