HST Observations of the DAV White Dwarf G 226--29

Abstract

We observed G 226-29 for 15 hours with the HST and detected two problems in spectrograms obtained with the post-COSTAR Faint Object Spectrograph and the G160L grating. First, using the 1 arcsec entrance aperture with a triple peakup, we found a strong ( =~ 3 %) modulation of the total count rate on a time scale similar to the HST orbital period. Second, when comparing the observed spectrum to a spectrum of the same white dwarf obtained with IUE and to model atmospheres for DA white dwarfs, we found 25 % extra flux in the FOS spectrogram in a 75 Angstroms region just to the blue of 1500 Angstroms, due to a scratch in the photocathode, not corrected by the flat-field.