Timing and spectral studies of the transient X-ray pulsar GX 304−1 during an outburst

Devasia, Jincy; James, Marykutty; Paul, Biswajit; Indulekha, K.

doi:10.1111/j.1365-2966.2011.19269.x

Cited by 34 publications

(42 citation statements)

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“…Earlier, the evolution of pulse profiles up to ∼30 keV had been reported by using RXT E/PCA observations during 2010 outburst (Devasia et al 2011). Using Suzaku observations, the evolution of pulse profiles up to ∼150 keV has been presented in this paper.…”

Section: Introductionmentioning

confidence: 95%

“…Since then, several X-ray outbursts have been detected in the pulsar with Swift/BAT and M AXI (Yamamoto et al 2009(Yamamoto et al , 2012Krimm et al 2010;Mihara et al 2010). Using the Rossi X-Ray Timing Explorer (RXTE) observations during 2010 August outburst, energy and luminosity dependence of pulse profiles were found in GX 304-1 (Devasia et al 2011). Apart from the evolution of pulse profiles, a quasi-periodic oscillation (QPO) at ∼0.125 Hz was detected with harmonics in several RXT E/PCA observations during this outburst.…”

Section: Introductionmentioning

confidence: 99%

“…Apart from the evolution of pulse profiles, a quasi-periodic oscillation (QPO) at ∼0.125 Hz was detected with harmonics in several RXT E/PCA observations during this outburst. The pulsar spectrum in 3-30 keV range was described with a partial covering high energy cutoff power-law model (Devasia et al 2011). During the same outburst in 2010 August, a cyclotron absorption feature at ∼54 keV was detected in the pulsar spectrum (Yamamoto et al 2011) and the corresponding magnetic field of the neutron star was estimated to be ∼4.7×10 12 G. A positive correlation between cyclotron energy and luminosity was seen during 2012 January-February outburst with INTEGRAL .…”

Section: Introductionmentioning

confidence: 99%

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Suzakuview of the Be/X-ray binary pulsar GX 304-1 during Type I X-ray outbursts

Jaisawal

Naik

Epili

2016

Mon. Not. R. Astron. Soc.

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We report the timing and spectral properties of Be/X-ray binary pulsar GX 304-1 by using two Suzaku observations during its 2010 August and 2012 January X-ray outbursts. Pulsations at ∼275 s were clearly detected in the light curves from both the observations. Pulse profiles were found to be strongly energy-dependent. During 2010 observation, prominent dips seen in soft X-ray ( 10 keV) pulse profiles were found to be absent at higher energies. However, during 2012 observation, the pulse profiles were complex due to the presence of several dips. Significant changes in the shape of the pulse profiles were detected at high energies (>35 keV). A phase shift of ∼0.3 was detected while comparing the phase of main dip in pulse profiles below and above ∼35 keV. Broad-band energy spectrum of pulsar was well described by a partially absorbed Negative and Positive power-law with Exponential cutoff (NPEX) model with 6.4 keV iron line and a cyclotron absorption feature. Energy of cyclotron absorption line was found to be ∼53 and 50 keV for 2010 and 2012 observations, respectively, indicating a marginal positive dependence on source luminosity. Based on the results obtained from phase-resolved spectroscopy, the absorption dips in the pulse profiles can be interpreted as due to the presence of additional matter at same phases. Observed positive correlation between cyclotron line energy and luminosity, and significant pulse-phase variation of cyclotron parameters are discussed in the perspective of theoretical models on cyclotron absorption line in X-ray pulsars.

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Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Suzakuview of the Be/X-ray binary pulsar GX 304-1 during Type I X-ray outbursts

Jaisawal

Naik

Epili

2016

Mon. Not. R. Astron. Soc.

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“…html cyclotron line energy with flux. Spectral and/or timing studies covering most of the same giant outbursts analysed in this work have also been performed for the following sources: V0332+53 (Tsygankov et al 2010;Nakajima et al 2010), KS 1947+300 (Galloway et al 2004), EXO 2030+375 (Wilson et al 2008), 1A 1118-616 (Nespoli & Reig 2011Devasia et al 2011), 1A 0535+262 (Acciari et al 2011), XTE J0658-073 (McBride at al. 2006Nespoli et al 2012), GRO J1008-57 (Naik et al 2011), Swift J1656.6-5156 (Içdem et al 2011;Reig et al 2011).…”

