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Is SN 1987A Entering a New Phase of Evolution?

Published online by Cambridge University Press:  25 April 2016

R. A. Stathakis ,
R. D. Cannon  and
J. Spyromilio
R. A. Stathakis
Affiliation:
Anglo-Australian Observatory, PO Box 296, Epping, NSW 2121, Australia [email protected]
R. D. Cannon
Affiliation:
Anglo-Australian Observatory, PO Box 296, Epping, NSW 2121, Australia [email protected]
J. Spyromilio
Affiliation:
European Southern Observatory, Karl-Schwarzchild-Strasse 2, D-8046 Garching bei München, Germany
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Abstract

Optical spectra of the ejecta of SN 1987A taken at the AAT now cover seven years of evolution. In recent years, SN 1987A has been in a phase known as freeze-out. The timescales for recombination have exceeded those of energy deposition, and the ionisation structure has become fixed. During this phase, cooling is slow and the optical spectrum has been extremely stable. Our latest spectrum, however, shows significant change. [FeI] and [FeII] emission from iron-rich clumps has dominated the optical emission from the supernova over the last four years. All the [FeII] features have disappeared in our latest spectrum from December 1993 and model fits of [FeI] features indicate that these clumps have cooled to the critical temperature of 1000 K. They may be entering a phase of rapid cooling known as the infrared catastrophe. In addition, emission at high velocities has strengthened, in line with the predictions of freeze-out. SN 1987A may be entering a new, and previously unobserved, phase in supernova evolution.

Keywords

starssupernovaegeneralstarssupernovaeindividualSN 1987A
Type
Extragalactic
Information
Publications of the Astronomical Society of Australia , Volume 12 , Issue 1 , April 1995 , pp. 10 - 12
Copyright
Copyright © Astronomical Society of Australia 1995

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