[ITAL]Hubble Space Telescope[/ITAL] Fine Guidance Sensor Astrometric Parallaxesfor Three Dwarf Novae: SS Aurigae, SS Cygni, and U Geminorum

We report astrometric parallaxes for three well-known dwarf novae obtained using the Fine Guidance Sensors on the Hubble Space Telescope ( HST ). We found a parallax for SS Aurigae of π=5.00±0.64 mas, for SS Cygni we found π=6.02±0.46 mas, and for U Geminorum we obtained π=10.37±0.50 mas. These represent the first true trigonometric parallaxes of any dwarf novae. We briefly compare these results with previous distance estimates. This program demonstrates that with a very modest amount of HST observing time, the Fine Guidance Sensors can deliver parallaxes with sub-milliarcsecond precision.