Exploding Supermassive White Dwarfs from the Nearby Supernova Factory
Richard Scalzo
Yale University
Type Ia supernova (SNe Ia) have become popular in recent years as
luminosity distance indicators in cosmological experiments to study the
dark energy; however, the progenitor systems, explosion mechanisms,
and environments of these rare, luminous events are still poorly
understood. Most SNe Ia are believed to result from the thermonuclear
explosion of a single carbon-oxygen white dwarf, which accretes matter from
a non-degenerate binary companion star until it reaches the Chandrasekhar
limit (1.4 solar masses). After briefly reviewing the physics of SNe Ia
and their use in cosmology, I will present observations of an unusual
SN Ia, 2007if, from the Nearby Supernova Factory, a wide-area SN Ia
search and follow-up effort which ran from 2003 to 2008. The extreme
brightness of the SN and the low, slowly-changing expansion velocity of
the Si II 6355 absorption feature suggest that SN 2007if was probably a
merger of two white dwarfs with a total mass of 2.4 +/- 0.2 solar masses,
well in excess of the Chandrasekhar limit and at the edge of practical
limits allowed by evolution of stellar systems resulting in binary white
dwarfs. SN 2007if is a member of an emerging subclass of overluminous SN
Ia events which are thought to have super-massive progenitors, and its
properties help to clarify the physical nature of the subclass. These SNe
do not obey the usual light curve relations for luminosity standardization,
and may be merely the most extreme representatives of a broader subclass of
events which must be standardized separately or excluded from cosmological
Hubble diagrams.
Date: | Tuesday, 9 February 2010 |
Time: | 16:00 |
Where: | McGill University |
| Ernest Rutherford Physics Building, R.E. Bell Conference Room (room 103) |
Contact: | Robert Rutledge |
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