HST-Study of Changes in the White Dwarf Component of the Most Extreme Dwarf Nova WZ Sagittae Following its Giagantic, Unexpected July 2001 Outburst
WZ Sge, the most extreme dwarf nova and, at 43 pc, one of the closest known cataclysmic variables has an orbital period of only 81.6 minutes, one of the shortest known for any binary star. It has the largest outburst amplitude (7.5mag), longest interoutburst interval (33yr), longest duration outburst (~4 months) of any dwarf novae. The system undergoes hot spot (not white dwarf) eclipses and the inclination (75 degrees) is known to within 4-5 degrees. WZ Sge unexpectedly went into outburst on July 23, 2001, 10 years earlier than expected. The decline has taken more than 3 yrs during which outburst-related material along the line of sight has gradually diminished. We present the results of our most recent HST STIS observations of the accreting white dwarf whose chemical abundances, rotation and temperature variations with time bear the imprint of this extraordinary gigantic accretion event. We discuss the white dwarf rotation rate which is critical to understanding whether the mysterious 28s oscillations are due to rotation or pulsation.
|Other Authors:||Patrick Godon, Edward Sion, Fuhua Cheng, Paula Szkody, K. S. Long, B. T. Gaensicke|