Detailed Simulations of Massive Hierarchical Triple Star Systems - Exploring the impact of the stellar physics on the evolutionary pathways of massive hierarchical triple systems

Abstract

Recent observations estimate that 30% of early B and O-type stars are found in triple systems. So far, the evolution of triple star systems has mainly been modeled using fast stellar codes. Their accuracy decreases with increasing mass, limiting their reliability for predicting the evolutionary pathways of massive triple systems. We coupled Tres, which by default uses Seba (fast stellar code) to Mesa to perform the first simulations of triple systems that combine a triple secular evolutionary code with a detailed, on-the-fly stellar code. After examining the differences between the stellar evolution predicted by the two codes, we simulate the evolution of a set of triple systems and compare their predicted evolutionary pathways. The predicted stellar tracks become increasingly divergent with increasing mass and wind mass loss efficiency. The maximal radial extent, crucial for determining whether the components of the triple systems interact, differ by up to two orders of magnitude between the two stellar codes in the considered mass range. This leads to divergences in the triples evolutionary pathways predicted by mesa and seba. Using mesa instead of seba, the minimum period for avoiding inner mass transfer is reduced by three orders of magnitude. This has important consequences for the formation of GW sources through the triple compact object channel. Our simulations offer new insights into the physics of triple systems, as key processes (mass loss, radial expansion, precession) are treated self-consistently. They indicate that the results of triple systems population synthesis studies must be interpreted cautiously, in particular when the considered masses are outside the range of the grid the fast codes are based on and when significant stellar winds are considered.