Optical spectrum of SN 1978K: emission from shocked clouds in the circumstellar wind
Date Issued
1995
Author(s)
Abstract
An optical spectrum of SN 1978K (NGC 1313) in the range of 4000-7200 A was obtained on 1992 October 22, i.e. 14.4 yr after the outburst. The spectrum is still dominated by the narrow (FWHM<=560 km s^-1) Hα line having a luminosity 2.2x10^38 erg s^-1 (D=3.7 Mpc, A_V=0.64 mag), 1.5-2 times lower than the values derived from published data for 1989 December and 1990 October. There is no evidence for a broad Hα component (HWZI~3000-10000 km s^-1) with an upper limit of luminosity ~3x10^36 erg s^-1. We suggest that the optical emission of SN 1978K originates from radiative shock waves propagating in the dense (~4x10^6 cm^-3) clouds of a circumstellar wind. The cloud shock waves are driven by the expanding low-mass (M<=2M_solar) supernova ejecta with the present radius ~(2-3)x10^17 cm. The mass of circumstellar material involved in the dynamical interaction is ~=1M_solar and the corresponding mass-loss rate of pre-SN wind is ~2x10^-4 M_solar yr^-1. The observed X-ray emission is attributed to the shock waves in the boundary layer of the same population of clouds. Alternatively, however, the X-ray emission might emanate from the shock waves in a different cloud population with a lower density.
Volume
276
Issue
2
Start page
530
Issn Identifier
0035-8711
Ads BibCode
1995MNRAS.276..530C
Rights
open.access
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