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Timing and broad-band spectroscopy of 1A 1118-61 with Suzaku

Maitra, Chandreyee and Paul, Biswajit and Naik, Sachindra (2012) Timing and broad-band spectroscopy of 1A 1118-61 with Suzaku. In: Monthly Notices of the Royal Astronomical Society, 420 (3). pp. 2307-2317.

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Official URL: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-...


We present a timing and broad-band pulse-phase-resolved spectral analysis of the transient Be X-ray binary pulsar 1A 1118-61 observed during its outburst in 2009 January using Suzaku observations. The Suzaku observations were made twice, once at the peak of the outburst, and the other 13 d later at its declining phase. Pulse profiles from both observations exhibit strong energy dependence with several peaks at low energies and a single peak above similar to 10 keV. A weak, narrow peak is detected at the main dip of the pulse profiles from both observations in the energy bands below 3 keV, indicating the presence of a phase-dependent soft excess in the source continuum. The broad-band energy spectrum of the pulsar could be fitted well with a partial covering cut-off power-law model and a narrow iron fluorescence line. We also detect a broad cyclotron feature at similar to 50 keV from both observations which is a feature common for accretion-powered pulsars with high magnetic field strength. The pulse-phase-resolved spectral analysis shows an increase in the absorption column density of the partial covering component, as well as variation in the covering fraction at the dips of the pulse profiles, which naturally explains energy dependence of the same. The cyclotron line parameters also show significant variation with pulse phase with an similar to 10 keV variation in the cyclotron line energy and a variation in depth by a factor of 3. This can be explained either as the effect of different viewing angles of the dipole field at different pulse phases, or due to a more complex underlying magnetic field geometry.

Item Type: Journal Article
Publication: Monthly Notices of the Royal Astronomical Society
Publisher: John Wiley and Sons
Additional Information: Copyright of this article belongs to John Wiley and Sons.
Keywords: pulsars:general;X-rays:binaries;X-rays:individual:1A 1118-61
Department/Centre: Division of Physical & Mathematical Sciences > Joint Astronomy Programme
Date Deposited: 28 Mar 2012 05:23
Last Modified: 28 Mar 2012 05:23
URI: http://eprints.iisc.ac.in/id/eprint/44086

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