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Gamma-ray emission from pulsars: strength of the acceleration field in the outer gap |
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| Authors: | Kouichi Hirotani |
| Institution: | Astronomisches Institut der Universität Erlangen-Nürnberg, Sternwartstrasse 7, D-96049 Bamberg, Germany; Astronomickýústav Slovenskej akadémie vied, SK-05960 TatranskáLomnica, Slovakia; Astronomical Observatory, Volgina 7, 11050 Belgrade, Yugoslavia; Carter Observatory, PO Box 2909, Wellington 1, New Zealand; Section of Astrophysics, Astronomy and Mechanics, Department of Physics, University of Athens, 157 83 Athens, Greece; Astronomical Institute, National Observatory of Athens, 118 10 Athens, Greece |
| Abstract: | In this study we present and re-analyse the historical, 1889–1998, light curve (LC) of the eclipsing symbiotic binary AR Pav. For the first time, we show that the timing of mid-points of eclipses observed during a quiescent phase obeys a quadratic ephemeris, with an initial orbital period P We determined a distance to the system of 5.8±1.5 kpc, the mass ratio of the giant to the hot star, M During quiescence, the LC has characteristic features similar to those observed in cataclysmic variables (CVs). It can be well reproduced by a model of a large accretion disc surrounding the hot star. However, it is probable that the geometry of the transferred material in the Roche lobe of the accretor in AR Pav is different from that of CVs. During active phases the shape of the LC changes considerably. A complex wave-like variation developed as a function of the orbital phase with an amplitude of ～1 mag. It is interpreted in terms of a collisionally heated emission region located on the giant surface and arising from the hot star eruption. |
| Keywords: | binaries: eclipsing binaries: symbiotic stars: fundamental parameters stars: individual: AR Pav |