|
Author:
|
Taubenberger, S.; Hachinger, Stephan; Pignata, Giuliano; Mazzali, P. A.; Contreras, C.; Valenti, S.; Pastorello, A.; Elias-Rosa, Nancy; Bärnbantner, O.; Barwig, H.; Benetti, Stefano; Dolci, M.; Fliri, J.; Folatelli, Gastón; Freedman, Wendy L.; González, S.; Hamuy, Mario; Krzeminski, Wojtek; Morrell, Nidia; Navasardyan, H.; Persson, S. E.; Phillips, M. M.; Ries, C.; Roth, Miguel; Suntzeff, N. B.; Turatto, M.; Hillebrandt, W.
|
|
Abstract:
|
Optical observations of the Type Ia supernova (SN Ia) 2005bl in NGC 4070, obtained
from −6 to +66 d with respect to the B-band maximum, are presented. The photometric
evolution is characterised by rapidly-declining light curves ( m15(B)true = 1.93)
and red colours at peak and soon thereafter. With MB,max = −17.24 the SN is an
underluminous SN Ia, similar to the peculiar SNe 1991bg and 1999by. This similarity
also holds for the spectroscopic appearance, the only remarkable difference being
the likely presence of carbon in pre-maximum spectra of SN 2005bl. A comparison
study among underluminous SNe Ia is performed, based on a number of spectrophotometric
parameters. Previously reported correlations of the light-curve decline rate
with peak luminosity and R(Si) are confirmed, and a large range of post-maximum
Si ii 6355 velocity gradients is encountered. 1D synthetic spectra for SN 2005bl are
presented, which confirm the presence of carbon and suggest an overall low burning
efficiency with a significant amount of leftover unburned material. Also, the Fe content
in pre-maximum spectra is very low, which may point to a low metallicity of the
precursor. Implications for possible progenitor scenarios of underluminous SNe Ia are
briefly discussed. |