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X-ray emitting gaseous coronae around massive galaxies are a basic prediction of galaxy formation models. Although the coronae around spiral galaxies offer a fundamental test of these models, observational constraints on their…
IGR J17091-3624 is the only black hole X-ray binary candidate, aside from the well-studied black hole system GRS 1915+105, observed to exhibit a wide range of structured variability patterns in its light curves. In 2025, the source…
Solar radio bursts exhibit complex fine structures that reveal intricate coronal plasma dynamics. Here, we report detection of spike-like repeating burst pairs, characterized by two short-lived (0.1-2 s), narrowband components separated by…
Coronal loop observations have existed for many decades yet the precise shape of these fundamental coronal structures is still widely debated since the discovery that they appear to undergo negligible expansion between their footpoints and…
Active galactic nuclei (AGN) are complex phenomena. At the heart of an AGN is a relativistic accretion disk around a spinning supermassive black hole (SMBH) with an X-ray emitting corona and, sometimes, a relativistic jet. On larger scales,…
Recently a distinctive class of hard X ray (HXR) sources located in the corona was found, which implies that the collisionally thick target model (CTTM) applies even to the corona. We investigated whether this idea can independently be…
The hard X-ray emission observed in accreting compact sources is believed to be produced by inverse Compton scattering of soft photons arising from the accretion disc by energetic electrons thermally distributed above the disc, the…
We present a detailed study of the observable effects of photoionization and Comptonization of line and continuum radiation from a cold accretion disk with a thin, warm, photoionized transition layer in the framework of self-consistent…
The search for diffuse non-thermal inverse Compton (IC) emission from galaxy clusters at hard X-ray energies has been undertaken with many instruments, with most detections being either of low significance or controversial. Background and…
We test accurate models of Comptonization spectra over the high quality data of the BeppoSAX long look at NGC 5548. The data are well represented by a plane parallel corona with an inclination angle of 30$^{\circ}$, a soft photon…
In magnetic cataclysmic variables (CVs), X-ray emission regions are located close to the white dwarf surface, which is expected to reflect a significant fraction of intrinsic X-rays above 10 keV, producing a Compton reflection hump.…
The bright Seyfert 1 galaxy MCG-6-30-15 has provided some of the best evidence to date for the existence of supermassive black holes in active galactic nuclei. Observations with ASCA revealed an X-ray iron line profile shaped by strong…
The Chandra X-ray observatory monitored the single cool star, AB Doradus, continuously for a period lasting 88ksec (1.98 Prot) in 2002 December with the LETG/HRC-S. The X-ray lightcurve shows significant rotational modulation. It can be…
Galactic black hole coronae are composed of a hot, magnetized plasma. The spectral energy distribution produced in this component of X-ray binaries can be strongly affected by different interactions between locally injected relativistic…
We report on the \nustar{} observation of the atoll type neutron star (NS) low-mass X-ray binary GX~3+1 performed on 17 October 2017. The source was found in a soft X-ray spectral state with $3-70$keV luminosity of $L_\text{X}\sim3\times…
A NuSTAR/Swift observation of the luminous Seyfert 1 galaxy 1H 0419-577 taken during 2015 reveals one of the most extreme high energy cut-offs observed to date from an AGN - an origin due to thermal Comptonization would imply a remarkably…
We present analysis and results from the Reflection Grating Spectrometer during the 320 ks XMM observation of the Seyfert 1 galaxy MCG-6-30-15. The spectrum is marked by a sharp drop in flux at 0.7 keV which has been interpreted by…
Most of the Active Galactic Nuclei (AGN) are radio-quiet (RQ) and, differently from radio-loud (RL) AGN, do not show signature of large-scale and powerful jets. The physical origin of their radio emission remains then broadly unclear. The…
In this paper, we make a multi-epoch analysis of NGC 1052, one of the prototypical LLAGN, using XMM-Newton, Suzaku and NuSTAR observations, taken from 2001 to 2017. This is the first time that results from NuSTAR observations are reported…
We identify sources with extremely hard X-ray spectra (i.e., with photon indices of Gamma<0.6 in the 13 sq. deg. NuSTAR serendipitous survey, to search for the most highly obscured AGNs detected at >10 keV. Eight extreme NuSTAR sources are…