1RXS J180408.9-342058 is a transient neutron star low-mass X-ray binary that exhibited a bright accretion outburst in 2015. We present Nustar, Swift, and Chandra observations obtained around the peak of this outburst. The source was in a soft X-ray spectral state and displayed an X-ray luminosity of Lx~(2-3)E37 (D/5.8 kpc)^2 erg cm-2 (0.5-10 keV). The Nustar data reveal a broad Fe-K emission line that we model as relativistically broadened reflection to constrain the accretion geometry. We found that the accretion disk is viewed at an inclination of i~27-35 degrees and extended close to the neutron star, down to Rin~5-7.5 gravitational radii (~11-17 km). This inner disk radius suggests that the neutron star magnetic field strength is B<2E8 G. We find a narrow absorption line in the Chandra/HEG data at an energy of ~7.64 keV with a significance of ~4.8 sigma. This feature could correspond to blue-shifted Fe xxvi and arise from an accretion disk wind, which would imply an outflow velocity of v~0.086c (~25800 km s-1). However, this would be extreme for an X-ray binary and it is unclear if a disk wind should be visible at the low inclination angle that we infer from our reflection analysis. Finally, we discuss how the X-ray and optical properties of 1RXS J180408.9-342058 are consistent with a relatively small (Porb<3 hr) binary orbit.
@article{arxiv.1607.01780,
title = {Disk reflection and a possible disk wind during a soft X-ray state in the neutron star low-mass X-ray binary 1RXS J180408.9-342058},
author = {N. Degenaar and D. Altamirano and M. Parker and J. C. A. Miller-Jones and J. M. Miller and C. O. Heinke and R. Wijnands and R. Ludlam and A. Parikh and J. W. T. Hessels and N. Gusinskaia and A. T. Deller and A. C. Fabian},
journal= {arXiv preprint arXiv:1607.01780},
year = {2016}
}
Comments
10 pages, 3 tables, 5 figures, accepted for publication in MNRAS