Submitted on March 26, 2007
Accepted on June 29, 2007
Detection of Circumstellar Material in a Normal Type Ia Supernova
F. Patat 1*,
P. Chandra 2,
R. Chevalier 3,
S. Justham 4,
Ph. Podsiadlowski 4,
C. Wolf 4,
A. Gal-Yam 5,
L. Pasquini 1,
I. A. Crawford 6,
P. A. Mazzali 7,
A. W. A. Pauldrach 8,
K. Nomoto 9,
S. Benetti 10,
E. Cappellaro 10,
N. Elias-Rosa 11,
W. Hillebrandt 12,
D. C. Leonard 13,
A. Pastorello 14,
A. Renzini 10,
F. Sabbadin 10,
J. D. Simon 5,
M. Turatto 10
1 European Southern Observatory, K. Schwarzschild Str.2, 85748, Garching b. München, Germany.
2 University of Virginia, Department of Astronomy, Post Office Box 400325, Charlottesville, VA 22904, USA; Jansky Fellow, National Radio Astronomy Observatory
3 University of Virginia, Department of Astronomy, Post Office Box 400325, Charlottesville, VA 22904, USA.
4 Department of Astrophysics, University of Oxford, Oxford OX1 3RH, UK.
5 Astronomy Department, MS 105-24, California Institute of Technology, Pasadena, CA 91125, USA.
6 School of Earth Sciences, Birkbeck College London, Malet Street, London WC1E 7HX, UK.
7 Max-Planck-Institut für Astrophysik, K. Schwarzschild Str.1, 85748, Garching b. Muenchen, Germany; INAF-Osservatorio Astronomico, v. Tiepolo 11, 34131 Trieste, Italy.
8 Institut für Astronomie und Astrophysik der Ludwig-Maximilians-Universität, 81679 Munich, Germany.
9 Department of Astronomy, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
10 INAF-Osservatorio Astronomico, v. Osservatorio 5, 35122 Padova, Italy.
11 Max-Planck-Institut für Astrophysik, K. Schwarzschild Str.1, 85748, Garching b. Muenchen, Germany; Universidad de La Laguna, Av. Astrofísico Fransisco Sánchez s/n, E-38206, La Laguna, Tenerife, Spain.
12 Max-Planck-Institut für Astrophysik, K. Schwarzschild Str.1, 85748, Garching b. Muenchen, Germany.
13 Department of Astronomy, San Diego State University, San Diego, CA 92182, USA.
14 Astrophysics Research Centre, Queen's University Belfast, BT7 1NN, UK.
* To whom correspondence should be addressed.
F. Patat , E-mail: fpatat{at}eso.org
Type Ia supernovae are important cosmological distance indicators. These predictably-bright supernovae supposedly result from the thermonuclear explosion of a white dwarf star that exceeds some mass limit after accreting material from a companion, but the true nature of the progenitor star system is unknown. Here we report the spectroscopic detection of circumstellar material in a normal Type Ia supernova explosion. The expansion velocities, densities and dimensions of the circumstellar envelope indicate that this material was ejected from the progenitor system during the blast. In particular, the relatively low expansion velocities suggest that the white dwarf was accreting material from a companion star which is in the red-giant phase at the time of the explosion.
