ART-P/Granat observations of the X-ray pulsar 4U0115+634 during the outburst in February 1990 |
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| Authors: | A A Lutovinov S A Grebenev R A Sunyaev |
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| Institution: | (1) Space Research Institute, Russian Academy of Sciences, ul. Profsoyuznaya 84/32, Moscow, 117810, Russia;(2) Max-Planck Institut für Astrophysik, Garching, Germany |
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| Abstract: | Observations of the transient X-ray pulsar 4U0115+634 with the ART-P telescope aboard the Granat Observatory during the outburst in February 1990 are presented. The source exhibited a strong, regular and irregular variability, including X-ray bursts of duration 300–500 s. Two absorption features were detected in the source's photon spectrum at ～12 and ～22 keV, which were interpreted as the lines of resonance scattering of its emission at the first and second cyclotron harmonics. The magnetic-field strength B on the neutron-star surface that corresponds to these lines is ～1.3 × 1012 G. The ratio of the line energies slightly differs from the harmonic ratio 1: 2. Moreover, this ratio and the line energies themselves vary appreciably with phase on a time scale of one pulsation period. The dependence of other spectral parameters for 4U0115+634 on pulse phase is investigated. |
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