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Published March 2009 | Published + Supplemental Material
Journal Article Open

SN 1994W: an interacting supernova or two interacting shells?

Abstract

We present a multi-epoch quantitative spectroscopic analysis of the Type IIn supernova (Type IIn SN) 1994W, an event interpreted by Chugai et al. as stemming from the interaction between the ejecta of a SN and a 0.4 M_⊙ circumstellar shell ejected 1.5 yr before core collapse. During the brightening phase, our models suggest that the source of optical radiation is not unique, perhaps associated with an inner optically thick cold dense shell and outer optically thin shocked material. During the fading phase, our models support a single source of radiation, an hydrogen-rich optically thick layer with a near-constant temperature of ~7000 K that recedes from a radius of 4.3 × 10^15 at a peak to 2.3 × 10^15 cm 40 d later. We reproduce the hybrid narrow-core broad-wing line profile shapes of SN 1994W at all times, invoking an optically thick photosphere exclusively (i.e. without any external optically thick shell). In SN 1994W, slow expansion makes scattering with thermal electrons a key escape mechanism for photons trapped in optically thick line cores, and allows the resulting broad incoherent electron-scattering wings to be seen around narrow-line cores. In SNe with larger expansion velocities, the thermal broadening due to incoherent scattering is masked by the broad profile and the dominant frequency redshift occasioned by bulk motions. Given the absence of broad lines at all times and the very low ^(56)Ni yields, we speculate whether SN 1994W could have resulted from an interaction between two ejected shells without core collapse. The high conversion efficiency of kinetic to thermal energy may not require a SN-like energy budget for SN1994W.

Additional Information

© 2009 The Authors. Journal compilation © 2009 RAS. Accepted 2008 October 2. Received 2008 September 11; in original form 2008 April 2. We thank Adam Burrows, Rubina Kotak, Jeremiah Murphy and Steve Smartt for discussion, Robert Cumming for providing the SN 1994W spectroscopic data used here, Nikolai Chugai for his comments and Stéphane Blondin for a thorough reading of a draft of this paper and his suggestions. LD acknowledges support for this work from the Scientific Discovery through Advanced Computing (SciDAC) program of the DOE, under grant numbers DOE-FC02-01ER41184 and DOE-FC02-06ER41452, and the NSF under grant number AST-0504947.

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Published - Dessart2009p59910.1111j.1365-2966.2008.14042.x.pdf

Supplemental Material - sm001.zip

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Additional details

Created:
August 21, 2023
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October 18, 2023