Signatures of an eruptive phase before the explosion of the peculiar core-collapse SN 2013gc
Date Issued
2019
Author(s)
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Pignata, G.
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Agliozzo, C.
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Morrell, N. I.
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Olivares E., F.
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Reichart, D. E.
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Haislip, J. B.
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Kouprianov, V.
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Smartt, S. J.
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Ciroi, S.
Abstract
We present photometric and spectroscopic analysis of the peculiar core-collapse supernova (SN) 2013gc, spanning 7 yr of observations. The light curve shows an early maximum followed by a fast decline and a phase of almost constant luminosity. At +200 d from maximum, a brightening of 1 mag is observed in all bands, followed by a steep linear luminosity decline after +300 d. In archival images taken between 1.5 and 2.5 yr before the explosion, a weak source is visible at the supernova location, with mag ≈20. The early supernova spectra show Balmer lines, with a narrow (∼560 km s-1) P-Cygni absorption superimposed on a broad (∼3400 km s-1) component, typical of Type IIn events. Through a comparison of colour curves, absolute light curves, and spectra of SN 2013gc with a sample of supernovae IIn, we conclude that SN 2013gc is a member of the so-called Type IId subgroup. The complex profile of the H α line suggests a composite circumstellar medium geometry, with a combination of lower velocity, spherically symmetric gas, and a more rapidly expanding bilobed feature. This circumstellar medium distribution has been likely formed through major mass-loss events that we directly observed from 3 yr before the explosion. The modest luminosity (MI ∼ -16.5 near maximum) of SN 2013gc at all phases, the very small amount of ejected 56Ni (of the order of 10-3 M☉), the major pre-supernova stellar activity, and the lack of prominent [O I] lines in the late-time spectra support a fall-back core-collapse scenario for the massive progenitor of SN 2013gc.
Volume
482
Issue
2
Start page
2750
Issn Identifier
0035-8711
Ads BibCode
2019MNRAS.482.2750R
Rights
open.access
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