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What Can We Learn from the Rising Lightcurves of Radioactively-Powered Supernovae?

Piro, Anthony L. and Nakar, Ehud (2013) What Can We Learn from the Rising Lightcurves of Radioactively-Powered Supernovae? Astrophysical Journal, 769 (1). Art. No. 67. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20121029-075611278

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Abstract

The light curve of the explosion of a star with a radius ≾ 10-100 R☉ is powered mostly by radioactive decay. Observationally, such events are dominated by hydrogen-deficient progenitors and classified as Type I supernovae (SNe I), i.e., white dwarf thermonuclear explosions (Type Ia), and core collapses of hydrogen-stripped massive stars (Type Ib/c). Current transient surveys are finding SNe I in increasing numbers and at earlier times, allowing their early emission to be studied in unprecedented detail. Motivated by these developments, we summarize the physics that produces their rising light curves and discuss ways in which observations can be utilized to study these exploding stars. The early radioactive-powered light curves probe the shallowest deposits of ^(56)Ni. If the amount of ^(56)Ni mixing in the outermost layers of the star can be deduced, then it places important constraints on the progenitor and properties of the explosive burning. In practice, we find that it is difficult to determine the level of mixing because it is hard to disentangle whether the explosion occurred recently and one is seeing radioactive heating near the surface or whether the explosion began in the past and the radioactive heating is deeper in the ejecta. In the latter case, there is a "dark phase" between the moment of explosion and the first observed light emitted once the shallowest layers of ^(56)Ni are exposed. Because of this, simply extrapolating a light curve from radioactive heating back in time is not a reliable method for estimating the explosion time. The best solution is to directly identify the moment of explosion, either through observing shock breakout (in X-ray/UV) or the cooling of the shock-heated surface (in UV/optical), so that the depth being probed by the rising light curve is known. However, since this is typically not available, we identify and discuss a number of other diagnostics that are helpful for deciphering how recently an explosion occurred. As an example, we apply these arguments to the recent SN Ic PTF 10vgv. We demonstrate that just a single measurement of the photospheric velocity and temperature during the rise places interesting constraints on its explosion time, radius, and level of ^(56)Ni mixing.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1088/0004-637X/769/1/67DOIArticle
http://iopscience.iop.org/article/10.1088/0004-637X/769/1/67/metaPublisherArticle
http://arxiv.org/abs/1210.3032arXivDiscussion Paper
ORCID:
AuthorORCID
Piro, Anthony L.0000-0001-6806-0673
Additional Information:© 2013 American Astronomical Society. Received 2012 October 8; accepted 2013 April 8; published 2013 May 6. We thank the anonymous referee for helpful comments and suggestions. We thank Eran Ofek for assistance in implementing the bolometric corrections for the P48, Avishay Gal-Yam for providing detailed comments, and Alessandra Corsi for helping with information about PTF 10vgv. We also thank Luc Dessart, Peter Goldreich, Christian Ott, and Re'em Sari for thoughtful discussions. A.L.P. was supported through NSF grants AST-1212170, PHY-1151197, and PHY-1068881, NASA ATP grant NNX11AC37G, NSF grant AST-0855535, and by the Sherman Fairchild Foundation. E.N. was partially supported by an ERC starting grant (GRB-SN 279369).
Group:TAPIR
Funders:
Funding AgencyGrant Number
NSFAST-1212170
NSFPHY-1151197
NSFPHY-1068881
NASANNX11AC37G
NSFAST-0855535
Sherman Fairchild FoundationUNSPECIFIED
European Research Council (ERC)GRB-SN 279369
Subject Keywords:hydrodynamics; shock waves; supernovae: general
Record Number:CaltechAUTHORS:20121029-075611278
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20121029-075611278
Official Citation:Anthony L. Piro and Ehud Nakar 2013 ApJ 769 67
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35139
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:01 Nov 2012 18:51
Last Modified:08 Sep 2017 16:12

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