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

¹ Universitäts-Sternwarte Göttingen, Geismarlandstr. 11, 37083 Göttingen, Germany
² New Mexico State University, Box 30001/MSC 4500, Las Cruces 88003, Mexico e-mail: tharriso@nmsu.edu
³ McDonald Observatory, University of Texas, Austin, 78712 Texas, USA e-mail: mca@barney.as.utexas.edu; fritz@astro.as.utexas.edu
⁴ Department of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ, UK e-mail: btg@astro.soton.ac.uk

Received: 1 October 2003
Accepted: 10 February 2004

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  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 . 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  erg s^-1, a white dwarf mass  , and an accretion rate  g s^-1,