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For refcode 1989ApJ...338..388E:
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1989ApJ...338..388E CIRCUMSTELLAR INFRARED AND SCATTERED LIGHT ECHOES FROM SN 1987A ROBERT T. EMMERING AND ROGER A. CHEVALIER Department of Astronomy, University of Virginia Received 1988 May 2; accepted 1988 August 11 ABSTRACT We use the observed light curve and temperature evolution, as well as the theoretically predicted initial ultraviolet (UV) burst, of SN 1987A to construct models for the infrared (IR) echo and scattered light echo arising from circumstellar dust formed in the wind from the supernova progenitor's red supergiant phase. Observations of narrow UV emission lines suggest that some of this wind has been swept into a shell with a radius of order R_s_ ~ 10^18^ cm by the progenitor's blue supergiant wind. The UV observations also indicate a high abundance of oxygen with respect to carbon which implies that the circumstellar dust should be composed primarily of silicate grains. Our echo models are constructed by including the detailed emission and scattering properties of silicate grains, and we consider a spectrum of grain sizes. The comparison of the predictions of our IR echo models with the available IR observations lead us to conclude that an IR echo has probably not been observed as of 1987 August. We find that the mass of the shell must be less than ~ 10 M_sun_ (R_s_/10^18^ cm)^3^. The comparison of the observed UV flux from SN 1987A with our scattered light echo models implies that the mass of the shell must be less than ~4 M_sun_ (R_s_/10^18^ cm)^3^ if the dust is composed of small grains (radius ~0.01 micron), and must be less than ~0.1 M_sun_ (R_s_/10^18^cm)^3^ if the dust is composed of large grains (radius ~ 0.25 mircon); however, these conclusions are sensitive to the properties of the unobserved initial UV burst. The methods that we have developed to study the effects of circumstellar dust around SN 1987A should be applicable to observations of other supernovae. Subject headings: stars: circumstellar shells - stars: individual (SN 1987A) - stars: supernovae
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