X‐Ray Pulses from Accretion Columns: Contributions to the Energy Dependence of the Pulse Shape

Kraus, Ute; Zahn, Corvin; Weth, Christian von der; Ruder, H.

doi:10.1086/375011

Cited by 27 publications

(37 citation statements)

References 23 publications

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“…Indeed, depending on to the geometry of the emitting region and the observer's line of sight, this effect could make the accretion columns visible from all directions (Kraus 2001;Kraus et al 2003), thus affecting the pulse profile in a significant way. In addition, the pulse profiles luminosity dependence probably reflects a change in the physical condition of the accretion column.…”

Section: Timing Resultsmentioning

confidence: 99%

Luminosity-dependent spectral and timing properties of the accreting pulsar GX 304−1 measured with INTEGRAL

Malacaria

Klochkov

Santangelo

et al. 2015

A&A

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Context. Be/X-ray binaries show outbursts with peak luminosities up to a few times 10 37 erg/s, during which they can be observed and studied in detail. Most (if not all) Be/X-ray binaries harbor accreting pulsars, whose X-ray spectra in many cases contain cyclotron resonant scattering features related to the magnetic field of the sources. Spectral variations as a function of luminosity and of the rotational phase of the neutron star are observed in many accreting pulsars. Aims. We explore X-ray spectral and timing properties of the Be/X-ray binary GX 304-1 during an outburst episode. Specifically, we investigate the behavior of the cyclotron resonant scattering feature, the continuum spectral parameters, the pulse period, and the energy-and luminosity-resolved pulse profiles. Methods. We analyze the INTEGRAL data from the two JEM-X modules, ISGRI and SPI, covering the 2012 January−February outburst, divided into six observations. We obtain pulse profiles in two energy bands, phase-averaged and phase-resolved spectra for each observation. We combine the luminosity-resolved spectral and timing analysis to probe the accretion geometry and the beaming patterns of the rotating neutron star. Results. We confirm the positive luminosity dependence of the cyclotron line energy in GX 304-1 and report a dependence of the photon index on luminosity. Using a pulse-phase connection technique, we find a pulse period solution valid for the entire outburst. Our pulse-phase resolved analysis shows that the centroid energy of the cyclotron line varies only slightly with pulse phase, while other spectral parameters show more pronounced variations. Our results are consistent with a scenario in which, as the pulsar rotates, we are exploring only a small portion of its beam pattern.

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Section: Timing Resultsmentioning

confidence: 99%

Luminosity-dependent spectral and timing properties of the accreting pulsar GX 304−1 measured with INTEGRAL

Malacaria

Klochkov

Santangelo

et al. 2015

A&A

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show abstract

“…This was discussed by Kraus et al (2003), who find that scattering in the upper accretion flow might affect the formation of the pulse-profile and spectra in a major way and, in fact, be responsible for the majority of the hard photons coming from the source. The magnetic field in scattering region might already be compatible with the one estimated from the observed CRSF energy.…”

Section: Discussionmentioning

confidence: 99%

Supergiant, fast, but not so transient 4U 1907+09

Doroshenko

Santangelo

Ducci

et al. 2012

A&A

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We have investigated the dipping activity observed in the high-mass X-ray binary 4U 1907+09 and shown that the source continues to pulsate in the "off" state, noting that the transition between the "on" and "off" states may be either dip-like or flare-like. This behavior may be explained in the framework of the "gated accretion" scenario proposed to explain the flares in supergiant fast X-ray transients (SFXTs). We conclude that 4U 1907+09 might prove to be a missing link between the SFXTs and ordinary accreting pulsars.

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“…Interpreting pulse profiles in terms of the underlying emission pattern is far from evident since various effects, including highly anisotropic cross-sections for emission and scattering and lightbending around the neutron star must be taken into account (Kraus et al 2003). For A 0535+26, Caballero et al (2011a) have disentangled the contribution of the two single pole components for A 0535+26 using pulse profiles from the 2005 August normal outburst.…”

Section: Pulse Profile Studymentioning

confidence: 99%

X-Ray and Optical Observations of a 0535+26

Camero-Arranz

Finger

Wilson-Hodge

et al. 2012

ApJ

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We present recent contemporaneous X-ray and optical observations of the Be/X-ray binary system A 0535+26 with the Fermi/Gamma-ray Burst Monitor (GBM) and several ground-based observatories. These new observations are put into the context of the rich historical data (since ∼1978) and discussed in terms of the neutron-star-Be-disk interaction. The Be circumstellar disk was exceptionally large just before the 2009 December giant outburst, which may explain the origin of the unusual recent X-ray activity of this source. We found a peculiar evolution of the pulse profile during this giant outburst, with the two main components evolving in opposite ways with energy. A hard 30-70 mHz X-ray quasi-periodic oscillation was detected with GBM during this 2009 December giant outburst. It becomes stronger with increasing energy and disappears at energies below 25 keV. In the long term a strong optical/X-ray correlation was found for this system, however in the medium term the Hα equivalent width and the V-band brightness showed an anti-correlation after ∼2002 August. Each giant X-ray outburst occurred during a decline phase of the optical brightness, while the Hα showed a strong emission. In late 2010 and before the 2011 February outburst, rapid V /R variations are observed in the strength of the two peaks of the Hα line. These had a period of ∼25 days and we suggest the presence of a global one-armed oscillation to explain this scenario. A general pattern might be inferred, where the disk becomes weaker and shows V /R variability beginning ∼6 months following a giant outburst.

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X‐Ray Pulses from Accretion Columns: Contributions to the Energy Dependence of the Pulse Shape

Cited by 27 publications

References 23 publications

Luminosity-dependent spectral and timing properties of the accreting pulsar GX 304−1 measured with INTEGRAL

Luminosity-dependent spectral and timing properties of the accreting pulsar GX 304−1 measured with INTEGRAL

Supergiant, fast, but not so transient 4U 1907+09

X-Ray and Optical Observations of a 0535+26

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