2021MNRAS.505.2170T -
Mon. Not. R. Astron. Soc., 505, 2170-2176 (2021/August-1)
Population III binary black holes: effects of convective overshooting on formation of GW190521.
TANIKAWA A., KINUGAWA T., YOSHIDA T., HIJIKAWA K. and UMEDA H.
Abstract (from CDS):
GW190521 is a merger of two black holes (BHs), wherein at least one BH lies within the pair-instability (PI) mass gap, and it is difficult to form because of the effects of PI supernovae and pulsational PI (PPI). In this study, we examined the formation of GW190521-like BH-BHs under Population (Pop) III environments by binary population synthesis calculations. We reveal that convective overshooting in stellar evolution strongly affects the formation of GW190521-like BH-BHs. A model with a small overshoot parameter (similar to GENEC) can form GW190521-like BH-BHs. The derived merger rate is 4 x 10–2 yr–1 Gpc–3 at a redshift of ∼0.82, which is comparable to the merger rate of GW190521-like BH-BHs inferred by gravitational wave (GW) observations. In this model, a ∼90 M☉ star collapses to form a ∼90 M☉ BH by avoiding PPI and PISN even if it is a member of a binary star. This is because it expands up to 102 R☉, and lose only little mass through binary evolution. However, a model with a large overshoot parameter (similar to Stern) cannot form GW190521-like BH-BHs at all. Thus, we cannot conclude that a Pop III binary system is the origin of GW190521 because determination of the overshoot parameter involves highly uncertain. If a Pop III binary system is the origin of GW190521, the merger rate of BH-BHs including a 100-135 M☉ BH is substantially smaller than that of GW190521-like BH-BHs. This will be assessed by GW observations in the near future.
Abstract Copyright:
© 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society
Journal keyword(s):
gravitational waves - binaries: close - stars: black holes - stars: Population III - black hole mergers
Simbad objects:
4
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