Search

We report the quasi-simultaneous INTEGRAL, SWIFT, and NuSTAR observations showing spectral state transitions in the neutron star low-mass X-ray binary 1RXS J180408.9−342058 during its 2015 outburst. We present results of the analysis of high-quality broad energy band (0.8–200 keV) data in three different spectral states: high/soft, low/very-hard, and transitional state. The broadband spectra can be described in general as the sum of thermal Comptonization and reflection due to illumination of an optically thick accretion disk. During the high/soft state, blackbody emission is generated from the accretion disk and the surface of the neutron star. This emission, measured at a temperature of kTbb ∼ 1.2 keV, is then Comptonized by a thick corona with an electron temperature of ∼2.5 keV. For the transitional and low/very-hard state, the spectra are successfully explained with emission from a double Comptonizing corona. The first component is described by thermal Comptonization of seed disk/neutron star photons (kTbb ∼ 1.2 keV) by a cold corona cloud with kTe ∼ 8–10 keV, while the second one originates from lower temperature blackbody photons (kTbb ≤ 0.1 keV) Comptonized by a hot corona (kTe ∼ 35 keV). Finally, from NuSTAR observations, there is evidence that the source is a new clocked burster. The average time between two successive X-ray bursts corresponds to ∼7.9 and ∼4.0 ks when the persistent emission decreases by a factor of ∼2, moving from a very hard to transitional state. The accretion rate () and the decay time of the X-ray bursts longer than ∼30 s suggest that the thermonuclear emission is due to mixed H/He burning triggered by thermally unstable He ignition. [ABSTRACT FROM AUTHOR]

Giant radio galaxies (GRG) are the largest single entities in the universe, having a projected linear size exceeding 0.7 Mpc, which implies that they are also quite old objects. They are not common, representing a fraction of only ∼6% in samples of bright radio galaxies. While a census of about 300 of these objects has been built in the past years, still no light has been shed on the conditions necessary to allow such an exceptional growth, whether of environmental nature or linked to the inner accretion properties. Recent studies found that samples of radio galaxies selected from hard X-ray active galactic nuclei catalogs selected from the International Gamma-Ray Astrophysics Laboratory (INTEGRAL)/the Imager on Board the INTEGRAL Satellite and Swift/the Burst Alert Telescope (thus at energies >20 keV) present a fraction of GRG four times larger than what is found in radio-selected samples. We present radio observations of 15 nuclei of hard-X-ray-selected GRG, finding for the first time a large fraction (61%) of young radio sources at the center of Mpc-scale structures. Being at the center of GRG, these young nuclei may be undergoing a restarting activity episode, suggesting a link between the detected hard X-ray emission—due to the ongoing accretion—and the reactivation of the jets. [ABSTRACT FROM AUTHOR]

The accretion mechanism producing the short flares observed from the Supergiant Fast X-ray Transients (SFXT) is still highly debated and forms a major part in our attempts to place these X-ray binaries in the wider context of the High Mass X-ray Binaries. We report on a 216 ks INTEGRAL observation of the SFXT IGR J16328-4726 (2014 August 24–27) simultaneous with two fixed-time observations with XMM-Newton (33 and 20 ks) performed around the putative periastron passage, in order to investigate the accretion regime and the wind properties during this orbital phase. During these observations, the source has shown luminosity variations, from to , linked to spectral properties changes. The soft X-ray continuum is well modeled by a power law with a photon index varying from ∼1.2 up to ∼1.7 and with high values of the column density in the range of . We report on the presence of iron lines at ∼6.8–7.1 keV, suggesting that the X-ray flux is produced by the accretion of matter from the companion wind characterized by density and temperature inhomogeneities. [ABSTRACT FROM AUTHOR]