Mode identification from time-resolved spectroscopy of the pulsating white dwarf G29-38

Keck Speckle Imaging of the White Dwarf G29-38: No Brown Dwarf Companion Detected

The white dwarf Giclas 29-38 has attracted much attention due to its large infrared excess and the suggestion that excess might be due to a companion brown dwarf. We observed this object using speckle interferometry at the Keck telescope, obtaining diffraction-limited resolution (55 milliarcseconds) at K band, and found it unresolved. Assuming the entire K band excess is due to a single point-l...

Discovery of Photospheric Calcium Line-Strength Variations in the Dazd White Dwarf G29-38

Metals in the photospheres of white dwarfs with TeA between 12,000 and 25,000 K should gravitationally settle out of these atmospheres in 1Y2 weeks. Temporal variations in the line strengths of these metals could provide a direct measurement of episodic metal accretion. Using archival VLTand Keck spectroscopy, we find evidence that the DAZd white dwarf G29-38 shows significant changes in its Ca...

On mode trapping in pulsating DA white dwarf stars

The present work is designed to explore the effects of the time-dependent element diffusion on the mode trapping properties of DA white dwarf models with various thickness of the hydrogen envelope. Our predictions are compared with the standard assumption of diffusive equilibrium in the trace element approximation. We find that element diffusion markedly weakens the presence of mode trapping or...

Mode identification of Pulsating White Dwarfs using the HST 1

Surface motion in the pulsating DA white dwarf G 29 - 38

We present time-resolved spectrophotometry of the pulsating DA white dwarf G 29-38. As in previous broad-band photometry, the light curve shows the presence of a large number of periodicities. Many of these are combination frequencies, i.e., periodicities occurring at frequencies that are sums or differences of frequencies of stronger, real modes. We identify at least six real modes, and at lea...