Deciphering the Pulsations of G 29-38 with Optical Time Series Spectroscopy

Abstract

We present optical time series spectroscopy of the pulsating white dwarf star G29-38 taken at the Very Large Telescope (VLT). By measuring the variations in brightness, Doppler shift, and line shape of each spectrum, we explore the physics of pulsation and measure the spherical degree ($\ell$) of each stellar pulsation mode. We measure the physical motion of the g-modes correlated with the brightness variations for three of the eight pulsation modes in this data set. The varying line shape reveals the spherical degree of the pulsations, an important quantity for properly modeling the interior of the star with asteroseismology. Performing fits to the H$\beta$, H$\gamma$, and H$\delta$ lines, we quantify the changing shape of the line and compare them to models and previous time series spectroscopy of G~29-38. These VLT data confirm several $\ell$ identifications and add four new values, including an additional $\ell$=2 and a possible $\ell$=4. In total from both sets of spectroscopy of G29-38, eleven modes now have known spherical degrees.

arXiv commentAccepted for publication by MNRAS

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• Toward ensemble asteroseismology of ZZ Ceti stars with fully evolutionary models
• Discovery of Molecular Hydrogen in White Dwarf Atmospheres
• Pulsational Mapping of Calcium Across the Surface of a White Dwarf
• Asteroseismology of DAV star EC14012-1446, mode identification and model fittings
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• Asteroseismology of DAV white dwarf stars and G29-38