Polarization Signature of Companion-fed Supernovae Arising from BH–NS/BH Progenitor Systems

Abstract

The formation of black hole–neutron star (BH–NS) or BH–BH systems may be accompanied by special supernova (SN) signals, due to the accretion feedback from the companion BH. The additional heating, which is mainly attributed to the Blandford–Payne mechanism, would disrupt the isotropic nature of the luminosity distribution on the surface of the SN ejecta, leading to the appearance of polarization. Here we develop a three-dimensional Monte Carlo polarization simulation code to conduct simulations for these special SNe. We find that the maximum polarization level of ∼2% occurs at the peak time of SN emission in the “close-binary” scenario, while in the “faraway-binary” case maximum polarization (i.e., ∼0.7%) is observed at a considerably later time than the peak of the SN. The magnitude of polarization is dependent on the degree of unevenness in the luminosity distribution and the angle between the line of sight and the equatorial direction. When considering the geometric distortion of SN ejecta at the same time, the magnitude of polarization may either increase (for a oblate ellipsoidal shape) or decrease (for a prolate ellipsoidal shape). The polarization signatures represent a promising auxiliary instrument to facilitate the identification of the companion-fed SNe. Moreover, comparing the event rate of these special SNe with the event rate density of LIGO-Virgo-detected BH–NS/BH systems could further help to distinguish the BH–NS/BH formation channel.

Bumpy Superluminous Supernovae Powered by a Magnetar–Star Binary Engine

“…The effect of companions on SN lightcurves has already been discussed in the literature (e.g., Gao et al 2020;Soker 2020;Hirai & Podsiadlowski 2022;Wen et al 2023) and has been observed in SN 2022jli (Moore et al 2023;Chen et al 2024), identified as a normal Type Ic SN. In this Letter, we propose a magnetar-star binary engine model to explain bumpy SLSNe.…”