Mode identification from time-resolved spectroscopy of the pulsating white dwarf G29‐38 |
| |
| Authors: | J. C. Clemens M. H. van Kerkwijk Y. Wu |
| |
| Affiliation: | Palomar Observatory, California Institute of Technology 105-24, Pasadena, CA 91125, USA; Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599-3255, USA; Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA; Astronomical Institute, Utrecht University, PO Box 80000, 3508 TA Utrecht, the Netherlands; Theoretical Astrophysics, California Institute of Technology 130-33, Pasadena, CA 91125, USA; Astronomy Unit, School of Mathematical Sciences, Queen Mary and Westfield College, Mile End Road, London E1 4NS |
| |
| Abstract: | ![]()
We have used time-resolved spectroscopy to measure the colour dependence of pulsation amplitudes in the DAV white dwarf G29-38. Model atmospheres predict that mode amplitudes should change with wavelength in a manner that depends on the spherical harmonic degree ℓ of the mode. This dependence arises from the convolution of mode geometry with wavelength-dependent limb darkening. Our analysis of the six largest normal modes detected in Keck observations of G29-38 reveals one mode with a colour dependence different from the other five, permitting us to identify the ℓ-value of all six modes and to test the model predictions. The Keck observations also show pulsation amplitudes that are unexpectedly asymmetric within absorption lines. We show that these asymmetries arise from surface motions associated with the non-radial pulsations (which are discussed in detail in a companion paper). By incorporating surface velocity fields into line profile calculations, we are able to produce models that more closely resemble the observations. |
| |
| Keywords: | stars: individual: G29-38 stars: oscillations white dwarfs |
|
|
