AnHSTparallax of the distant cataclysmic variable V1223 Sgr, its system parameters, and accretion rate

Abstract

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 πabs = 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 MV = 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 Lacc = (2.6 ± 0.8) × 10 34 erg s −1 , a white dwarf mass M1 = 0.93 ± 0.12 M� , and an accretion rate u M = (1.4 ± 0.3) × 10 17 gs −1 ,