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Aineistot 1-10 / 31
POLARIZATION MODULATION FROM LENSE-THIRRING PRECESSION IN X-RAY BINARIES
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It has long been recognized that quasi-periodic oscillations (QPOs) in the X-ray light curves of accreting black hole. and neutron star binaries have the potential to be powerful diagnostics of strong field gravity. ...
The 2015 outburst of the accretion-powered pulsar IGR J00291+5934: INTEGRAL and Swift observations
The pulsar IGR J00291 + 5934 is the fastest-known accretion-powered X-ray pulsar, discovered during a transient outburst in 2004. In this paper, we report on INTEGRAL and Swift observations during the 2015 outburst, which ...
The unusual behavior of the young X-ray pulsar SXP 1062 during the 2019 outburst
We present the results of the first dedicated observation of the young X-ray pulsar SXP 1062 in the broad X-ray energy band obtained during its 2019 outburst with the NuSTAR and XMM-Newton observatories. The analysis of ...
X-ray burst-induced spectral variability in 4U 1728-34
Aims. INTEGRAL has been monitoring the Galactic center region for more than a decade. Over this time it has detected hundreds of type-I X-ray bursts from the neutron star low-mass X-ray binary 4U 1728-34, also known as the ...
Broadband X-ray spectra and timing of the accreting millisecond pulsar Swift J1756.9-2508 during its 2018 and 2019 outbursts
<p>The accreting millisecond X-ray pulsar Swift J1756.9-2508 launched into an outburst in April 2018 and June 2019 - 8.7 years after the previous period of activity. We investigated the temporal, timing, and spectral properties of these two outbursts using data from NICER, XMM-Newton, NuSTAR, INTEGRAL, Swift, and Insight-HXMT. The two outbursts exhibited similar broadband spectra and X-ray pulse profiles. For the first time, we report the detection of the pulsed emission up to ∼100 keV that was observed by Insight-HXMT during the 2018 outburst. We also found the pulsation up to ∼60 keV that was observed by NICER and NuSTAR during the 2019 outburst. We performed a coherent timing analysis combining the data from the two outbursts. The binary system is well described by a constant orbital period over a time span of ∼12 years. The time-averaged broadband spectra are well fitted by the absorbed thermal Comptonization model COMPPS in a slab geometry with an electron temperature, kT<sub>e</sub>=40-50 keV, Thomson optical depth τ ∼ 1.3, blackbody seed photon temperature kT<sub>bb, seed </sub>∼0.7-0.8 keV, and hydrogen column density of N<sub>H</sub> ∼ 4.2x10<sup>22</sup> cm<sup>-2</sup>. We searched the available data for type-I (thermonuclear) X-ray bursts, but found none, which is unsurprising given the estimated low peak accretion rate (≈0.05 of the Eddington rate) and generally low expected burst rates for hydrogen-poor fuel. Based on the history of four outbursts to date, we estimate the long-term average accretion rate at roughly 5x10<sup>-12</sup> M<sub>⊙</sub> yr<sup>-1</sup> for an assumed distance of 8 kpc. The expected mass transfer rate driven by gravitational radiation in the binary implies the source may be no closer than 4 kpc. Swift J1756.9-2508 is the third low mass X-ray binary exhibiting "double" outbursts, which are separated by much shorter intervals than what we typically see and are likely to result from interruption of the accretion flow from the disk onto the neutron star. Such behavior may have important implications for the disk instability model.</p>...
Evidence for the Photoionization Absorption Edge in a Photospheric Radius Expansion X-Ray Burst from GRS 1747-312 in Terzan 6
Thermonuclear X-ray bursts on the surface of neutron stars (NSs) can enrich the photosphere with metals, which may imprint photoionization edges on the burst spectra. We report here the discovery of absorption edges in the ...
Spectral and temporal properties of Compton scattering by mildly relativistic thermal electrons
We have obtained new solutions and methods for the process of thermal. Comptonization, We modify the solution to the kinetic equation of Sunyaev and Titarchuk to allow its application up to mildly relativistic electron ...
Cyclotron emission, absorption, and the two faces of X-ray pulsar A 0535+262
Deep NuSTAR observation of X-ray pulsar A 0535+262, performed at a very low luminosity of similar to 7 x 10(34) erg s(-1), revealed the presence of two spectral components. We argue that the high-energy component is ...
Investigating the peculiar emission from the new VHE gamma-ray source H1722+119
The Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes observed the BL Lac object H1722+119 (redshift unknown) for six consecutive nights between 2013 May 17 and 22, for a total of 12.5 h. The observations ...
Evidence for the radiation-pressure dominated accretion disk in bursting pulsar GRO J1744-28 using timing analysis
The X-ray pulsar GRO J1744-28 is a unique source that shows both pulsations and type-II X-ray bursts, allowing studies of the interaction of the accretion disk with the magnetosphere at huge mass-accretion rates exceeding ...