Thirty Years of SN 1980K: Evidence for Light Echoes

Sugerman, Ben E. K.; Andrews, Jennifer E.; Barlow, Michael J.; Clayton, Geoffrey C.; Ercolano, Barbara; Ghavamian, Parviz; Kennicutt, Robert C., Jr.; Krause, Oliver; Meixner, Margaret; Otsuka, Masaaki

Publication

The Astrophysical Journal, Volume 749, Issue 2, article id. 170 (2012). (ApJ Homepage)

Publication Date

04/2012

Origin

IOP

Astronomy Keywords

circumstellar matter, dust, extinction, methods: numerical, radiative transfer, supernovae: individual: SN 1980K

DOI

10.1088/0004-637X/749/2/170

Bibliographic Code

2012ApJ...749..170S

Abstract

We report optical and mid-infrared photometry of SN 1980K between 2004 and 2010, which shows slow monotonic fading consistent with previous spectroscopic and photometric observations made 8-17 yr after outburst. The slow rate of change over two decades suggests that this evolution may result from scattered and thermal light echoes off of extended circumstellar material. We present a semi-analytic dust radiative-transfer model that uses an empirically corrected effective optical depth to provide a fast and robust alternative to full Monte Carlo radiative-transfer modeling for homogenous dust at low to intermediate optical depths. We find that unresolved echoes from a thin circumstellar shell 14-15 lt-yr from the progenitor, and containing <~ 0.02 M sun of carbon-rich dust, can explain the broadband spectral and temporal evolution. The size, mass, and dust composition are in good agreement with the contact discontinuity observed in scattered echoes around SN 1987A. The origin of slowly changing high-velocity [O I] and Hα lines is also considered. We propose an origin in shocked high-velocity metal-rich clumps of ejecta, rather than arising in the impact of ejecta on slowly moving circumstellar material, as is the case with hot spots in SN 1987A.

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