Search Publications
Properties of AGN coronae in the NuSTAR era
Fabian, A. C.; Reynolds, C. S.; Lohfink, A. +3 more
The focusing optics of NuSTAR have enabled high signal-to-noise ratio spectra to be obtained from many X-ray bright active galactic nuclei (AGN) and galactic black hole binaries (BHB). Spectral modelling then allows robust characterization of the spectral index and upper energy cutoff of the coronal power-law continuum, after accounting for reflec…
Photohadronic origin of γ -ray BL Lac emission: implications for IceCube neutrinos
Padovani, P.; Resconi, E.; Mastichiadis, A. +2 more
The recent IceCube discovery of 0.1-1 PeV neutrinos of astrophysical origin opens up a new era for high-energy astrophysics. Although there are various astrophysical candidate sources, a firm association of the detected neutrinos with one (or more) of them is still lacking. A recent analysis of plausible astrophysical counterparts within the error…
The soft γ-ray pulsar population: a high-energy overview
Kuiper, L.; Hermsen, W.
At high-energy γ-rays (>100 MeV), the Large Area Telescope (LAT) on the Fermi satellite already detected more than 145 rotation-powered pulsars (RPPs), while the number of pulsars seen at soft γ-rays (20 keV-30 MeV) remained small. We present a catalogue of 18 non-recycled RPPs from which presently non-thermal pulsed emission has been securely …
Multi-wavelength observations of the binary system PSR B1259-63/LS 2883 around the 2014 periastron passage
Krivonos, R.; Tsygankov, S.; Tomsick, J. A. +16 more
We report on the results of the extensive multi-wavelength campaign from optical to GeV γ-rays of the 2014 periastron passage of PSR B1259-63, which is a unique high-mass γ-ray emitting binary system with a young pulsar companion. Observations demonstrate the stable nature of the post-periastron GeV flare and prove the coincidence of the flare wit…
Identification of a new γ-ray-emitting narrow-line Seyfert 1 galaxy, at redshift ∼1
Komossa, S.; Yuan, Weimin; Zhou, Hongyan +4 more
We report on the identification of a new γ-ray-emitting narrow-line Seyfert 1 (NLS1) galaxy, SDSS J122222.55+041315.7, which increases the number of known objects of this remarkable but rare type of active galactic nuclei to seven. Its optical spectrum, obtained in the Sloan Digital Sky Survey-Baryon Oscillation Spectroscopic Survey, reveals a bro…
Positive correlation between the cyclotron line energy and luminosity in sub-critical X-ray pulsars: Doppler effect in the accretion channel
Tsygankov, Sergey S.; Mushtukov, Alexander A.; Suleimanov, Valery F. +2 more
Cyclotron resonance scattering features observed in the spectra of some X-ray pulsars show significant changes of the line centroid energy with the pulsar luminosity. Whereas for bright sources above the so-called critical luminosity, these variations are established to be connected with the appearance of the high-accretion column above the neutro…
The 1.4-GHz radio properties of hard X-ray-selected AGN
Bird, A. J.; Ubertini, P.; Malizia, A. +7 more
We have analysed the NRAO Very Large Array Sky Survey and Sydney University Molonglo Sky Survey data at 1.4 GHz and 843 MHz for a well-defined complete sample of hard X-ray AGN observed by INTEGRAL. A large number (70/79) of sources are detected in the radio band, showing a wide range of radio morphologies, from unresolved or slightly resolved cor…
Does the obscured AGN fraction really depend on luminosity?
Krivonos, R.; Sazonov, S.; Churazov, E.
We use a sample of 151 local non-blazar active galactic nuclei (AGN) selected from the INTEGRAL all-sky hard X-ray survey to investigate if the observed declining trend of the fraction of obscured (i.e. showing X-ray absorption) AGN with increasing luminosity is mostly an intrinsic or selection effect. Using a torus-obscuration model, we demonstra…
A magnetic reconnection model for explaining the multiwavelength emission of the microquasars Cyg X-1 and Cyg X-3
del Valle, M. V.; de Gouveia Dal Pino, E. M.; Khiali, B.
Recent studies have indicated that cosmic ray acceleration by a first-order Fermi process in magnetic reconnection current sheets can be efficient enough in the surrounds of compact sources. In this work, we discuss this acceleration mechanism operating in the core region of galactic black hole binaries (or microquasars) and show the conditions un…
SXP 5.05 = IGR J00569-7226: using X-rays to explore the structure of a Be star's circumstellar disc
Haberl, F.; Udalski, A.; Bartlett, E. S. +5 more
On MJD 56590-1 (2013 Oct 25-26), observations of the Magellanic Clouds by the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) observatory discovered a previously unreported bright, flaring X-ray source. This source was initially given the identification IGR J00569-7226. Subsequent multiwavelength observations identified the system as ne…