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Astron. Astrophys. 338, L13-L16 (1998)

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Letter to the Editor

The transient jet of the galactic supersoft X-ray source RX J0925.7-4758 *

C. Motch

Observatoire Astronomique, UMR 7550 CNRS, 11 rue de l'Université, F-67000 Strasbourg, France

Received 29 June 1998 / Accepted 23 July 1998


We report the discovery of a transient jet in the supersoft X-ray source RX J0925.7-4758. The jet was observed in the H[FORMULA] line during a single night in June 1997 and had disappeared one day later. RX J0925.7-4758 is the third supersoft source to exhibit collimated outflows. The peak jet velocity of 5,200 km s-1, strongly argues in favour of a white dwarf in RX J0925.7-4758. Simple modelling of the jet profile suggests half opening angles in the range of [FORMULA] to [FORMULA] although the outflow may be narrower if part of the observed spread in velocity is intrinsic to the jet. X-ray spectral modelling (Ebisawa et al. 1996; Hartmann & Heise 1997) indicates distances of the order of 10 kpc or more with the consequence that RX J0925.7-4758 may be the most optically luminous supersoft source known. The overall observational picture points to a massive white dwarf which may be close to the Chandrasekhar limit.

Key words: X-ray: stars – stars: white dwarfs – stars: binaries: close – stars: mass-loss – stars: individual: RX J0925.7-4758

* Based on observations obtained at the European Southern Observatory, La Silla (Chile) with the ESO-Danish telescope

Send offprint requests to: C. Motch

© European Southern Observatory (ESO) 1998

Online publication: September 8, 1998