Related papers: Exploring plasma evolution during Sagittarius A* f…

We report on recent near-infrared (NIR) and X-ray observations of Sagittarius A* (Sgr A*), the electromagnetic manifestation of the ~4x10^6 solar masses super-massive black hole (SMBH) at the Galactic Center. The goal of these coordinated…

There is a large variety in the models explaining blazar flares. Here, we study the flare profile induced by a moving and expanding blob with special emphasize on the gamma-gamma pair production. We first develop a simple semi-analytical…

We perform general relativistic ray-tracing calculations of the transfer of polarized synchrotron radiation through the relativistic accretion flow in Sagittarius (Sgr) A*. Based on a two-temperature magneto-rotational-instability (MRI)…

Studies of the inner few parsecs at the Galactic Centre provide evidence of a supermassive black hole, associated with the unusual, variable radio and infrared source Sgr A*. Our major aim is the study and analysis of the physical processes…

In spite of a large number of global three-dimensional (3D) magneto-hydrodynamical (MHD) simulations of accretion flows and jets being made recently, their astrophysical relevance for realistic situations is not well known. In order to…

The candidate supermassive black hole in the Galactic Centre, Sagittarius A* (Sgr A*), is known to be fed by a radiatively inefficient accretion flow (RIAF), inferred by its low accretion rate. Consequently, radiative cooling has in general…

We present 44 and 226 GHz observations of the Galactic center within 20$"$ of Sgr A*. Millimeter continuum emission at 226 GHz is detected from eight stars that have previously been identified at near-IR and radio wavelengths. We also…

The supermassive black hole, Sagittarius A* (Sgr A*), at the centre of the Milky Way undergoes regular flaring activity which is thought to arise from the innermost region of the accretion flow. We performed the monitoring observations of…

Getman et al. (2021) reports the discovery, energetics, frequencies, and effects on environs of $>1000$ X-ray super-flares with X-ray energies $E_X \sim 10^{34}-10^{38}$~erg from pre-main sequence (PMS) stars identified in the $Chandra$…

Sgr~A* often shows bright, episodic flares observationally, the mechanism of the flares intermittent brightening is not very clear. Many people believe the flares may formed by the non-thermal particles, which can be a consequence of the…

We describe recent results for Sgr A*, M81* and other low luminosity active galactic nuclei. We have conducted linear and circular polarimetry over a frequency range of 1.4 to 230 GHz and detected a variety of phenomena. The polarization…

We have performed monitoring observations of the 3-mm flux density toward the Galactic Center compact radio source Sgr A* with the Australia Telescope Compact Array since 2005 October. Careful calibrations of both elevation-dependent and…

The supermassive black hole Sagittarius A* (Sgr A*) exhibits temporal and spectral variability across the electromagnetic spectrum. However, variability at radio frequencies below ~ 5 GHz for timescales shorter than a day remains largely…

We report the first time-series of broadband infrared (IR) color measurements of Sgr A*, the variable emission source associated with the supermassive black hole at the Galactic Center. Using the laser and natural guide star AO systems on…

Sagittarius A* is a compact radio source at the Galactic center, powered by accretion of fully ionized plasmas into a supermassive black hole. However, the radio emission cannot be produced through the thermal synchrotron process by a…

Despite advances in our understanding of low luminosity active galactic nuclei (LLAGNs), the fundamental details about the mechanisms of radiation and flare/outburst in hot accretion flow are still largely missing. We have systematically…

Flaring activity following gamma-ray bursts (GRBs), observed in both long and short GRBs, signals a long-term activity of the central engine. However, its production mechanism has remained elusive. Here we develop a quantitative model of…

The relatively rapid spatial and temporal variability of the X-ray radiation from some molecular clouds near the Galactic center shows that this emission component is due to the reflection of X-rays generated by a source that was luminous…

The extended X-ray emission observed in the direction of several molecular clouds in the central molecular zone of our Galaxy exhibits spectral and temporal properties consistent with the X-ray echo scenario. This concept postulates that…

Swift-XRT observations of the X-ray emission from gamma ray bursts (GRBs) and during the GRB afterglow have led to many new results during the past two years. One of these exciting results is that approximately 1/3-1/2 of GRBs contain…