2015•Monthly Notices of the Royal Astronomical SocietyOpen access
NuSTAR detection of a cyclotron line in the supergiant fast X-ray transient IGR J17544−2619
V. Bhalerao, Patrizia Romano, John A. Tomsick, L. Natalucci, David M. Smith, Eric C. Bellm, Steven E. Boggs, Deepto Chakrabarty, Finn E. Christensen, William W. Craig, Felix S. Fürst, Charles J. Hailey, Fiona A. Harrison, Roman Krivonos, Ting-Ni Lu, Kristin Kruse Madsen, Daniel K. Stern, George A. Younes, William Zhang
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Abstract
We present NuSTAR spectral and timing studies of the Supergiant Fast X-ray Transient (SFXT) IGR J17544-2619. The spectrum is well-described by a ~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 a SFXT. The inferred magnetic field strength, B = (1.45 +/- 0.03) * 10^12 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.
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