Nearby Supernova Factory Observations of SN 2005gj: Another Type Ia Supernova in a Massive Circumstellar Envelope.

Revision 2.6, 2006/06/01 00:20:07 Nearby Supernova Factory Observations of SN 2005gj: Another Type Ia Supernova in a Massive Circumstellar Envelope. The Nearby Supernova Factory G. Aldering, P. Antilogus, S. Bailey, 1 C. Baltay, 8 A. Bauer, 8 N. Blanc, 2 S. Bongard, 1,5 Y. Copin, 2 E. Gangler, 2 S. Gilles, 3 R. Kessler, 7 D. Kocevski, 1,6 B. C. Lee, 1 S. Loken, 1 P. Nugent, 1 R. Pain, 3 E. P´ contal, 4 R. Pereira, 3 S. Perlmutter, 1,6 D. Rabinowitz, 8 e G. Rigaudier, R. Scalzo, G. Smadja, 2 R. C. Thomas, 1 L. Wang, 1 B. A. Weaver 1,5 ABSTRACT We report the independent discovery and follow-up observations of supernova 2005gj by the Nearby Supernova Factory. This is the second confirmed case of a “hybrid” Type Ia/IIn supernova, which like the prototype SN 2002ic, we inter- pret as the explosion of a white dwarf interacting with a circumstellar medium. Our early-phase photometry of SN 2005gj shows that the strength of the inter- action between the supernova ejecta and circumstellar material is much stronger than for SN 2002ic. Our first spectrum shows a hot continuum with broad and narrow Hα emission. Later spectra, spanning over 4 months from outburst, show clear Type Ia features combined with broad and narrow Hγ, Hβ, Hα and He I λλ5876,7065 in emission. At higher resolution, P Cygni profiles are appar- ent. Surprisingly, we also observe an inverted P Cygni profile for [O III ] λ5007. Physics Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720 Institut de Physique Nucl´ aire de Lyon, UMR5822, CNRS-IN2P3; Universit´ Claude Bernard Lyon 1, e e F-69622 Villeurbanne France Laboratoire de Physique Nucl´ aire et des Hautes Energies IN2P3 - CNRS - Universit´ s Paris VI et Paris e e VII, 4 place Jussieu Tour 33 - Rez de chauss´ e 75252 Paris Cedex 05 e Centre de Recherche Astronomique de Lyon, 9, av. Charles Andr´ , 69561 Saint Genis Laval Cedex e University of California, Space Sciences Laboratory, Berkeley, CA 94720-7450 Department of Physics, University of California, Berkeley, CA 94720 Kavli Institute for Cosmological Physics, The University of Chicago, Chicago, IL 60637 Department of Physics, Yale University, New Haven, CT 06250-8121