Search Publications
The neutron star transient and millisecond pulsar in M28: from sub-luminous accretion to rotation-powered quiescence
Heinke, Craig; Bahramian, Arash; Homan, Jeroen +6 more
The X-ray transient IGR J18245-2452 in the globular cluster M28 contains the first neutron star (NS) seen to switch between rotation-powered and accretion-powered pulsations. We analyse its 2013 March-April 25 d long outburst as observed by Swift, which had a peak bolometric luminosity of ∼6 per cent of the Eddington limit (LEdd), and g…
GRB 130925A: an ultralong gamma ray burst with a dust-echo afterglow, and implications for the origin of the ultralong GRBs
Lien, A.; Sánchez-Ramírez, R.; Götz, D. +24 more
GRB 130925A was an unusual gamma ray burst (GRB), consisting of three distinct episodes of high-energy emission spanning ∼20 ks, making it a member of the proposed category of `ultralong' bursts. It was also unusual in that its late-time X-ray emission observed by Swift was very soft, and showed a strong hard-to-soft spectral evolution with time. …
GRB 140206A: the most distant polarized gamma-ray burst
Covino, S.; D'Avanzo, P.; Melandri, A. +4 more
The nature of the prompt gamma-ray emission of gamma-ray bursts (GRBs) is still far from being completely elucidated. The measure of linear polarization is a powerful tool that can be used to put further constraints on the content and magnetization of the GRB relativistic outflows, as well as on the radiation processes at work. To date, only a han…
Jet contributions to the broad-band spectrum of Cyg X-1 in the hard state
Stawarz, Łukasz; Zdziarski, Andrzej A.; Sikora, Marek +1 more
We apply the jet model developed in the preceding paper of Zdziarski et al. to the hard-state emission spectra of Cyg X-1. We augment the model for the analytical treatment of the particle evolution beyond the energy dissipation region, and allow for various forms of the acceleration rate. We calculate the resulting electron and emission spectra a…
Bright flares in supergiant fast X-ray transients
Sidoli, L.; Postnov, K.; Paizis, A. +1 more
At steady low-luminosity states, supergiant fast X-ray transients (SFXTs) can be at the stage of quasi-spherical settling accretion on to slowly rotating magnetized neutron stars from the OB-companion winds. At this stage, a hot quasi-static shell is formed above the magnetosphere, the plasma entry rate into magnetosphere is controlled by (ineffic…
A propeller scenario for the gamma-ray emission of low-mass X-ray binaries: the case of XSS J12270-4859
Torres, D. F.; Li, Jian; Papitto, A.
XSS J12270-4859 is the only low-mass X-ray binary (LMXB) with a proposed persistent gamma-ray counterpart in the Fermi-Large Area Telescope domain, 2FGL 1227.7-4853. Here, we present the results of the analysis of recent INTEGRAL observations, aimed at assessing the long-term variability of the hard X-ray emission, and thus the stability of the ac…
Cumulative luminosity distributions of supergiant fast X-ray transients in hard X-rays
Sidoli, L.; Paizis, A.
We have analysed in a systematic way about nine years of INTEGRAL data (17-100 keV) focusing on supergiant fast X-ray transients (SFXTs) and three classical high-mass X-ray binaries (HMXBs). Our approach has been twofold: image-based analysis, sampled over a ∼ks time frame to investigate the long-term properties of the sources and light-curve-base…
The multiwavelength polarization of Cygnus X-1
Shahbaz, Tariq; Russell, David M.
Polarization measurements of the microquasar Cygnus X-1 exist at γ-ray, X-ray, ultraviolet, optical and radio frequencies. The γ-ray emission has been shown to be highly linearly polarized. Here, we present new infrared polarimetric data of Cygnus X-1 taken with the 10.4 m Gran Telescopio Canarias and the 4.2 m William Herschel Telescope. We show …
New insights on accretion in supergiant fast X-ray transients from XMM-Newton and INTEGRAL observations of IGR J17544-2619
Hill, A. B.; Sidoli, L.; Bird, A. J. +4 more
XMM-Newton observations of the supergiant fast X-ray transient IGR J17544-2619 are reported and placed in the context of an analysis of archival INTEGRAL/IBIS data that provide a refined estimate of the orbital period at 4.9272 ± 0.0004 d. A complete outburst history across the INTEGRAL mission is reported. Although the new XMM-Newton observations…
The average 0.5-200 keV spectrum of local active galactic nuclei and a new determination of the 2-10 keV luminosity function at z ≈ 0
Ballantyne, D. R.
The broad-band X-ray spectra of active galactic nuclei (AGNs) contains information about the nuclear environment from Schwarzschild radii scales (where the primary power law is generated in a corona) to distances of ∼1 pc (where the distant reflector may be located). In addition, the average shape of the X-ray spectrum is an important input into X…