Title:	Timing and spectral studies of the transient x-ray pulsar GX 304-1 during an outburst
Authors:	Devasia, Jincy James, Marykutty Paul, Biswajit Indulekha, Kavila
Keywords:	binaries: general pulsars: individual GX 304-1 X-rays binaries X-rays: individual: GX 304-1 X-rays: stars X-rays: stars
Issue Date:	Oct-2011
Publisher:	Wiley Interscience for the RAS
Citation:	Monthly Notices of the Royal Astronomical Society, 2011, Vol.417, p348
Abstract:	We present the timing and spectral properties of the transient X-ray pulsarGX304−1 during its recent outburst in 2010 August, using observations carried out with the Proportional Counter Array (PCA) instrument on board the Rossi X-ray Timing Explorer (RXTE) satellite. We detected strong intensity- and energy-dependent variations in the pulse profiles during the outburst. The pulse profile showed significant evolution over the outburst. It showed complex structures consisting of a main peak with steps on both sides during the start of the outburst.On some days, a sharp dip-like feature was seen which disappeared at the end of the outburst when the profile evolved into a sinusoidal shape. At low energies, the pulse profiles appeared complex, consisting of multiple peaks and a narrow minimum. The amplitude of the second brightest peak in low energies decreased with energy, and above 12 keV the shape of the pulse profile changed to a single broad peak with a dip-like feature. The dip had energy dependence, both in phase and in width. We detected quasi-periodic oscillations (QPOs) at 0.125 Hz with a harmonic. The QPO feature had a low rms value of 2.9 per cent and it showed a positive energy dependence up to 40 keV with the rms value increasing to 9 per cent at 40 keV. The QPO frequency decreased from 0.128 to 0.108 Hz in 12 days. During most of the outburst, the 3–30 keV spectrum of GX 304−1 can be well fitted with a partial covering power-law model with a high-energy cut-off and iron fluorescent line emission. For a few of the observations carried out during the decay of the outburst, the partial covering absorption component is found to change to single-component absorption. We also found that the partial covering and high-energy cut-off parameters vary significantly with the pulse phase.
Description:	Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)
URI:	http://hdl.handle.net/2289/4108
ISSN:	0035-8711 1365-2966 (Online)
Alternative Location:	http://adsabs.harvard.edu/doi/10.1111/j.1365-2966.2011.19269.x http://arxiv.org/abs/1106.3251 http://dx.doi.org/10.1111/j.1365-2966.2011.19269.x
Copyright:	2011 The authors & the Royal Astronomical Society.
Appears in Collections:	Research Papers (A&A)

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