Fast Rotating Low-mass Stars from Post Mass-transfer and Post Wind Mass-transfer Binary Systems

More than half of stars are in a binary system. When the two stars are close, the donor star could transfer mass onto the accretor star through the inner Lagrangian point, where the Roche-lobe of the two stars meets. Other than mass, angular momentum is transferred which can spin-up the rotation of the accretor star. In a recent work of long-term spectroscopy binary survey, several fast rotating post mass-transfer stars in young open clusters have been found. In this work, we use the infrastructure functionality in POpulation SYnthesis with Detailed binary-evolution simulatiONs (POSYDON, the next generation binary population synthesis code based on the MESA detailed binary evolutionary simulations), to establish a big low-mass binary grid focusing on the rotation of the accretor star. State-of-the-art magnetic braking presciptions are implemented to explain the data and the possible assistance in stellar gyrochronology in telling the age of those systems. In addition, we find that accretion through wind mass-transfer or even a small amount of mass through regular mass-transfer can account for the fast rotation measurements.

MS acknowledges support through the GBMF8477 Grant (PI Kalogera).