A torque reversal to spin-up in 4U 1626-67

Abstract

We report the detection of a recent torque reversal to spin-up in 4U 1626-67. This is an accretion powered X-ray pulsar and shows slow gradual intensity and pulse period variation on a few years of timescale. Recently, a significant increase in the X-ray flux was observed in the long term RXTE-ASM and Swift-BAT light curve (Krimm et al. 2008, ATel #1426, 1, Jain et al. 2009, astro-ph 0906.4169) around MJD 54500.