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Published March 1, 2016 | Accepted Version
Journal Article Open

Rapidly Rising Transients in the Supernova - Superluminous Supernova Gap

Abstract

We present observations of four rapidly rising (t_(rise) ≈ 10 days) transients with peak luminosities between those of supernovae (SNe) and superluminous SNe (M_(peak) ≈ −20)—one discovered and followed by the Palomar Transient Factory (PTF) and three by the Supernova Legacy Survey. The light curves resemble those of SN 2011kl, recently shown to be associated with an ultra-long-duration gamma-ray burst (GRB), though no GRB was seen to accompany our SNe. The rapid rise to a luminous peak places these events in a unique part of SN phase space, challenging standard SN emission mechanisms. Spectra of the PTF event formally classify it as an SN II due to broad Hαemission, but an unusual absorption feature, which can be interpreted as either high velocity Hα(though deeper than in previously known cases) or Si II (as seen in SNe Ia), is also observed. We find that existing models of white dwarf detonations, CSM interaction, shock breakout in a wind (or steeper CSM), and magnetar spin down cannot readily explain the observations. We consider the possibility that a "Type 1.5 SN" scenario could be the origin of our events. More detailed models for these kinds of transients and more constraining observations of future such events should help to better determine their nature.

Additional Information

© 2016 The American Astronomical Society. Received 2015 September 1; accepted 2016 January 14; published 2016 February 25. We thank J. Silverman and J. Johansson for helpful discussions and S. Sim and M. Kromer for sharing their white dwarf detonation models. This paper is based on observations obtained at the Cerro Paranal Observatory (ESO program 176.A-0589) and with the Samuel Oschin Telescope as part of the Palomar Transient Factory project. We are grateful for the assistance of the staffs at the various observatories where data were obtained. This work made use of the astronomy & astrophysics package for Matlab (Ofek 2014). Some of the work presented here is supported by the National Science Foundation under Grant No. 1313484. I.A. and A.G. acknowledge support by the Israeli Science Foundation and an EU/FP7/ERC grant. A.G. further acknowledges grants from the BSF, GIF, and Minerva, as well as the "Quantum universe" I-Core program of the planning and budgeting committee and the ISF, and a Kimmel Investigator award. The work of W.M.W. and L.B. was supported by the National Science Foundation under grants PHY 11-25915 and AST 11-09174. The Dark Cosmology Centre is funded by the Danish National Research Foundation. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Some data are based on observations obtained at the Gemini Observatory processed using the Gemini IRAF package, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministrio da Cincia, Tecnologia e Inovao (Brazil), and Ministerio de Ciencia, Tecnologa e Innovacin Productiva (Argentina). This work made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University.

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August 20, 2023
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October 20, 2023