1202.5472 (Carles Badenes et al.)
Carles Badenes, Dan Maoz
We use multi-epoch spectroscopy of about 4000 white dwarfs in the Sloan
Digital Sky Survey to constrain the properties of the Galactic population of
binary white dwarf systems and calculate their merger rate. With a Monte Carlo
code, we model the distribution of DRVmax, the maximum radial velocity shift
between exposures of the same star, as a function of the binary fraction within
0.05 AU, fbin, and the power-law index in the separation distribution at the
end of the common envelope phase, alpha. Although there is some degeneracy
between fbin and alpha, the data constrain the combination of these parameters,
which determines a white dwarf merger rate per unit stellar mass of
1.4(+3.4,-1.0)e-13 /yr/Msun (1-sigma limits). This is remarkably similar to the
measured rate of Type Ia supernovae per unit stellar mass in Milky-Way-like Sbc
galaxies. The rate of super-Chandrasekhar mergers is only 1.0(+1.6,-0.6)e-14
/yr/Msun. We conclude that there are not enough close binary white dwarf
systems to reproduce the observed Type Ia SN rate in the 'classic' double
degenerate super-Chandrasekhar scenario. On the other hand, if
sub-Chandrasekhar mergers can lead to Type Ia SNe, as recently suggested by
some studies, they could make a major contribution to the overall Type Ia SN
rate.
View original:
http://arxiv.org/abs/1202.5472
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