BeppoSAX observation of the eclipsing dipping X-ray binary X 1658-298

¹ Astrophysics Division, Space Science Department of ESA, ESTEC, PO Box 299, 2200 AG Noordwijk, The Netherlands
² Astronomical Institute, Utrecht University, PO Box 80 000, 3508 TA Utrecht, The Netherlands
³ Space Research Organization Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands

Corresponding author: T. Oosterbroek, toosterb@astro.estec.esa.nl

Received: 8 January 2001
Accepted: 5 July 2001

Abstract

Results of a 2000 August 12-13 BeppoSAX observation of the 7.1 hr eclipsing, dipping, bursting, transient, low-mass X-ray binary (LMXRB) X 1658-298 are presented. The spectrum outside of eclipses, dips and bursts can be modeled by the combination of a soft disk-blackbody and a harder Comptonized component with a small amount atom cm^-2) of low-energy absorption. In contrast, an RXTE observation 18 months earlier during the same outburst, measured an absorption of atom cm^-2. Such a change is consistent with a thinning of the accretion disk as the outburst progresses. Structured residuals from the best-fit spectral model are present which are tentatively identified with Ne-K/Fe-L and Fe-K shell emission. The spectral changes during dips are complex and may be modeled by a strong (~ atom cm^-2) increase in absorption of the Comptonized component only, together with reductions in normalizations of both spectral components. This behavior is in contrast to the "complex continuum" model for X-ray dip sources, where the softer blackbody component rapidly suffers strong absorption. It is however, similar to that found during recent XMM-Newton observations of the eclipsing, dipping, LMXRB EXO 0748-676. An updated orbital ephemeris is provided which does not require a quadratic term, in contrast to that of Wachter et al. ([CITE]).