Nearby Supernova Factory Observations of SN 2005gj: Another TypeIa Supernova in a Massive Circumstellar Envelope

Journal Article · Thu Jun 01 00:00:00 EDT 2006 · The Astrophysical Journal

DOI:https://doi.org/10.1086/507020· OSTI ID:901222

Aldering, G; Antilogus, P; Bailey, S; Baltay, C; Bauer, A; Blanc, N; Bongard, S; Copin, Y; Gangler, E; Gilles, S; Kessler, R; Kocevski, D; Lee, B C; Loken, S; Nugent, P; Pain, R; Pecontal, E; Pereira, R; Perlmutter, S; Rabinowitz, D ; Rigaudier, G; Scalzo, R; Smadja, G; Thomas, R C; Wang, L; Weaver, B A; Rabinowitz, D; Bauer, A

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 interpret 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 interaction between the supernova ejecta and circumstellar material is much stronger than for SN 2002ic. Our .rst spectrum shows a hot continuum with broad and narrow H{alpha} emission. Later spectra, spanning over 4 months from outburst, show clear Type Ia features combined with broad and narrow H{gamma}, H{beta},H{alpha} and He I {lambda}{lambda}5876,7065 in emission. At higher resolution, P Cygni profiles are apparent. Surprisingly, we also observe an inverted P Cygni profile for [O III] {lambda}5007. We find that the lightcurve and measured velocity of the unshocked circumstellar material imply mass loss as recently as 8 years ago. This is in contrast to SN 2002ic, for which an inner cavity in the circumstellar material was inferred. Within the context of the thin-shell approximation, the early lightcurve is well-described by a flat radial density profile for the circumstellar material. However, our decomposition of the spectra into Type Ia and shock emission components allows for little obscuration of the supernova, suggesting an aspherical or clumpy distribution for the circumstellar material. We suggest that the emission line velocity profiles arise from electron scattering rather than the kinematics of the shock. This is supported by the inferred high densities, and the lack of evidence for evolution in the line widths. Ground- and space-based photometry, and Keck spectroscopy, of the host galaxy are used to ascertain that the host galaxy has low metallicity (Z/Z{sub {circle_dot}} < 0.3; 95% confidence) and that this galaxy is undergoing a significant star formation event that began roughly 200 {+-} 70 Myr ago. We discuss the implications of these observations for progenitor models and cosmology using Type Ia supernovae.

• Research Organization: Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
• Sponsoring Organization: USDOE Director. Office of Science. Office of AdvancedScientific Computing Research. Office of High Energy Physics, YaleUniversity; National Science Foundation Grant AST-0407297 andANI-0087344, National Aeronautics and Space Administration; Alfred PSloan Foundation, Participating Institutions, Japanese Monbukagakusho,Max Planck Society, CNRS/IN2P3, CNRS/INSU, PNC, MooreFoundation
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 901222
• Report Number(s): LBNL--59837; BnR: KA1301020
• Journal Information: The Astrophysical Journal, Journal Name: The Astrophysical Journal Journal Issue: pt1 Vol. 650
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
COSMOLOGY
DISTRIBUTION
ELECTRONS
EXPLOSIONS
LINE WIDTHS
PHOTOMETRY
RESOLUTION
SCATTERING
SPECTRA
SPECTROSCOPY
STARS
SUPERNOVAE
VELOCITY