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We study the impact of stellar cooling due to light axion emission on the formation and evolution of black hole binaries, via stable mass transfer and the common envelope scenario.~We find that in the presence of light axion emission, no binary black hole mergers are formed with black holes in the lower mass gap ($$M_{\rm BH} < 4 {\rm M}_\odot $$) via the common envelope formation channel.~In some systems, this happens because axions prevent Roche lobe overflow.~In others, they prevent the common envelope from being ejected.~Our results apply to axions with couplings $$ g_{a \gamma} \gtrsim 10^{-10}\, \rm GeV^{-1}$$ (to photons) or $$\alpha_{ae} \gtrsim 10^{-26} $$ (to electrons) and masses $$ m_a \ll 10 \, \rm keV$$.~Light, weakly coupled particles may therefore apparently produce a mass gap $$2 {\rm M}_\odot < M_{\rm BH} < 4 {\rm M}_\odot$$ in the LIGO/Virgo/KAGRA data, when no mass gap is present in the stellar remnant population.
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Numerical relativity simulations of the neutron star merger GW190425: microphysics and mass ratio effects
ABSTRACT GW190425 was the second gravitational wave (GW) signal compatible with a binary neutron star (BNS) merger detected by the Advanced LIGO and Advanced Virgo detectors. Since no electromagnetic counterpart was identified, whether the associated kilonova was too dim or the localization area too broad is still an open question. We simulate 28 BNS mergers with the chirp mass of GW190425 and mass ratio 1 ≤ q ≤ 1.67, using numerical-relativity simulations with finite-temperature, composition dependent equations of state (EOS) and neutrino radiation. The energy emitted in GWs is $$\lesssim 0.083\mathrm{\, M_\odot }c^2$$ with peak luminosity of 1.1–$$2.4\times ~10^{58}/(1+q)^2\, {\rm {erg \, s^{-1}}}$$. Dynamical ejecta and disc mass range between 5 × 10−6–10−3 and 10−5–$$0.1 \mathrm{\, M_\odot }$$, respectively. Asymmetric mergers, especially with stiff EOSs, unbind more matter and form heavier discs compared to equal mass binaries. The angular momentum of the disc is 8–$$10\mathrm{\, M_\odot }~GM_{\rm {disc}}/c$$ over three orders of magnitude in Mdisc. While the nucleosynthesis shows no peculiarity, the simulated kilonovae are relatively dim compared with GW170817. For distances compatible with GW190425, AB magnitudes are always dimmer than ∼20 mag for the B, r, and K bands, with brighter kilonovae associated to more asymmetric binaries and stiffer EOSs. We suggest that, even assuming a good coverage of GW190425’s sky location, the kilonova could hardly have been detected by present wide-field surveys and no firm constraints on the binary parameters or EOS can be argued from the lack of the detection.
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- Award ID(s):
- 2116686
- PAR ID:
- 10372058
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 516
- Issue:
- 4
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- p. 4760-4781
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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