Preprint

A Superluminous Supernova Lightened by Collisions with Pulsational Pair-instability Shells

Weili LinPhysics Department and Tsinghua Center for Astrophysics (THCA) , Tsinghua University , Beijing 100084 , ChinaXiaofeng WangYan LinCaltech Optical Observatories , California Institute of Technology , Pasadena , CA 91125 , USAA. Gal‐YamDepartment of Particle Physics and Astrophysics , Weizmann Institute of Science , 234 Herzl St. , 76100 Rehovot , IsraelJun MoPhysics Department and Tsinghua Center for Astrophysics (THCA) , Tsinghua University , Beijing 100084 , ChinaThomas G. BrinkDepartment of Astronomy , University of California , Berkeley , CA 94720-3411 , USAA. V. FilippenkoDepartment of Astronomy , University of California , Berkeley , CA 94720-3411 , USADanfeng XiangPhysics Department and Tsinghua Center for Astrophysics (THCA) , Tsinghua University , Beijing 100084 , ChinaR. LunnanWeiKang ZhengDepartment of Astronomy , University of California , Berkeley , CA 94720-3411 , USAPeter BrownDepartment of Physics and Astronomy , Texas A&M University , 4242 TAMU , College Station , TX 77843 , USAM. M. KasliwalDivision of Physics, Mathematics, and Astronomy , California Institute of Technology , Pasadena , CA 91125 , USAC. FremlingDivision of Physics, Mathematics, and Astronomy , California Institute of Technology , Pasadena , CA 91125 , USAN. BlagorodnovaD. O. MirzaqulovUlugh Beg Astronomical InstituteSh. A. EhgamberdievNational University of UzbekistanHan LinKaicheng ZhangPhysics Department and Tsinghua Center for Astrophysics (THCA) , Tsinghua University , Beijing 100084 , ChinaJicheng ZhangDepartment of Astronomy , Beijing Normal University , Beijing , People's Republic of ChinaShengyu YanPhysics Department and Tsinghua Center for Astrophysics (THCA) , Tsinghua University , Beijing 100084 , ChinaJujia ZhangDepartment of Astronomy , Beijing Normal University , Beijing , People's Republic of ChinaZhihao ChenDepartment of Astronomy , Stockholm University , AlbaNova , SE-106 91 Stockholm , SwedenLicai DengKun WangDepartment of Astronomy , China West Normal University , Nanchong , ChinaLin XiaoLingjun WangAstroparticle Physics , Institute of High Energy Physics , Chinese Academy of Sciences , Beijing 100049 , China

2023en

ABI

Annotatsiya

Superluminous supernovae are among the most energetic stellar explosions in the Universe, but their energy sources remain an open question. Here we present long-term observations of one of the closest examples of the hydrogen-poor subclass (SLSNe-I), SN~2017egm, revealing the most complicated known luminosity evolution of SLSNe-I. Three distinct post-peak bumps were recorded in its light curve collected at about $100$--350\,days after maximum brightness, challenging current popular power models such as magnetar, fallback accretion, and interaction between ejecta and a circumstellar shell. However, the complex light curve can be well modelled by successive interactions with multiple circumstellar shells with a total mass of about $6.8$--7.7\,M$_\odot$. In this scenario, large energy deposition from interaction-induced reverse shocks results in ionization of neutral oxygen in the supernova ejecta and hence a much lower nebular-phase line ratio of [O\,\textsc{i}] $\lambda6300$/([Ca\,\textsc{ii}] + [O\,\textsc{ii}]) $\lambda7300$ ($\sim 0.2$) compared with that derived for other superluminous and normal stripped-envelope SNe. The pre-existing multiple shells indicate that the progenitor of SN~2017egm experienced pulsational mass ejections triggered by pair instability within 2 years before explosion, in robust agreement with theoretical predictions for a pre-pulsation helium-core mass of 48--51\,M$_{\odot}$. Finally, this work shows that the final explosion product may be a black hole with about 40\,M$_{\odot}$, and has significant implication for the formation of such heavy black holes that have been recently observed by LIGO-Virgo gravitational wave detectors.

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DOI: 10.48550/arxiv.2304.10416

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