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Astron. Astrophys. 324, L9-L12 (1997)

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Letter to the Editor

The complex X-ray spectrum of the low-mass X-ray binary 4U 1626-67

Alan Owens , T. Oosterbroek and A.N. Parmar

1 Astrophysics Division, Space Science Department of ESA, ESTEC, P.O. Box 299, 2200 AG Noordwijk, Netherlands

Received 13 May 1997 / Accepted 30 May 1997


We report on observations of the X-ray pulsar 4U 1626-67 by the LECS instrument on-board BeppoSAX. We confirm the recent ASCA discovery of excess emission near 1 keV (Angelini et al. 1995). The pulse period of 7.66794 [FORMULA] 0.00004 s indicates that the source continues to spin-down. The phase averaged spectrum is well fit by an absorbed power-law of photon index 0.61 [FORMULA] 0.02 and a blackbody of temperature 0.33 [FORMULA] 0.02 keV, together with an emission feature at 1.05 [FORMULA] 0.02 keV. This spectral shape is similar to that observed by ASCA during the spin-down phase, but significantly different from measurements during spin-up. This suggests that the change in spectrum observed by ASCA may be a stable feature during spin-down intervals. The source intensity is a factor [FORMULA] 2 lower than observed by ASCA three years earlier, confirming that 4U 1626-67 continues to become fainter with time.

Key words: stars: - individual: (4U 1626-67) - stars: neutron - X-rays: stars -stars: binaries: close

Send offprint requests to: A. Owens: aowens@astro.estec.esa.nl

© European Southern Observatory (ESO) 1997

Online publication: May 26, 1998