Transient Be/X-ray binary pulsar EXO 2030+375 at the peak of a normal type I outburst}
Abstract
We present the timing and broad-band spectral properties of the Be transient high mass X-ray binary pulsar EXO 2030+375 using a Suzaku observation during the peak of the 2007 May-June outburst. Pulsations with a period of 41.41 s were clearly detected in the light curves of the pulsar up to energy ∼100 keV. The pulse profile was found to be strongly energy dependent. Narrow dips which are generally seen in the pulse profiles up to ∼10 keV, are found to be present in the profiles up to as high as ∼70 keV. At high energies, these dips gradually disappeared and the pulse profile appeared as single-peaked. The broad-band spectrum of the pulsar in 1.0-200.0 keV energy range is found to be well described by a partial covering power-law with high energy cut-off continuum model. Several emission lines such as Si, S, Fe are also detected in the pulsar spectrum. We attempted to fit the spectrum using neutral as well as partially ionized absorbers along with the above continuum models yielding similar results. The spectral fitting, however, did not require any Cyclotron Resonance Scattering Feature (CRSF) in the best fit model. To understand the changes in model parameters during the dips in the pulse profile, we carried out pulse phase resolved spectroscopy using data from XIS and PIN. During the dips in the pulse profiles, the value of additional column density was estimated to be high compared to that during the other pulse phases. While using partially ionized absorber, the value of ionization parameter is also higher at the dips in the pulse profiles. This may be the possible reason for the presence of dips up to higher energies.
- Publication:
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Astronomical Society of India Conference Series
- Pub Date:
- 2013
- Bibcode:
- 2013ASInC...9...84N