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SN 1994W: Evidence of Explosive Mass Ejection a Few Years Before Explosion

Published online by Cambridge University Press:  19 September 2016

Nikolai N. Chugai
Affiliation:
Institute of Astronomy, RAS, Pyatnitskaya 48, 109017 Moscow, Russia; [email protected]
Robert J. Cumming
Affiliation:
Stockholm Observatory, AlbaNova University Center, 106 61 Stockholm, [email protected], [email protected]
Sergei I. Blinnikov
Affiliation:
ITEP, 117218 Moscow, [email protected]
Peter Lundqvist
Affiliation:
Stockholm Observatory, AlbaNova University Center, 106 61 Stockholm, [email protected], [email protected]
Alexei V. Filippenko
Affiliation:
Department of Astronomy, University of California at Berkeley, Berkeley, CA 94720-3411, USA
Aaron J. Barth
Affiliation:
Department of Astronomy, University of California at Berkeley, Berkeley, CA 94720-3411, USA
Angela Bragaglia
Affiliation:
Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
Douglas C. Leonard
Affiliation:
Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003-9305, USA
Thomas Matheson
Affiliation:
Harvard-Smithsonian Center for Astrophysics, Mail Stop 20, 60 Garden Street, Cambridge, MA 02138, USA
Jesper Sollerman
Affiliation:
Stockholm Observatory, AlbaNova University Center, 106 61 Stockholm, [email protected], [email protected]

Summary

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We present and analyze spectra of the Type IIn supernova 1994W obtained between 18 and 202 days after explosion. During the first 100 days the line profiles are composed of three major components: (i) narrow P Cygni lines with absorption minima at −700 km s−1; (ii) broad emission lines with blue velocity at zero intensity ~ 4000 km s−1; (iii) broad, smooth, extended wings most apparent in Hα. These components are identified with the expanding circumstellar (CS) envelope [5], shocked cool gas in the forward postshock region, and multiple Thomson scattering in the CS envelope, respectively. The absence of broad P Cygni lines from the supernova (SN) is the result of the formation of an optically thick, cool, dense shell at the interface of the ejecta and the CS envelope. Models of the SN deceleration and Thomson scattering wings are used to recover the Thomson optical depth of the CS envelope, τT ≥ 2.5 during first month, its density (n ~ 109 cm-3) and radial extent, ~ (4 — 5) × 1015 cm. The plateau-like SN light curve, which we reproduce by a hydrodynamical model, is powered by a combination of internal energy leakage after the explosion of an extended presupernova (~ 1015 cm) and subsequent luminosity from circumstellar interaction. We recover the pre-explosion kinematics of the CS envelope and find it to be close to homologous expansion with outmost velocity ≈ 1100 km s-1 and a kinematic age of ~ 1.5 yr. The high mass (≈ 0.4 M) and kinetic energy (≈ 2 × 1048 erg) of the CS envelope combined with small age strongly suggest that the CS envelope was explosively ejected only a few years before the SN explosion.

Type
Part I Supernovae: Individual
Copyright
Copyright © Springer-Verlag 2005

References

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