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Title: NuSTAR discovery of a cyclotron line in the Be/X-ray binary RX J0520.5–6932 during outburst

We present spectral and timing analysis of NuSTAR observations of RX J0520.5–6932 in the 3-79 keV band collected during its outburst in 2014 January. The target was observed on two epochs and we report the detection of a cyclotron resonant scattering feature with central energies of E{sub CRSF}=31.3{sub −0.7}{sup +0.8} keV and 31.5{sub −0.6}{sup +0.7} keV during the two observations, respectively, corresponding to a magnetic field of B ≈ 2 × 10{sup 12} G. The 3-79 keV luminosity of the system during the two epochs, assuming a nominal distance of 50 kpc, was 3.667 ± 0.007 × 10{sup 38} erg s{sup –1} and 3.983 ± 0.007 × 10{sup 38} erg s{sup –1}. Both values are much higher than the critical luminosity of ≈1.5 × 10{sup 37} erg s{sup –1}, above which a radiation-dominated shock front may be expected. This adds a new object to the sparse set of three systems that have a cyclotron line observed at luminosities in excess of 10{sup 38} erg s{sup –1}. A broad (σ ≈ 0.45 keV) Fe emission line is observed in the spectrum at a central energy of 6.58{sub −0.05}{sup +0.05} keV in both epochs. The pulse profile of the pulsar was observedmore » to be highly asymmetric with a sharply rising and slowly falling profile of the primary peak. We also observed minor variations in the cyclotron line energy and width as a function of the rotation phase.« less
Authors:
; ; ;  [1] ;  [2] ;  [3] ;  [4] ; ;  [5] ;  [6] ; ;  [7] ;  [8] ;  [9]
  1. Space Radiation Laboratory, California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, CA 91125 (United States)
  2. Center for Research and Exploration in Space Science and Technology, University of Maryland, Baltimore County, Baltimore, MD 21250 (United States)
  3. Université de Toulouse, UPS-OMP, IRAP, F-31400 Toulouse (France)
  4. Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune University Campus, Pune 411007 (India)
  5. Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)
  6. DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark)
  7. Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States)
  8. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)
  9. NASA Goddard Space Flight Center, Astrophysics Science Division, Code 661, Greenbelt, MD 20771 (United States)
Publication Date:
OSTI Identifier:
22370019
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 795; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; ASYMMETRY; CYCLOTRON RADIATION; DETECTION; DISTANCE; EMISSION; KEV RANGE; LUMINOSITY; MAGNETIC FIELDS; NEUTRONS; PULSARS; RESONANCE SCATTERING; ROTATION; SPECTRA; STARS; X RADIATION