Pulsing Once Again

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Science  18 Feb 2011:
Vol. 331, Issue 6019, pp. 825
DOI: 10.1126/science.331.6019.825-c

Just as seismic waves allow scientists to study Earth's interior, stellar oscillations can tell us about the interior of stars. Cataclysmic variables are binary systems in which an extremely dense star, or white dwarf, accretes material from another star; in a dozen such cases so far, the white dwarf is known to pulsate. As their name suggests, cataclysmic variables can experience sudden outbursts—with the brightness of the entire system sometimes increasing by several orders of magnitude—when the accreted material undergoes thermonuclear fusion on the white dwarf's surface. The extent to which these events affect the white dwarf's interior is not completely understood.

The white dwarf in the cataclysmic variable SDSS J074531.92+453829.6 was shown to have stopped pulsating 1 year after its first recorded outburst, suggesting that it was heated to temperatures beyond those at which pulsations can occur. Now, 3 years after the outburst, Mukadam et al. show that the pulsations have resumed and that their properties, which depend on fundamental parameters such as the density, pressure, and temperature in the stellar interior, are similar to those of the pre-outburst pulsations. This white dwarf has thus cooled down to its previous state, with no signs of its interior having been perturbed by the outburst.

Astrophys. J. 728, L33 (2011).

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