The large-scale morphology of the radio jets in microquasar GRS 1758-258 has been changing in the last decades. Available radio maps show hints of apparent precession. Here, we fit data with a simple kinematical model and perform an analysis of the possible origins and implications of precession in this system. From our study, that includes an additional observing epoch, we are able to confirm...
The supersonic motion of a pulsar in the ambient medium usually renders pulsar wind nebulae with morphologically bow-shaped shocks and/or cometary tails. Chandra, with its unprecedented angular resolution and high sensitivity has proved a great success in the detection and precise characterisation of these fast-moving pulsars. In particular, with an increasing number of detected supersonic...
Particle acceleration at stationary and moving internal shocks is one of the principal mechanisms to explain the variable synchrotron emission, seen from the radio to the X-ray band, from relativistic jets in radio-loud active galactic nuclei. To reproduce the light curves associated with these shocks, we perform SRMHD simulations of magnetised relativistic
transverse-structured jets using...
We study the requirement on the jet power in the conventional p-gamma models (photo pion production and Bethe-Heitler pair production) for TeV BL Lac objects. We select a sample of TeV BL Lac objects whose SEDs are difficult to be explained by the one-zone leptonic model. Based on the relation between the p - gamma interaction efficiency and the opacity of absorption, we find that detection of...
About forty (Mrk 421, Mrk 501, 1ES 1959+650, PG 1553+113 and others) northern TeV extragalactic sources have been discovered during last twenty five years. Most of them (2/3) we are monitoring in Abastumani Observatory during 20 years using 125-cm and dedicated 70-cm meniscus telescopes. All observations (over 3500 nights) have been conducted with Apogee Ap6E and SBIG ST-6 CCD cameras in BVRI...
We present results of spectrometric studies based on the observations of very strong AGN flares in high and very-high-energy bands and discuss their implications regarding the origin of radiation mechanisms.
Gamma-ray binaries, which contain a massive star and a compact object, are very interesting astrophysical laboratories because particle acceleration and radiation/absorption mechanisms are modulated by the orbital phase. However, only 7 of such sources are currently known: 2 composed of an O-type star and 5 of a Be-type star, being the systems with an O-type star runaways with respect to their...
To study optical variability of extragalactic sources during last twenty years we are conducting in Abastumani Observatory a long-term monitoring campaign using dedicated telescopes, which allowed collecting 320000 CCD frames during ~3500 nights. This extensive monitoring campaign a few dozen blazars first five years was carried out in BVRI bands and later on from 2002 mainly in R band using...
The acceleration site for UHECR is still an open question despite extended research and GRBs are considered one of the most promising source candidates. Under the likely assumption that electrons are also accelerated at the UHECR acceleration site, synchrotron emission from these co-accelerated electrons is inevitable. We characterize this synchrotron emission and compare it to observed GRB...
