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

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

Abstract

We present optical CCD photometry of the supersoft X-ray source RX J0439.8-6809. The absence of significant X-ray and optical variability ( peak-to-peak ) and the optical faintness () 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 58.D-0275

© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998

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