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The rising light curves of Type Ia supernovae

The rising light curves of Type Ia supernovae
The rising light curves of Type Ia supernovae
We present an analysis of the early, rising light curves of 18 Type Ia supernovae (SNe Ia) discovered by the Palomar Transient Factory and the La Silla-QUEST variability survey. We fit these early data flux using a simple power law (f(t) = ? × tn) to determine the time of first light (t0), and hence the rise time (trise) from first light to peak luminosity, and the exponent of the power-law rise (n). We find a mean uncorrected rise time of 18.98 ± 0.54 d, with individual supernova (SN) rise times ranging from 15.98 to 24.7 d. The exponent n shows significant departures from the simple ‘fireball model’ of n = 2 (or f(t)???t2) usually assumed in the literature. With a mean value of n = 2.44 ± 0.13, our data also show significant diversity from event to event. This deviation has implications for the distribution of 56Ni throughout the SN ejecta, with a higher index suggesting a lesser degree of 56Ni mixing. The range of n found also confirms that the 56Ni distribution is not standard throughout the population of SNe Ia, in agreement with earlier work measuring such abundances through spectral modelling. We also show that the duration of the very early light curve, before the luminosity has reached half of its maximal value, does not correlate with the light-curve shape or stretch used to standardize SNe Ia in cosmological applications. This has implications for the cosmological fitting of SN Ia light curves.
0035-8711
3895-3910
Firth, R.E.
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Sullivan, M.
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Gal-Yam, A.
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Howell, D.A.
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Maguire, K.
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Nugent, P.
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Piro, A.L.
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Baltay, C.
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Feindt, U.
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Hadjiyksta, E.
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McKinnon, R.
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Ofek, E.
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Rabinowitz, D.
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Walker, E.S.
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Firth, R.E.
7ffbf088-47ec-44d1-a3bc-5caba4034fb3
Sullivan, M.
2f31f9fa-8e79-4b35-98e2-0cb38f503850
Gal-Yam, A.
21353e10-c914-495b-a841-b9b79b9b7954
Howell, D.A.
1a20d5f3-d2c4-43d6-88d7-c548eee8482f
Maguire, K.
94dfab90-b220-454f-8d2a-4ab4ffe27c65
Nugent, P.
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Piro, A.L.
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Baltay, C.
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Feindt, U.
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Hadjiyksta, E.
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McKinnon, R.
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Ofek, E.
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Rabinowitz, D.
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Walker, E.S.
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Firth, R.E., Sullivan, M., Gal-Yam, A., Howell, D.A., Maguire, K., Nugent, P., Piro, A.L., Baltay, C., Feindt, U., Hadjiyksta, E., McKinnon, R., Ofek, E., Rabinowitz, D. and Walker, E.S. (2015) The rising light curves of Type Ia supernovae. Monthly Notices of the Royal Astronomical Society, 446 (4), 3895-3910. (doi:10.1093/mnras/stu2314).

Record type: Article

Abstract

We present an analysis of the early, rising light curves of 18 Type Ia supernovae (SNe Ia) discovered by the Palomar Transient Factory and the La Silla-QUEST variability survey. We fit these early data flux using a simple power law (f(t) = ? × tn) to determine the time of first light (t0), and hence the rise time (trise) from first light to peak luminosity, and the exponent of the power-law rise (n). We find a mean uncorrected rise time of 18.98 ± 0.54 d, with individual supernova (SN) rise times ranging from 15.98 to 24.7 d. The exponent n shows significant departures from the simple ‘fireball model’ of n = 2 (or f(t)???t2) usually assumed in the literature. With a mean value of n = 2.44 ± 0.13, our data also show significant diversity from event to event. This deviation has implications for the distribution of 56Ni throughout the SN ejecta, with a higher index suggesting a lesser degree of 56Ni mixing. The range of n found also confirms that the 56Ni distribution is not standard throughout the population of SNe Ia, in agreement with earlier work measuring such abundances through spectral modelling. We also show that the duration of the very early light curve, before the luminosity has reached half of its maximal value, does not correlate with the light-curve shape or stretch used to standardize SNe Ia in cosmological applications. This has implications for the cosmological fitting of SN Ia light curves.

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Accepted/In Press date: 30 October 2014
e-pub ahead of print date: 9 December 2014
Published date: February 2015
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 394590
URI: https://eprints.soton.ac.uk/id/eprint/394590
ISSN: 0035-8711
PURE UUID: ef3f3448-c9b1-40fa-81ef-ed219a5858eb
ORCID for M. Sullivan: ORCID iD orcid.org/0000-0001-9053-4820

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Date deposited: 20 May 2016 14:37
Last modified: 06 Jun 2018 12:27

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