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Astron. Astrophys. 342, L45-L48 (1999)

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Letter to the Editor

Evidence for a brown dwarf in the TOAD V592 Herculis *

A. van Teeseling 1, F.V. Hessman 1 and R.W. Romani 1,2

1 Universitäts-Sternwarte Göttingen, Geismarlandstrasse 11, D-37083 Göttingen, Germany
2 Department of Physics, M.C. 4060, Stanford, CA 94350, USA

Received 15 December 1998 / Accepted 12 January 1999


We present optical R and I photometry of V592 Her obtained one year before its 1998 outburst. We identify V592 Her with a faint blue star, showing variability in R with a standard deviation of [FORMULA] mag. With mean quiescent magnitudes of [FORMULA] and [FORMULA], its outburst amplitude is [FORMULA] mag, which is at the very upper end of the range observed for Tremendous-Outburst-Amplitude Dwarf novae. A main sequence secondary would imply a distance [FORMULA] pc, which is inconsistent with the absolute magnitudes in outburst and quiescence expected for a dwarf nova. We conclude that the secondary is a brown dwarf. The quiescent flux is almost completely from the white dwarf, which gives a white dwarf temperature of [FORMULA] K and a distance of [FORMULA] pc. The non-detection in a ROSAT PSPC observation implies an upper limit to the X-ray luminosity of [FORMULA] erg s-1 and to the accretion rate onto the white dwarf of [FORMULA].

Key words: accretion, accretion disks – stars: individual: V592 Her – stars: low-mass, brown dwarfs – stars: novae, cataclysmic variables – X-rays: stars

* Based on observations collected at McDonald Observatory, Texas

© European Southern Observatory (ESO) 1999

Online publication: February 23, 1999