ELFT HÍRADÓ

[Uhlár Karola <uhlar AT konkoly.hu>]

*MTA CSFK CSI RENDKÍVÜLI SZEMINÁRIUM*

Előadó:***Alejandro H. Córsico* (Universidad Nacional de La Plata, 
Argentina)

Előadás címe: *Constraining the axion mass through white dwarf 
asteroseismology*

Kivonat:
Axions are (still conjectural) non-baryonic particles considered as 
candidates for dark matter of the Universe. Their contribution to the 
dark matter depends on their mass, a quantity that is not given by the 
theory that predicts their existence. At the typical temperatures and 
densities found in the cores of white dwarfs, it is expected that 
copious emission of axions through bremsstrahlung processes takes place 
at the deepest regions of these stars. The mass of the axions determines 
how strongly they couple with electrons and, then, how large the axion 
emissivity is. Since axions can (almost) freely escape from the interior 
of white dwarfs, their existence would increase the cooling rate, with 
more massive axions producing larger additional cooling. Pulsating white 
dwarfs with hydrogen-rich atmospheres, also known as DAV or ZZ Ceti 
stars, can be used as astrophysical laboratories to constrain the 
properties of fundamental particles like axions by comparing the 
measured rates of period changes of these stars with the expected values 
from theoretical models.
In this talk, I will review the use of DAV white dwarfs as a tool to 
constrain the mass of the axion, and compare the predictions from this 
method with the results obtained through other approach that employs the 
white dwarf luminosity function (WDLF). In particular, the mass of the 
axion derived from pulsating white dwarfs is more than 3 times larger 
than the limit derived from the WDLF method. While the origin of this 
discrepancy is still unknown, I will focus on the fact that, in order 
that the results derived from pulsating white dwarfs be robust, it is 
necessary that the modes considered in the analysis be modes trapped in 
the outer H envelope of the star. I enumerate a few possibilities 
connected with the modeling of the previous evolutionary history of DA 
white dwarfs that could lead to these modes be non-trapped.

Előadás időpontja: *2013. december 10. (kedd), 14:00**
*
Előadás helyszíne: MTA CSFK CSI Előadóterme
1121 Budapest, Konkoly T. M. út 15-17.
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