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Astron. Astrophys. 323, L41-L44 (1997)

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Letter to the Editor

RX J0439.8-6809: a double-degenerate supersoft X-ray source? *

A. van Teeseling , K. Reinsch , F.V. Hessman and K. Beuermann

Universitäts-Sternwarte Göttingen, Geismarlandstr. 11, D-37083 Göttingen, Germany

Received 27 February 1997 / Accepted 15 May 1997


We present optical CCD photometry of the supersoft X-ray source RX J0439.8-6809. The absence of significant X-ray and optical variability ([FORMULA] peak-to-peak [FORMULA]) and the optical faintness ([FORMULA]) put severe constraints on a possible binary nature. Without rather unusual assumptions, a main-sequence donor star seems to be ruled out. All of the available information suggests that RX J0439 is either a double-degenerate supersoft X-ray source with a predicted orbital period of a few minutes or an extremely hot single pre-white dwarf. In either case, it is an extraordinarily rare and interesting object.

Key words: accretion – stars: individual: RX J0439.8-6809 – stars: post-AGB – white dwarfs – X-rays: stars

* Based in part on observations collected at the European Southern Observatory, La Silla, Chile: ESO [FORMULA] 58.D-0275

SIMBAD Objects


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© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998