학술논문
SN2017egm: A Helium-rich Superluminous Supernova with Multiple Bumps in the Light Curves
Document Type
Working Paper
Author
Zhu, Jiazheng; Jiang, Ning; Dong, Subo; Filippenko, Alexei V.; Rudy, Richard J.; Pastorello, A.; Ashall, Christopher; Bose, Subhash; Post, R. S.; Bersier, D.; Benetti, Stefano; Brink, Thomas G.; Chen, Ping; Dou, Liming; Elias-Rosa, N.; Lundqvist, Peter; Mattila, Seppo; Russell, Ray W.; Sitko, Michael L.; Somero, Auni; Stritzinger, M. D.; Wang, Tinggui; Brown, Peter J.; Cappellaro, E.; Fraser, Morgan; Kankare, Erkki; Moran, S.; Prentice, Simon; Pursimo, Tapio; Reynolds, T. M.; Zheng, WeiKang
Source
Subject
Language
Abstract
When discovered, SN~2017egm was the closest (redshift $z=0.03$) hydrogen-poor superluminous supernova (SLSN-I) and a rare case that exploded in a massive and metal-rich galaxy. Thus, it has since been extensively observed and studied. We report spectroscopic data showing strong emission at around He~I $\lambda$10,830 and four He~I absorption lines in the optical. Consequently, we classify SN~2017egm as a member of an emerging population of helium-rich SLSNe-I (i.e., SLSNe-Ib). We also present our late-time photometric observations. By combining them with archival data, we analyze high-cadence ultra-violet, optical, and near-infrared light curves spanning from early pre-peak ($\sim -20\,d$) to late phases ($\sim +300\,d$). We obtain its most complete bolometric light curve, in which multiple bumps are identified. None of the previously proposed models can satisfactorily explain all main light-curve features, while multiple interactions between the ejecta and circumstellar material (CSM) may explain the undulating features. The prominent infrared excess with a blackbody luminosity of $10^7$--$10^8\,L_{sun}$ detected in SN~2017egm could originate from the emission of either an echo of a pre-existing dust shell, or newly-formed dust, offering an additional piece of evidence supporting the ejecta-CSM interaction model. Moreover, our analysis of deep $Chandra$ observations yields the tightest-ever constraint on the X-ray emission of an SLSN-I, amounting to an X-ray-to-optical luminosity ratio $\lesssim 10^{-3}$ at late phases ($\sim100-200\,d$), which could help explore its close environment and central engine.
Comment: 25 pages, 14 Figures, 4 Tables; accepted for publication in ApJ (Mar. 2023)
Comment: 25 pages, 14 Figures, 4 Tables; accepted for publication in ApJ (Mar. 2023)