Explosions in Accreting White Dwarfs: From Novae to Supernovae
Lars Bildsten
Kavli Institute for Theoretical Physics
U. C. Santa Barbara
March 17, 2008, 4PM, LPL 308
Many stellar binaries are orbiting so closely that matter flows from
one object to another. When the accreting star is a white dwarf, the
accumulated hydrogen eventually triggers a thermonuclear runaway
called a classical novae. These events are visible in nearby galaxies
and provide an inventory of the number of such binaries. We have
recently predicted a new kind of thermonuclear supernovae from Helium
that accretes onto white dwarfs in double white dwarf binaries. These
events eject 0.02-0.1 solar masses of radioactive elements that power
a faint and rapidly rising (few days) supernova every 10,000 years in
a typical elliptical galaxy. These ``.Ia'' supernovae (one-tenth as
bright for one-tenth the time as a Type Ia supernovae) should be found
in new surveys, yielding 1-30 .Ia supernovae per month. I will close
by summarizing the recent evidence for two distinct populations of
Type Ia supernovae that depend on the age of the galaxy in which these
'standardizable' candles explode.
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