SN 2011A: A low-luminosity interacting transient with a double plateau and strong sodium absorption

de Jaeger, T., Anderson, J. P., Pignata, G., Hamuy, M., Kankare, E., Stritzinger, M. D., Benetti, S., Bufano, F., Elias-Rosa, N., Folatelli, G., Förster, F., González-Gaitán, S., Gutiérrez, C. P., Inserra, C. ORCID: https://orcid.org/0000-0002-3968-4409, Kotak, R., Lira, P., Morrell, N., Taddia, F. and Tomasella, L. 2015. SN 2011A: A low-luminosity interacting transient with a double plateau and strong sodium absorption. Astrophysical Journal 807 (1) , 63. 10.1088/0004-637X/807/1/63

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Abstract

We present optical photometry and spectroscopy of the optical transient SN 2011A. Our data span 140 days after discovery including ${BVRI}\;u\prime g\prime r\prime i\prime z\prime $ photometry and 11 epochs of optical spectroscopy. Originally classified as a type IIn supernova (SN IIn) due to the presence of narrow Hα emission, this object shows exceptional characteristics. First, the light curve shows a double plateau, a property only observed before in the impostor SN 1997bs. Second, SN 2011A has a very low luminosity (${M}_{V}=-15.72$), placing it between normal luminous SNe IIn and SN impostors. Third, SN 2011A shows low velocity and high equivalent width absorption close to the sodium doublet, which increases with time and is most likely of circumstellar origin. This evolution is also accompanied by a change in line profile; when the absorption becomes stronger, a P Cygni profile appears. We discuss SN 2011A in the context of interacting SNe IIn and SN impostors, which appears to confirm the uniqueness of this transient. While we favor an impostor origin for SN 2011A, we highlight the difficulty in differentiating between terminal and non-terminal interacting transients.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Publisher:	American Astronomical Society
ISSN:	0004-637X
Date of First Compliant Deposit:	24 January 2019
Date of Acceptance:	5 May 2015
Last Modified:	05 May 2023 12:08
URI:	https://orca.cardiff.ac.uk/id/eprint/118776

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