The production of artificial light curves with known statistical and variability properties is of
great importance in astrophysics. Consolidating the confidence levels during cross …

Aims. Variability at all observed wavelengths is a distinctive property of active galactic nuclei
(AGN). Hard X-rays provide us with a view of the innermost regions of AGN, mostly unbiased …

Various attempts have been made in the literature at describing the origin and the physical
mechanisms behind flaring events in blazars with radiative emission models, but detailed …

Hard X-ray spectra of 28 bright Seyfert galaxies observed with INTEGRAL were analysed
together with the X-ray spectra from XMM–Newton, Suzaku and RXTE. These broad-band …

We explore the relationship between active galactic nuclei (AGN) and star formation in a
sample of 513 optically luminous type 1 quasars up to redshifts of∼ 4 hosting extremely …

Context. The HAGAR Telescope Array at Hanle, Ladakh has been regularly monitoring the
nearby blazar Mkn 421 for the past seven years. Aims. Blazars show flux variability in all …

Aims. The nearby TeV blazar 1ES 1959+ 650 (z= 0.047) was reported to be in flaring state
during June–July 2016 by Fermi-LAT, FACT, MAGIC and VERITAS collaborations. We …

Aims. The nearby (z= 0.031) TeV blazar Mrk 421 was reported to be in a high state of flux
activity since November, 2009. We aim to investigate possible changes in the physical …

Context. Variability, both in X-ray and optical/UV, affects the well-known anti-correlation
between the α ox spectral index and the UV luminosity of active galactic nuclei, contributing …

Abstract We report a 325 (− 7,+ 8) day quasi-periodic oscillation (QPO) in the X-ray emission
of the blazar Mkn 421 based on data obtained with the Rossi X-ray Timing Explorer satellite …