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The Composite Image of Sanduleak −69° 202, Candidate Precursor to SN 1987A in the LMC

Published online by Cambridge University Press:  12 April 2016

Nolan R. Walborn
Affiliation:
Space Telescope Science Institute
Barry M. Lasker
Affiliation:
Space Telescope Science Institute
Victoria G. Laidler
Affiliation:
Astronomy Programs, Computer Sciences Corporation
You-Hua Chu
Affiliation:
Astronomy Department, University of Illinois

Extract

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The image of Sk −69° 202 was scanned and analyzed on eight (of 32 available) blue through near-infrared photographic plates obtained at the prime focus of the Cerro Tololo Inter-American Observatory 4-meter telescope during 1974–1983. Both intensity syntheses of the image and density differences were derived by means of reference stars from the same plates, including the similar nearby object Sk −69° 203. Several of the density differences are shown in Figure 1. The analysis shows that the 12m blue supergiant in Sk −69° 202 (Star 1) has two companions with V magnitudes, position angles, and separations 315°, 3″ (Star 2) and 115°, 1.″5 (Star 3), respectively. Both companions appear to be early-type stars; there is no evidence for a bright red star in the system. The two companions are responsible for the spectra observed by the International Ultraviolet Explorer following the decline of the SN in the far UV, so that Star 1 has disappeared and was probably the progenitor. The most likely interpretation is that it was a post-red supergiant evolving blueward in the HR diagram.

Type
Part III. Chemical and Dynamical Structures of Exploding Stars
Copyright
Copyright © Springer-Verlag 1988