Hubble Space Telescope Fine Guidance Sensor astrometric parallaxes for 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 fou nd a parallax for SS Aurigae of pi = 5.00 +/- 0.64 mas, for SS Cygni we fou nd pi = 6.02 +/- 0.46 mas, and for U Geminorum we obtained pi = 10.37 +/- 0 .50 mas. These represent the first true trigonometric parallaxes of any dwa rf 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-milliarcse cond precision.