An HST parallax of the distant cataclysmic variable V1223 Sgr, its system parameters, and accretion rate

Using the Hubble space Telescope Fine Guidance Sensor, we have measured the trigonometric parallax of the bright cataclysmic variable 1223 Sgr. The absolute parallax is π_abs= 1.96± 0.18 mas, making V1223 Sgr the most distant CV with a well-determined trigonometric parallax. This distance, a Lutz-Kelker correction, and the previously measured extinction yield an absolute visual high-state magnitude M_V =4.0±0.2. We outline a model, which is consistent with the observed spin-down of the white dwarf and provides for much of the UV/optical emission by reverberation of X-rays. From previous X-ray {and UV/optical} data, we derive {an accretion luminosity L_acc= (2.6±0.8) × 34 erg s^-1}, a white dwarf mass M₁ = 0.93±0.12 M_⊙, and an accretion rate dot M = (1.4±0.3) × 17 g s^-1,

Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with proposal #9230.