Related papers: Recurrent microblazar activity in Cygnus X-1?
The aperiodic X-ray variability in neutron star and black hole X-ray binaries (XRBs), and active galactic nuclei (AGN) shows a characteristic linear relationship between rms amplitude and flux, implying a multiplying-together or `coupling'…
Blazars are a subclass of radio-loud active galactic nuclei (AGNs), where the jet is aligned close to the line of sight. Blazars emission is dominated by non-thermal processes, where Doppler boosted radiation originates from a relativistic…
We propose a gamma-ray burst scenario involving relativistic jets dominated by Poynting flux with alternating toroidal magnetic fields. Such a structure may arise naturally if the jet is formed and powered by the accretion flow in the core…
We present evidence for the presence of a weak compact jet during a soft X-ray state of Cygnus X-1. Very-high-resolution radio observations were taken with the VLBA, EVN and MERLIN during a hard-to-soft spectral state change, showing the…
We present results of monitoring observations of the micro-quasars CygnusX-1 and Cygnus X-3 at 0.61 and 1.28 GHz. The observations were performed with Giant Meter-wave Radio Telescope, GMRT, between 2003 June and 2005 January. Variable,…
Mergers of spinning black holes can give recoil velocities from gravitational radiation up to several thousand km/s. A recoiling supermassive black hole in an AGN retains the inner part of its accretion disk. Marginally bound material…
The origin of the recently discovered new class of transients, X-ray quasi-periodic eruptions (QPEs), remains a puzzle. Due to their periodicity and association with active galactic nuclei (AGN), it is natural to relate these eruptions to…
Thanks to recurrent observations of the black hole binary Cyg X-1 carried out over 15 years the INTEGRAL satellite has collected the largest data set in the hard X-ray band for this source. We have analyzed these data, complemented by data…
We present results from a 20 ksec RXTE observation of the black hole candidate Cyg X-1. We apply self-consistent accretion disk corona models to these hard state data and show that Comptonization in a spherical corona irradiated by soft…
Recent advances in the X-ray and soft gamma-ray observations of accreting black holes and microquasars, in particular, are reviewed. The radiative processes responsible for the emission are discussed briefly. The hybrid thermal/nonthermal…
We have performed a principal component analysis on the X-ray spectra of the microquasar Cygnus X-3 from RXTE, INTEGRAL and Swift during a major flare ejection event in 2006 May-July. The analysis showed that there are two main variability…
In some Seyfert Galaxies, the hard X-rays that produce fluorescent emission lines are thought to be generated in a hot corona that is compact and located at only a few gravitational radii above the supermassive black hole. We consider the…
Investigating the spectral and temporal characteristics of the X-rays coming from Sagittarius A* (Sgr A*) is essential to our development of a more complete understanding of the emission mechanisms in this supermassive black hole located at…
The study of fast variability properties in X-ray binaries advances our understanding of the physical processes and geometric properties of the accretion flow around the compact object. In this work, we study the evolution of the timing…
We present millimetre wavelength observations of the black hole candidate X-ray binary Cygnus X-1 which indicate a suppression, or quenching, of the emission as the source switches to a softer X-ray state. Combining the data with those for…
We analyse the aperiodic flaring features, also known as shots, observed in Cyg X-1 in the 0.1-80 keV energy band using a 6.39 ks simultaneous observation with AstroSat and NICER. We detect 49 simultaneous shots in the soft and hard X-ray…
We report on the 0.5--200 keV spectral properties of Cyg X-1 observed at different epochs with the Narrow Field Instruments of the BeppoSAX satellite. The source was in its soft state during the first observation of 1996 June. In the second…
We have analyzed a Chandra HETGS spectrum of the Galactic black hole Cygnus X-1, obtained at a source flux which is approximately twice that commonly observed in its persistent low-intensity, spectrally-hard state. We find a myriad of…
We use time domain analysis techniques to investigate the rapid variability of Cygnus X-1. We show that the cross-correlation functions between hard and soft energy bands reach values very close to unity and peak at a lag of less than 2…
Short-term variability of X-ray continuum spectra has been reported for several Active Galactic Nuclei. Significant X-ray flux variations are observed within time scales down to 10^3-10^5 seconds. We discuss short variability time scales in…