* Astronomy

Title: Suzaku Observations of the Ultracompact binary System 4U 1626-67
Authors: Ascension Camero-Arranz, Katja Pottschmidt, Mark Finger, C.A. Wilson-Hodge, D. M. Marcu

The accretion-powered pulsar 4U 1626-67 experienced a new torque reversal at the beginning of 2008, after about 18 years of steadily spinning down. We present a spectral analysis of this source using two pointed observations performed by Suzaku in 2006 March and in 2010 September. We confirm with Suzaku the presence of a strong emission-line complex centred on 1 keV, with the strongest line being the hydrogen-like Ne Ly{\alpha} at 1.025(1.5) keV. We were able to resolve this complex with up to eight emission lines. A dramatic increase of the equivalent width of the Ne Ly{\alpha} 1.021 keV after the 2008 torque reversal occurred, reaching almost the same value measured by ASCA in 1993. In addition, we confirm the general decrease trend of the equivalent widths during the spin-down period. We also report on the detection of a cyclotron line feature centred at ~37 keV. In spite of the fact that a dramatic increase of the X-ray luminosity (0.5-100 keV) of a factor of ~3.5 occurred between these two observations, no significant change in the energy of the cyclotron line feature was observed. However, the intensity of the ~1 keV line complex increased by an overall factor of ~10.

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