Do high-spin high mass X-ray binaries contribute to the population of merging binary black holes?

Abstract

Gravitational-wave observations of binary black hole (BBH) systems point to black hole spin magnitudes being relatively low. These measurements appear in tension with high spin measurements for high-mass X-ray binaries (HMXBs). We use grids of MESA simulations combined with the rapid population-synthesis code COSMIC to examine the origin of these two binary populations. It has been suggested that Case-A mass transfer while both stars are on the main sequence can form high-spin BHs in HMXBs. Assuming this formation channel, we show that depending on critical mass ratios for the stability of mass transfer, 48-100% of these Case-A HMXBs merge during the common-envelope phase and up to 42% result in binaries too wide to merge within a Hubble time. Both MESA and COSMIC show that high-spin HMXBs formed through Case-A mass transfer can only form merging BBHs within a small parameter space where mass transfer can lead to enough orbital shrinkage to merge within a Hubble time. We find that only up to 11% of these Case-A HMXBs result in BBH mergers, and at most 20% of BBH mergers came from Case-A HMXBs. Therefore, it is not surprising that these two spin distributions are observed to be different.

Tossing Black Hole Spin Axes

“…The rationale for allowing the possibility χ 1 → 1 is twofold: first, the estimated spins of BHs observed in HMXBs are apparently all quite large (Miller-Jones et al 2021) with values between 0.84 and 0.99; and, second, some of the most massive BH components (and thus in general expected to have formed first) in recorded BH+BH mergers seem to possess rather large values of χ 1 (Abbott et al 2022b, with the usual caveat that these measurements have large uncertainties in general). This evidence suggests that either (i) isolated binary evolution may produce larger spins of the first-born BHs than predicted from current theory, (ii) the BHs in these HMXBs and BH+BH merger sources could possibly have obtained their rapid spins from chemical homogeneous evolution (Mandel & de Mink 2016;Marchant et al 2016), or (iii) the general populations of (near-)Galactic HMXBs with rapid BH spins and BH+BH mergers are distinct (Gallegos-Garcia et al 2022). The rapidly spinning BHs in the former population may give support to the third possibility and could therefore conveniently alleviate the problem of aligning rapidly spinning BHs (see below), following a core collapse with spin-axis tossing.…”

Constraints on the contributions to the observed binary black hole population from individual evolutionary pathways in isolated binary evolution

“…However, it is worth nothing that there may still be additional channels that contribute to the formation of binary black holes that are not currently modelled within COMPAS, such as formation through stable mass transfer on the main sequence (so called case A mass transfer) (Valsecchi et al 2010;Qin et al 2019;Neijssel et al 2021), though we do not expect this to be the dominant channel (cf. Gallegos-Garcia et al 2022).…”