Mathematics – Logic
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...211.2202k&link_type=abstract
American Astronomical Society, AAS Meeting #211, #22.02; Bulletin of the American Astronomical Society, Vol. 39, p.773
Mathematics
Logic
Scientific paper
We now have a good measurement of the cooling rate of G117-B15A, a remarkably stable pulsating white dwarf. In the near future, we will have equally well determined cooling rates for other stable pulsating white dwarfs, including R548. The ability to measure their cooling rates offers us a unique way to study weakly interacting particles that would contribute to their cooling. These particles include dark matter candidates. I performed a careful asteroseismological analysis of G117-B15A and R548 by carrying out a systematic, fine grid search for best fit models to the observed period spectra of those stars. In the initial search, I freely varied 4 parameters: the effective temperature, the stellar mass, the helium layer mass, and the hydrogen layer mass. Based on the results of that analysis and fits to the periods observed in R548 and G117-B15A, we can clearly define the regions of the 4 dimensional parameter space occupied by the best fit models. Combining those results with the spectroscopically determined mass and effective temperature, I define a plausible range of core compositions for the models. Using the best fit models, I computed rates of period change (dP/dt) for the 215s mode in G117-B15A and the 213s mode in R548, first for models that cool exclusively through the emission of photons and then for models with increasing emission rates of weakly interacting particles. Given the region of parameter space occupied by the models, I estimate error bars on the calculated dP/dt using Monte Carlo simulations and derive strong limits on the emission rates of weakly interacting particles in white dwarf interiors. In particular, I derive an upper mass limit for DFSZ axions.
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