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We present an analysis of chandra/LETGS observations of the ultracompact X-ray binary (UCXB) 4U 1626$-$67, continuing our project to analyze the existing Chandra gratings data of this interesting source. The extremely low mass, hydrogen-depleted donor star provides a unique opportunity to study the properties and structure of the metal-rich accreted plasma. There are strong, double-peaked emission features of OVII-VIII and Ne IX-X, but no other identified emission lines are detected. Our spectral fit simultaneously models the emission line profiles and the plasma parameters, using a two-temperature collisionally-ionized plasma. Based on our line profile fitting, we constrain the inclination of the system to 25--60$^{circ}$ and the inner disk radius to $sim$1500 gravitational radii, in turn constraining the donor mass to $lesssim$0.026 M_sun, while our plasma modeling confirms previous reports of high neon abundance in the source, establishing a Ne/O ratio in the system of $0.47 pm 0.04$, while simultaneously estimating a very low Fe/O ratio of $0.0042 pm 0.0008$ and limiting the Mg/O ratio to less than 1% by number. We discuss these results in light of previous work.
We report on high-resolution X-ray spectroscopy of the ultracompact X-ray binary pulsar 4U 1626-67 with Chandra/HETGS acquired in 2010, two years after the pulsar experienced a torque reversal. The well-known strong Ne and O emission lines with Keple
We present an analysis of the spectral shape and pulse profile of the accretion-powered pulsar 4U 1626-67 observed with Suzaku and NuSTAR during a spin-up state. The pulsar, which experienced a torque reversal to spin-up in 2008, has a spin period of
We present analysis of 4U 1626-67, a 7.7 s pulsar in a low-mass X-ray binary system, observed with the hard X-ray detector of the Japanese X-ray satellite Suzaku in March 2006 for a net exposure of sim88 ks. The source was detected at an average 10-6
Recent X-ray observations by Fermi/GBM discovered a new torque reversal of 4U 1626-67 after 18 years of steady spinning down. Using Swift/BAT observations we were able to center this new torque reversal on Feb 4 2008, lasting approximately 150 days.
After about 18 years of steadily spinning down, the accretion-powered pulsar 4U 1626-67, experienced a torque reversal at the beginning of 2008. For the present study we have used all available Fermi/GBM data since its launch in 2008 June 11 and over