Constraints on the mass and radius of the neutron star XTEJ1807-294

Abstract

The accreting millisecond pulsar XTEJ1807-294 is studied through a pulse-shape modeling analysis. The model includes blackbody and Comptonized emission from the one visible hot spot and makes use of the Oblate Schwarzschild approximation for ray-tracing. We include a scattered light contribution, which accounts for flux scattered off an equatorial accretion disk to the observer including time delays in the scattered light. We give limits to mass and radius for XTEJ1807-294 and compare these to limits determined for SAX J1808-3658 and XTEJ1814-334 previously determined using similar methods. The resulting allowed region for mass-radius curves is small but consistent with a mass-radius relation with nearly constant radius (12km) for masses between 1 and 2.5 solar masses. © 2011. The American Astronomical Society. All rights reserved.