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Published April 2016 | Submitted + Published
Journal Article Open

Long-rising Type II supernovae from Palomar Transient Factory and Caltech Core-Collapse Project

Abstract

Context. Supernova (SN) 1987A was a peculiar hydrogen-rich event with a long-rising (~ 84 d) light curve, stemming from the explosion of a compact blue supergiant star. Only a few similar events have been presented in the literature in recent decades. Aims. We present new data for a sample of six long-rising Type II SNe (SNe II), three of which were discovered and observed by the Palomar Transient Factory (PTF) and three observed by the Caltech Core-Collapse Project (CCCP). Our aim is to enlarge this small family of long-rising SNe II, characterizing their differences in terms of progenitor and explosion parameters. We also study the metallicity of their environments. Methods. Optical light curves, spectra, and host-galaxy properties of these SNe are presented and analyzed. Detailed comparisons with known SN 1987A-like events in the literature are shown, with particular emphasis on the absolute magnitudes, colors, expansion velocities, and host-galaxy metallicities. Bolometric properties are derived from the multiband light curves. By modeling the early time emission with scaling relations derived from the SuperNova Explosion Code (SNEC) models of MESA progenitor stars, we estimate the progenitor radii of these transients. The modeling of the bolometric light curves also allows us to estimate other progenitor and explosion parameters, such as the ejected ^(56)Ni mass, the explosion energy, and the ejecta mass. Results. We present PTF12kso, a long-rising SN II that is estimated to have the largest amount of ejected ^(56)Ni mass measured for this class. PTF09gpn and PTF12kso are found at the lowest host metallicities observed for this SN group. The variety of early light curve luminosities depends on the wide range of progenitor radii of these SNe, from a few tens of R_⊙ (SN 2005ci) up to thousands (SN 2004ek) with some intermediate cases between 100 R_⊙ (PTF09gpn) and 300 R_⊙ (SN 2004em). Conclusions. We confirm that long-rising SNe II with light-curve shapes closely resembling that of SN 1987A generally arise from blue supergiant (BSG) stars. However, some of them, such as SN 2004em, likely have progenitors with larger radii (~ 300 R_⊙, typical of yellow supergiants) and can thus be regarded as intermediate cases between normal SNe IIP and SN 1987A-like SNe. Some extended red supergiant (RSG) stars such as the progenitor of SN 2004ek can also produce long-rising SNe II if they synthesized a large amount of ^(56 0Ni in the explosion. Low host metallicity is confirmed as a characteristic of the SNe arising from compact BSG stars.

Additional Information

© 2016 ESO. Received 23 November 2015. Accepted 23 January 2016. We thank the staffs of the various observatories (Palomar, Lick, Keck, etc.) where data for this study were obtained. The Oskar Klein Centre is funded by the Swedish Research Council. We gratefully acknowledge the support from the Knut and Alice Wallenberg Foundation. A.G.-Y. is supported by the EU/FP7 via ERC grant No. 307260, the Quantum Universe I-Core program by the Israeli Committee for Planning and Budgeting and the ISF; by Minerva and ISF grants; by the Weizmann-UK "making connections" program; and by Kimmel and ARCHES awards. A.V.F.'s research is supported by the Christopher R. Redlich Fund, the TABASGO Foundation, and NSF grant AST-1211916. D.C.L. and S.F.A. acknowledge support from NSF grants AST-1009571 and AST-1210311, under which part of this research (photometry data collected at MLO) was carried out. We thank Joseph Fedrow, Alyssa Del Rosario, Chuck Horst, and David Jaimes for assistance with the MLO observations. J.M.S. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1302771. This research has made use of the APASS database, located at the AAVSO web site; funding for APASS has been provided by the Robert Martin Ayers Sciences Fund. Research at Lick Observatory is partially supported by a generous gift from Google. 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 NASA; the observatory was made possible by the generous financial support of the W. M. Keck Foundation. We acknowledge contributions to CCCP by S. B. Cenko, D. Fox, D. Sand, and A. Soderberg. We acknowledge M. Sullivan and K. Sharon for helping with the CCCP spectral observations. LANL participation in iPTF is supported by the US Department of Energy as part of the Laboratory Directed Research and Development program.

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Published - aa27811-15.pdf

Submitted - 1601.07368v1.pdf

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Created:
August 20, 2023
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