NuSTAR discovery of a cyclotron line in the Be/X-ray binary RX J0520.5–6932 during outburst
- Space Radiation Laboratory, California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, CA 91125 (United States)
- Center for Research and Exploration in Space Science and Technology, University of Maryland, Baltimore County, Baltimore, MD 21250 (United States)
- Université de Toulouse, UPS-OMP, IRAP, F-31400 Toulouse (France)
- Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune University Campus, Pune 411007 (India)
- Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)
- DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark)
- Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States)
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)
- NASA Goddard Space Flight Center, Astrophysics Science Division, Code 661, Greenbelt, MD 20771 (United States)
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 observed 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.
- OSTI ID:
- 22370019
- Journal Information:
- Astrophysical Journal, Vol. 795, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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