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

A. Owens·T. Oosterbroek·A. N. Parmar
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Abstract

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 +/- 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 +/- 0.02 and a blackbody of temperature 0.33 +/- 0.02 keV, together with an emission feature at 1.05 +/- 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 ~2 lower than observed by ASCA three years earlier, confirming that 4U 1626-67 continues to become fainter with time.

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A. Owens, T. Oosterbroek, A. N. Parmar. 1997-06-03. The complex X-ray spectrum of the low-mass X-ray binary 4U 1626-67. https://arxiv.org/abs/astro-ph/9706021

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