Extreme Supernova Models for the Super-luminous Transient ASASSN-15lh

Chatzopoulos, E. and Wheeler, J. C. and Vinkó, József and Nagy, Andrea and Wiggins, B. K. (2016) Extreme Supernova Models for the Super-luminous Transient ASASSN-15lh. ASTROPHYSICAL JOURNAL, 828 (2). ISSN 1538-4357

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Abstract

SUBMITTED TO APJ ON 2016 MARCH 22 Preprint typeset using LATEX style emulateapj v. 01/23/15 EXTREME SUPERNOVA MODELS FOR THE SUPERLUMINOUS TRANSIENT ASASSN–15lh E. CHATZOPOULOS1, 7 , J. C. WHEELER2 , J. VINKO 2, 3, 4 , A. P. NAGY 3 , B. K. WIGGINS 5, 6 , AND W. P. EVEN 5 1Department of Astronomy & Astrophysics, Flash Center for Computational Science, University of Chicago, Chicago, IL, 60637, USA 2Department of Astronomy, University of Texas at Austin, Austin, TX, 78712, USA 3Department of Optics and Quantum Electronics, University of Szeged, D´om t´er 9, Szeged, 6720 Hungary 4Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, P.O. Box 67, H–1525, Budapest, Hungary 5Center for Theoretical Astrophysics/CCS–2, Los Alamos National Laboratory, Los Alamos, NM, 87544, USA 6Brigham Young University, Department of Physics and Astronomy, Provo, UT, 84602, USA Submitted to ApJ on 2016 March 22 ABSTRACT The recent discovery of the unprecedentedly superluminous transient ASASSN–15lh (or SN 2015L) with its UV–bright secondary peak challenges all the power–input models that have been proposed for superluminous supernovae. Here we examine some of the few viable interpretations of ASASSN–15lh in the context of a stel- lar explosion, involving combinations of one or more power inputs. We model the lightcurve of ASASSN–15lh with a hybrid model that includes contributions from magnetar spin–down energy and hydrogen–poor circum- stellar interaction. We also investigate models of pure circumstellar interaction with a massive hydrogen– deficient shell and discuss the lack of interaction features in the observed spectra. We find that, as a supernova ASASSN–15lh can be best modeled by the energetic core–collapse of a ∼ 40 M star interacting with a hydrogen–poor shell of ∼ 20 M . The circumstellar shell and progenitor mass are consistent with a rapidly rotating pulsational pair–instability supernova progenitor as required for strong interaction following the final supernova explosion. Additional energy injection by a magnetar with initial period of 1–2 ms and magnetic field of 0.1−1×1014 G may supply the excess luminosity required to overcome the deficit in single–component models, but this requires more fine–tuning and extreme parameters for the magnetar, as well as the assumption of efficient conversion of magnetar energy into radiation. We thus favor a single–input model where the reverse shock formed in a strong SN ejecta – CSM interaction following a very powerful core–collapse SN explosion can supply the luminosity needed to reproduce the late–time UV–bright plateau.

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