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    • Keywords

       

      Stars: neutron; pulsars: individual: OAO 1657-415; X-rays: stars.

    • Abstract

       

      We present the results obtained from analysis of two AstroSat observations of the high mass Xray binary pulsar OAO 1657-415. The observations covered 0.681–0.818 and 0.808–0.968 phases of the $\sim$10.4 day orbital period of the system, in March and July 2019, respectively. Despite being outside theeclipsing regime, the power density spectrum from the first observation lacks any signature of pulsation or quasi-periodic oscillations. However, during July observation, X-ray pulsations at a period of 37.0375 s were clearly detected in the light curves. The pulse profiles from the second observation consist of a broad single peak with a dip-like structure in the middle across the observed energy range. We explored evolution of the pulse profile in narrow time and energy segments. We detected pulsations in the light curves obtained from0.808–0.92 orbital phase range, which is absent in the remaining part of the observation. The spectrum of OAO 1657-415 can be described by an absorbed power-law model along with an iron fluorescent emission line and a blackbody component for out-of-eclipse phase of the observation. Our findings are discussed in the frame of stellar wind accretion and accretion wake at late orbital phases of the binary.

    • Author Affiliations

       

      GAURAVA K. JAISAWAL1 SACHINDRA NAIK2 PRAHLAD R. EPILI3 BIRENDRA CHHOTARAY2 4 ARGHAJIT JANA2 P. C. AGRAWAL5

      1. National Space Institute, Technical University of Denmark, Elektrovej 327-328, 2800 Lyngby, Denmark.
      2. Astronomy and Astrophysics Division, Physical Research Laboratory, Navrangapura, Ahmedabad 380 009, India
      3. School of Physics and Technology, Wuhan University, Wuhan 430072, China.
      4. Indian Institute of Technology, Gandhinagar 382 355, India.
      5. Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Colaba, Mumbai 400 005, India.
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