Light Curves of Hydrogen-poor Superluminous Supernovae from the Palomar Transient Factory

Creators: De Cia, Annalisa; Yan, Lin; Kasliwal, M. M.

Abstract

We investigate the light-curve properties of a sample of 26 spectroscopically confirmed hydrogen-poor superluminous supernovae (SLSNe-I) in the Palomar Transient Factory survey. These events are brighter than SNe Ib/c and SNe Ic-BL, on average, by about 4 and 2 mag, respectively. The peak absolute magnitudes of SLSNe-I in rest-frame g band span −22 ≾ M g ≾ −20 mag, and these peaks are not powered by radioactive ^(56)Ni, unless strong asymmetries are at play. The rise timescales are longer for SLSNe than for normal SNe Ib/c, by roughly 10 days, for events with similar decay times. Thus, SLSNe-I can be considered as a separate population based on photometric properties. After peak, SLSNe-I decay with a wide range of slopes, with no obvious gap between rapidly declining and slowly declining events. The latter events show more irregularities (bumps) in the light curves at all times. At late times, the SLSN-I light curves slow down and cluster around the ^(56)Co radioactive decay rate. Powering the late-time light curves with radioactive decay would require between 1 and 10 M⊙ of Ni masses. Alternatively, a simple magnetar model can reasonably fit the majority of SLSNe-I light curves, with four exceptions, and can mimic the radioactive decay of ^(56)Co, up to ~400 days from explosion. The resulting spin values do not correlate with the host-galaxy metallicities. Finally, the analysis of our sample cannot strengthen the case for using SLSNe-I for cosmology.

Additional Information

© 2018 The American Astronomical Society. Received 2017 August 4; revised 2018 March 22; accepted 2018 March 23; published 2018 June 15. We thank the referee for a useful and constructive report, which helped make the paper more robust. We thank L. Dessart, A. Jerkstrand, A. Kozyreva, and the SLSN MIAPP 2017 workshop participants for insightful discussions. A.D.C. acknowledges support by the Weizmann Institute of Science Koshland Center for Basic Research. Support for I.A. was provided by NASA through the Einstein Fellowship Program, grant PF6-170148. M.S. acknowledges support from EU/FP7-ERC grant No. [615929]. K.M. acknowledges support from the STFC through an Ernest Rutherford Fellowship. E.O.O. is grateful for support by grants from the Israel Science Foundation, Minerva, Israeli ministry of Science, the US-Israel Binational Science Foundation and the I-CORE Program of the Planning and Budgeting Committee and The Israel Science Foundation. A.C. acknowledges support from the NSF CAREER award 1455090. M.M.K. acknowledges support from the GROWTH project funded by the National Science Foundation under grant No. 1545949. The intermediate Palomar Transient Factory project is a scientific collaboration among the California Institute of Technology, Los Alamos National Laboratory, the University of Wisconsin, Milwaukee, the Oskar Klein Center, the Weizmann Institute of Science, the TANGO Program of the University System of Taiwan, and the Kavli Institute for the Physics and Mathematics of the Universe. LANL participation in iPTF is supported by the US Department of Energy as a part of the Laboratory Directed Research and Development program. A portion of this work was carried out at the Jet Propulsion Laboratory under a Research and Technology Development Grant, under contract with the National Aeronautics and Space Administration. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research has made use of NASA's Astrophysics Data System. This paper made use of Lowell Observatory's Discovery Channel Telescope (DCT). Lowell operates the DCT in partnership with Boston University, Northern Arizona University, the University of Maryland, and the University of Toledo. Partial support of the DCT was provided by Discovery Communications. Large Monolithic Imager (LMI) on DCT was built by Lowell Observatory using funds from the National Science Foundation (AST-1005313). This work makes use of observations taken with the LCO network. This research has 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. 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. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Software: MS pipeline (Sullivan et al. 2006; Ofek et al. 2014a; Firth et al. 2015; Dimitriadis et al. 2017), LPIPE (http://www.astro.caltech.edu/~dperley/programs/lpipe.html), LCOGT pipeline (Valenti et al. 2016), HOTPANTS (http://www.astro.washington.edu/users/becker/v2.0/hotpants.html), IRAF (Tody 1986, 1993), SWarp (Bertin et al. 2002), DrizzlePac 2.0 (http://drizzlepac.stsci.edu).

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