ASCA observations of OAO 1657−415 and its dust-scattered X-ray halo |
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| Authors: | Michael D Audley † Fumiaki Nagase Kazuhisa Mitsuda Lorella Angelini Richard L Kelley |
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| Institution: | UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ;Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan;NASA/Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA;Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA |
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| Abstract: | We report on two ASCA observations of the high-mass X-ray binary pulsar OAO 1657?415. A short observation near mid-eclipse caught the source in a low-intensity state, with a weak continuum and iron emission dominated by the 6.4-keV fluorescent line. A later, longer observation found the source in a high-intensity state and covered the uneclipsed through mid-eclipse phases. In the high-intensity state, the non-eclipse spectrum has an absorbed continuum component due to scattering by material near the pulsar and 80 per cent of the fluorescent iron emission comes from less than 19 light-second away from the pulsar. We find a dust-scattered X-ray halo whose intensity decays through the eclipse. We use this halo to estimate the distance to the source as 7.1 ± 1.3 kpc. |
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| Keywords: | dust extinction X-rays: binaries X-rays: individual: OAO 1657?415 X-rays: ISM |
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