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

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 K-alpha detected with NuSTAR; NVII, OVII, 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 M-circle dot NS with a spin of a(*) = 0, this is an inner disk radius of <= 22.2 km. We find the inclination of the system to be between 18 degrees and 29 degrees. 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 B <= (0.3-1.0) x 10(9) G at the magnetic poles, though coherent pulsations have not been detected and the source is not identified as a pulsar.