NUSTAR AND XMM-NEWTON OBSERVATIONS OF THE NEUTRON STAR X-RAY BINARY 1RXS J180408.9-34205

Abstract

We report on observations of the neutron star (NS) residing in the low-mass X-ray binary 1RXS J180408.9-34205 taken 2015 March by NuSTAR and XMM-Newton while the source was in the hard spectral state. We find multiple reflection features (Fe detected with NuSTAR ; N vii , O vii , and O viii detected in the RGS) from different ionization zones. Through joint fits using the self-consistent relativistic reflection model relxill , we determine the inner radius to be ≤11.1 R g . For a 1.4 NS with a spin of , this is an inner disk radius of km. We find the inclination of the system to be between 18° and 29°. If the disk is truncated at a radius greater than the NS radius, it could be truncated by a boundary layer on the NS surface. It is also possible that the disk is truncated at the magnetospheric radius; conservative estimates would then imply G at the magnetic poles, though coherent pulsations have not been detected and the source is not identified as a pulsar.