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Observations of the Progenitor Wind of SN 1987A

Published online by Cambridge University Press:  12 April 2016

E.J. Wampler ,
A. Richichi  and
D. Baade
E.J. Wampler
Affiliation:
European Southern Observatory, Garching
A. Richichi
Affiliation:
Arcetri Observatory, Firenze
D. Baade
Affiliation:
European Southern Observatory, Garching

Abstract

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As part of a general ESO program to monitor the spectrum of SN 1987A, we are collecting intermediate high resolution (R = λ/Δλ ≈ 2x104) spectra of the supernova. By the end of the year 1987 it was possible to see narrow emission features due to [OIII] and hydrogen in spectra taken with the ESO Cassegrain echelle spectrograph (CASPEC) (Wampler and Richichi 1988, 1989). At that time, the velocities of these lines were about 286 km/sec and their widths were about 14 km/sec (FWHM). It is almost certain that these lines arise from a cloud of highly ionized gas that was first detected in ultraviolet spectra obtained by IUE in May 1987 (Fransson et al. 1989). This cloud is presumably a circumstellar shell that surrounded the progenitor of SN 1987A and was ionized by the initial UV flash from the supernova explosion. In the ideal case of an expanding spherical shell that is large enough for light travel times to be important, one would expect the intensity of an emission line to increase and then decrease again as the light from the front of the shell fades. At the same time the velocity of the line would increase as the integrated light became dominated by light from the back (receding) hemisphere. The IUE light curve (Fransson et al. 1989) for the ultraviolet [NV] line was consistent with the photometric behavior expected from a nebula about 400 light days in diameter. At the distance of the LMC, one light year is equal to a span of one arc-second, and the photometric behavior of [NV] is consistent with the extent of the nebula measured by Wampler and Richichi (1989).

Type
II. Mechanical Energy Sources
Information
International Astronomical Union Colloquium , Volume 120: Structure and Dynamics of the Interstellar Medium , 1989 , pp. 180 - 185
Copyright
Copyright © Springer-Verlag 1989

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