Astronomy and Astrophysics – Astrophysics
Scientific paper
May 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995a%26a...297..509m&link_type=abstract
Astronomy and Astrophysics, v.297, p.509
Astronomy and Astrophysics
Astrophysics
75
Supernovae: Individual (Sn 1991T), Lines: Formation, Lines: Identification, Stars: Abundances, Nucleosynthesis
Scientific paper
A series of early-time optical spectra of SN 1991T have been modelled with our Monte Carlo code, in an effort to determine the properties of this peculiar SN Ia. The spectra, obtained from various observatories at epochs between 2 weeks before and 4 weeks after maximum, cover essentially the entire photospheric epoch of this SN. Synthetic spectra are presented, along with a reasonably complete identification of the spectral lines giving rise to the observed features. The fits were obtained adopting a reddening E(B-V)=0.13 and a Tully-Fisher distance modulus m-M=30.65 to NGC 4527. With these parameters, the model luminosities for SN 1991T are consistently about 0.5mag higher than in the `standard' SN Ia 1990N, while the photospheric velocities are slightly larger. The early suggestion that radioactive ^56^Ni and its daughter nuclei, ^56^Co and ^56^Fe, dominate the composition in the outer part of the ejecta, thus giving rise to pre-maximum spectra where Fe iii lines are the dominant features, is confirmed, but we show that the absence of the Si ii and Ca ii lines at that epoch is due simply to the high envelope temperature. This in turn is caused by the high luminosity of SN 1991T, which is a direct consequence of the overproduction of ^56^Ni. At times around and after maximum, however, the abundance of the Fe group elements drops relative to that of the intermediate mass elements. Eventually, the spectra obtained 3-4 weeks after maximum can be well fitted using the composition obtained by mixing the products of a deflagration model such as W7, although Si and Ca are underabundant. This indicates that the explosion mechanism active deep within the progenitor white dwarf, which was assumed to have a Chandrasekhar mass, must have been similar to the standard deflagration model. Thus, there is strong evidence that the peculiar explosion mechanism active in SN 1991T probably belonged to the family of delayed detonations, and led to Ni production in the outer layers of the exploding white dwarf. The spectral models suggest that about 0.6Msun_ of ^56^Ni have been synthesised in the outermost 1Msun_ of the exploding white dwarf, so that a factor between 1.5 and 1.7 more ^56^Ni was produced in SN 1991T than in SN 1990N. This result is fully consistent with the high luminosity required to fit the spectra.
Danziger Ivan John
Mazzali Paolo A.
Turatto Massimo
No associations
LandOfFree
A study of the properties of the peculiar SN IA 1991T through models of its evolving early-time spectrum. does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A study of the properties of the peculiar SN IA 1991T through models of its evolving early-time spectrum., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A study of the properties of the peculiar SN IA 1991T through models of its evolving early-time spectrum. will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1056177