Detection of Circumstellar Material in a Normal Type Ia Supernova
F. Patat,1*
P. Chandra,2
R. Chevalier,2
S. Justham,3
Ph. Podsiadlowski,3
C. Wolf,3
A. Gal-Yam,4
L. Pasquini,1
I. A. Crawford,5
P. A. Mazzali,6,7
A. W. A. Pauldrach,8
K. Nomoto,9
S. Benetti,10
E. Cappellaro,10
N. Elias-Rosa,6,11
W. Hillebrandt,6
D. C. Leonard,12
A. Pastorello,13
A. Renzini,10
F. Sabbadin,10
J. D. Simon,4
M. Turatto10
Type Ia supernovae are important cosmological distance indicators. Each of these bright supernovae supposedly results from the thermonuclear explosion of a white dwarf star that, after accreting material from a companion star, exceeds some mass limit, but the true nature of the progenitor star system remains controversial. 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. In particular, the relatively low expansion velocities suggest that the white dwarf was accreting material from a companion star that was in the red-giant phase at the time of the explosion.
1 European Southern Observatory (ESO), Karl Schwarzschild Strasse 2, 85748, Garching bei München, Germany.
2 University of Virginia, Department of Astronomy, Post Office Box 400325, Charlottesville, VA 22904, USA.
3 Department of Astrophysics, University of Oxford, Oxford OX1 3RH, UK.
4 Astronomy Department, MS 105-24, California Institute of Technology, Pasadena, CA 91125, USA.
5 School of Earth Sciences, Birkbeck College London, Malet Street, London WC1E 7HX, UK.
6 Max-Planck-Institut für Astrophysik, Karl Schwarzschild Strasse 1, 85748, Garching bei München, Germany.
7 Istituto Nazionale di Astrofisica (INAF)–Osservatorio Astronomico, via 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, vicolo Osservatorio 5, 35122 Padova, Italy.
11 Universidad de La Laguna, Avenida Astrofísico Francisco Sánchez s/n, E-38206, La Laguna, Tenerife, Spain.
12 Department of Astronomy, San Diego State University, San Diego, CA 92182, USA.
13 Astrophysics Research Centre, Queen's University Belfast, BT7 1NN, UK.
* To whom correspondence should be addressed. E-mail: fpatat{at}eso.org
