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Preprint E/01

Discovery of a Cyclotron Resonance Scattering Feature in the X-Ray Spectrum of XTE J1946+274

Heindl, W. A. (1); Coburn, W. (1); Gruber, D. E. (1); Rothschild, R. E. (1); Kreykenbohm, I. (2); Wilms, J. (2); Staubert, R. (2)

(1) Center for Astrophysics and Space Sciences, Code 0424, 9500 Gilman Drive, University of California, San Diego, La Jolla, CA 92093-0424
(2) Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Sand 1, D-72076 Tübingen, Germany

2001, ApJ 563, L35

Abstract. Observations made with the Rossi X-Ray Timing Explorer during the course of the 1998 September-November outburst of the transient accreting pulsar XTE J1946+274 reveal a cyclotron resonance scattering feature (or "cyclotron line") in the hard X-ray spectrum near 35 keV. We determine a centroid energy of 36.2^+0.5_-0.7 keV, which implies a magnetic field strength of 3.1(1+z)×10¹² G, where z is the gravitational redshift of the scattering region. The optical depth, tau=0.33^+0.07_-0.06, and width, σ=3.37^+0.92_-0.75 keV, are typical of known cyclotron lines in other pulsars. This discovery makes XTE J1946+274 one of 13 pulsars with securely detected cyclotron lines resulting in direct magnetic field measurements.

Key words: Stars: Individual: Alphanumeric: XTE J1946+274 - Stars: Magnetic Fields - Stars: Neutron - X-Rays: Binaries - X-Rays: Stars

ADS entry

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