{
  "id": "1505.07112",
  "version": "v1",
  "published": "2015-05-26T20:00:30.000Z",
  "updated": "2015-05-26T20:00:30.000Z",
  "title": "A NuSTAR observation of disk reflection from close to the neutron star in 4U 1608-52",
  "authors": [
    "N. Degenaar",
    "J. M. Miller",
    "D. Chakrabarty",
    "F. Harrison",
    "E. Kara",
    "A. C. Fabian"
  ],
  "comment": "5 pages, 4 figures, 1 table, MNRAS Letters in press",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "Studying the reflection of X-rays off the inner edge of the accretion disk in a neutron star low-mass X-ray binary, allows us to investigate the accretion geometry and to constrain the radius of the neutron star. We report on a NuSTAR observation of 4U 1608-52 obtained during a faint outburst in 2014 when the neutron star, which has a known spin frequency of 620 Hz, was accreting at ~1-2% of the Eddington limit. The 3-79 keV continuum emission was dominated by a Gamma~2 power law, with a ~1-2% contribution from a kTbb~0.3-0.6 keV black body component. The high-quality NuSTAR spectrum reveals the hallmarks of disk reflection; a broad iron line peaking near 7~keV and a Compton back-scattering hump around ~20-30 keV. Modeling the disk reflection spectrum points to a binary inclination of i~30-40 degrees and a small `coronal' height of h<8.5 GM/c2. Furthermore, our spectral analysis suggests that the inner disk radius extended to Rin~7-10 GM/c2, close to the innermost stable circular obit. This constrains the neutron star radius to R<21 km and the redshift from the stellar surface to z>0.12, for a mass of M=1.5 Msun and a spin parameter of a=0.29.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2015-05-26T20:00:30.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "nustar observation",
      "neutron star low-mass x-ray binary",
      "kev black body component",
      "disk reflection spectrum points",
      "kev continuum emission"
    ],
    "publication": {
      "doi": "10.1093/mnrasl/slv072"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 5,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1373264
    }
  }
}