Section: Observationsmentioning

confidence: 99%

Patterns of variability in Be/X-ray pulsars during giant outbursts

Reig

Nespoli

2013

A&A

124

142

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Context. The discovery of source states in the X-ray emission of black-hole binaries and neutron-star low-mass X-ray binaries constituted a major step forward in the understanding of the physics of accretion onto compact objects. While there are numerous studies on the correlated timing and spectral variability of these systems, very little work has been done on high-mass X-ray binaries, the third major type of X-ray binaries. Accretion-powered pulsars with Be companions represent the most numerous group of high-mass X-ray binaries. When active, they are amongst the brightest extra-solar objects in the X-ray sky and are characterised by dramatic variability in brightness on timescales of days. Aims. The main goal of this work is to investigate whether Be accreting X-ray pulsars display source states and characterise those states through their spectral and timing properties. Methods. We have made a systematic study of the power spectra, energy spectra and X-ray hardness-intensity diagrams of nine Be/X-ray pulsars. Energy spectra were fitted with an absorbed power-law modified by an exponential cutoff. Discrete components such as iron emission lines and cyclotron lines were represented by Gaussian and pseudo-Lorentzian profiles, respectively. Power spectra were fitted by a combination of Lorentzian functions. The evolution of the timing and spectral parameters were monitored through changes over two orders of magnitude in luminosity. Results. We find that Be/X-ray pulsars trace two different branches in the hardness-intensity diagram: the horizontal branch corresponds to a low-intensity state of the source and it is characterised by fast colour and spectral changes and high X-ray variability. The diagonal branch is a high-intensity state that emerges when the X-ray luminosity exceeds a critical limit. The photon index anticorrelates with X-ray flux in the horizontal branch but correlates with it in the diagonal branch. The correlation between quasi-periodic oscillation frequency and X-ray flux reported in some pulsars is also observed if the peak frequency of the broad-band noise that accounts for the aperiodic variability is used. In some sources, a significant correlation between spectral and timing parameters is seen, implying and interplay between the accretion column and the inner accretion disc. Conclusions. The two branches may reflect two different accretion modes, depending on whether the luminosity of the source is above or below a critical value. This critical luminosity is mainly determined by the magnetic field strength, hence it differs for different sources. In this work, the systems that display the two branches have critical luminosities in the range (1−4) × 10 37 erg s −1 .

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“…Many neutron star binaries show the opposite behavior with peaks vanishing at high energies, e.g., 4U 0115+634 (Müller et al 2010), 4U 1909+07 (Fürst et al 2011), Vela X-1 (Kreykenbohm et al 2002), GX 304−1 (Devasia et al 2011), 1A 1118−61 Maitra et al 2012), GRO J1008−57 (Naik et al 2011b), or EXO 2030+375 (Naik et al 2013). We note, however, that IGR J16393−4643 shows an evolution with energy that is similar to that in KS 1947+300 (Islam et al 2015).…”

Section: Discussionmentioning

confidence: 68%

Suzakuobservations of the 2013 outburst of KS 1947+300

Ballhausen

Kühnel

Pottschmidt

et al. 2016

A&A

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We report on the timing and spectral analysis of two Suzaku observations with different flux levels of the high-mass X-ray binary KS 1947+300 during its 2013 outburst. In agreement with simultaneous NuSTAR observations, the continuum is well described by an absorbed power law with a cutoff and an additional blackbody component. In addition, we find fluorescent emission from neutral, Helike, and even H-like iron. We determine a pulse period of ∼18.8 s with the source showing a spin-up between the two observations. Both Suzaku observations show very similar behavior of the pulse profile, which is strongly energy dependent. This profile has an evolution from a profile with one peak at low energies to a profile with two peaks of different widths toward higher energies seen in both the Suzaku and NuSTAR data. Such an evolution to a more complex profile at higher energies is rarely seen in X-ray pulsars, most cases show the opposite behavior. Pulse phase-resolved spectral analysis shows a variation in the absorbing column density, N H , over pulse phase. Spectra taken during the pulse profile minima are intrinsically softer compared to the pulse phase-averaged spectrum.

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Timing and spectral studies of the transient X-ray pulsar GX 304−1 during an outburst

Cited by 34 publications

References 32 publications

Suzakuview of the Be/X-ray binary pulsar GX 304-1 during Type I X-ray outbursts

Suzakuview of the Be/X-ray binary pulsar GX 304-1 during Type I X-ray outbursts

Patterns of variability in Be/X-ray pulsars during giant outbursts

Suzakuobservations of the 2013 outburst of KS 1947+300

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