Pulsational Pair-instability Supernovae in Very Close Binaries

Abstract

Pair-instability and pulsational pair-instability supernovae (PPISN) have not been unambiguously observed so far. They are, however, promising candidates for the progenitors of the heaviest binary black hole (BBH) mergers detected. If these BBHs are the product of binary evolution, then PPISNe could occur in very close binaries. Motivated by this, we discuss the implications of a PPISN happening with a close binary companion, and what impact these explosions have on the formation of merging BBHs through binary evolution. For this, we have computed a set of models of metal-poor (Z /10) helium stars using the MESA software instrument. For PPISN progenitors with pre-explosion masses > 50M we find that, after a pulse, heat deposited throughout the layers of the star that remain bound cause it to expand to more than 100R for periods of 10 2 − 10 4 yrs depending on the mass of the progenitor. This results in long-lived phases of Roche-lobe overflow or even common-envelope events if there is a close binary companion, leading to additional electromagnetic transients associated to PPISN eruptions. If we ignore the effect of these interactions, we find that mass loss from PPISNe reduces the final black hole spin by ∼ 30%, induces eccentricities that can be detected by the LISA observatory, and can produce a double-peaked distribution of measured chirp masses in BBH mergers observed by ground-based detectors.

GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs

“…Even with the set of ten BBH and one BNS, several outstanding questions remain regarding the origin and evolution of the detected binaries. To date, no binary components have been observed in either of the two putative mass gaps [139,140]-one between NSs and BHs and the other one due to pair instability supernovae [136,219]. Gravitational-wave measurement of BH spins favors either small magnitudes or large misalignment with the orbital angular momentum.…”

Mind the Gap: The Location of the Lower Edge of the Pair-instability Supernova Black Hole Mass Gap

“…Input files necessary to reproduce this work and the resulting output files are made freely available at www.mesastar.org. 8 Based on the results of Marchant et al (2019), we evolve systems around the lower edge of the PISN BH mass gap, with initial helium core masses between 30 and 105 M  . We chose to evolve bare helium cores because stars in this mass range are expected to lose their hydrogen-rich envelope long before their death.…”

“…This removes between a few tenths and a few tens of solar masses of material in a pulsational mass loss episode (PPI) (Yoshida et al 2016;Marchant et al 2019;Woosley 2019). Some stars will undergo "weak" pulsations; these stars undergo PPI instabilities but do not drive a shock sufficient to remove mass (Woosley 2017;Marchant et al 2019). To focus on the impact that this process has on the BH masses, in this study we define only systems that can drive mass loss as undergoing a pulse.…”

Sensitivity of the lower edge of the pair-instability black hole mass gap to the treatment of time-dependent convection

“…Several authors have noted that the amount of mass lost is sensitive to the treatment of convection, both before and during the pulses (e.g., Woosley 2017;Marchant et al 2019;Leung et al 2019). Here, we compare two grids of massive bare He core models to highlight the differences resulting from variations in the treatment of time-dependent convection.…”

“…Stars that develop helium (He) core masses exceeding M He 30 M are predicted to encounter the PPI and shed significant amounts of mass in subsequent pulsation episodes (e.g., Rakavy & Shaviv 1967;Yoshida et al 2016;Woosley 2017;Takahashi 2018;Marchant et al 2019;Leung et al 2019;Woosley 2019). The amount of mass lost in these pulses, together with the previous wind mass loss, determines the mass distribution of BHs formed.…”