NuSTAR detection of a cyclotron line in the supergiant fast X-ray transient IGR J17544-2619

• Main Authors: Bhalerao, Varun (Author), Romano, Patrizia (Author), Tomsick, John (Author), Natalucci, Lorenzo (Author), Smith, David M. (Author), Bellm, Eric (Author), Boggs, Steven E. (Author), Chakrabarty, Deepto (Contributor), Christensen, Finn E. (Author), Craig, William W. (Author), Fuerst, Felix (Author), Hailey, Charles J. (Author), Harrison, Fiona A. (Author), Krivonos, Roman A. (Author), Lu, Ting-Ni (Author), Madsen, Kristin K. (Author), Stern, Daniel (Author), Younes, George (Author), Zhang, William (Author)
• Other Authors: Massachusetts Institute of Technology. Department of Physics (Contributor)
• Format: Article
• Language: English
• Published: Oxford University Press, 2015-08-06T12:07:14Z.
• Subjects: Article
• Online Access: Get fulltext

We present NuSTAR spectral and timing studies of the supergiant fast X-ray transient (SFXT) IGR J17544−2619. The spectrum is well described by an ~1 keV blackbody and a hard continuum component, as expected from an accreting X-ray pulsar. We detect a cyclotron line at 17 keV, confirming that the compact object in IGR J17544−2619 is indeed a neutron star. This is the first measurement of the magnetic field in an SFXT. The inferred magnetic field strength, B = (1.45 ± 0.03) × 10[superscript 12]G (1 + z) is typical of neutron stars in X-ray binaries, and rules out a magnetar nature for the compact object. We do not find any significant pulsations in the source on time-scales of 1-2000 s.
United States. National Aeronautics and Space Administration (Contract NNG08FD60C)