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Constraints on Shallow ^(56)Ni from the Early Light curves of Type Ia Supernovae

Piro, Anthony L. and Nakar, Ehud (2014) Constraints on Shallow ^(56)Ni from the Early Light curves of Type Ia Supernovae. Astrophysical Journal, 784 (1). Art. No. 85. ISSN 0004-637X. doi:10.1088/0004-637X/784/1/85.

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Ongoing transient surveys are presenting an unprecedented account of the rising light curves of Type Ia supernovae (SNe Ia). This early emission probes the shallowest layers of the exploding white dwarf (WD), which can provide constraints on the progenitor star and the properties of the explosive burning. We use semianalytic models of radioactively powered rising light curves to analyze these observations. As we have summarized in previous work, the main limiting factor in determining the surface distribution of ^(56)Ni is the lack of an unambiguously identified time of explosion, as would be provided by detection of shock breakout or shock-heated cooling. Without this the SN may in principle exhibit a "dark phase" for a few hours to days, where the only emission is from shock-heated cooling that is too dim to be detected. We show that by assuming a theoretically motivated time-dependent velocity evolution, the explosion time can be better constrained, albeit with potential systematic uncertainties. This technique is used to infer the surface ^(56)Ni distributions of three recent SNe Ia that were caught especially early in their rise. In all three we find fairly similar ^(56)Ni distributions. Observations of SN 2011fe and SN 2012cg probe shallower depths than SN 2009ig, and in these two cases 56Ni is present merely ~10^(–2) M_☉ from the WDs' surfaces. The uncertainty in this result is up to an order of magnitude given the difficulty of precisely constraining the explosion time. We also use our conclusions about the explosion times to reassess radius constraints for the progenitor of SN 2011fe, as well as discuss the roughly t^2 power law that is inferred for many observed rising light curves.

Item Type:Article
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URLURL TypeDescription Paper
Piro, Anthony L.0000-0001-6806-0673
Nakar, Ehud0000-0002-4534-7089
Alternate Title:Constraints on Shallow ^(56)Ni from the Early Lightcurves of Type Ia Supernovae
Additional Information:© 2014 American Astronomical Society. Received 2012 November 26; accepted 2014 February 13; published 2014 March 6. We thank Ryan Foley, Mohan Ganeshalingam, and Jeffrey Silverman for assistance with assessing data and discussing observations. We also thank Federica Bianco, Ryan Chornock, Luc Dessart, Stephan Hachinger, Keiichi Maeda, Peter Nugent, and Re’em Sari for helpful discussions or comments on previous drafts. A.L.P. was supported through NSF grants AST-1212170, PHY-1151197, and PHY-1068881, NASA ATP grant NNX11AC37G, and by the Sherman Fairchild Foundation. E.N. was partially supported by an ERC starting grant (GRB-SN 279369) and by the I-CORE Program of the Planning and Budgeting Committee and the ISF (1829/12).
Funding AgencyGrant Number
Sherman Fairchild FoundationUNSPECIFIED
European Research Council (ERC)GRB-SN 279369
I-CORE Program Planning and Budgeting CommitteeUNSPECIFIED
Israel Science Foundation1829/12
Subject Keywords:hydrodynamics; shock waves; supernovae: general; white dwarfs
Issue or Number:1
Record Number:CaltechAUTHORS:20130123-100143273
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Official Citation:Constraints on Shallow 56Ni from the Early Light Curves of Type Ia Supernovae Anthony L. Piro and Ehud Nakar 2014 ApJ 784 85
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36530
Deposited By: Ruth Sustaita
Deposited On:23 Jan 2013 18:16
Last Modified:09 Nov 2021 23:22

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