Related papers: Twelve-hour spikes from the Crab Pevatron
Combined with very-long-baseline interferometry measurements, the observations of fast TeV gamma-ray flares probe the structure and emission mechanism of blazar jets. However, only a handful of such flares have been detected to date, and…
We construct a turbulent model of the Crab Nebula's non-thermal emission. The present model resolves a number of long-standing problems of the Kennel-Coroniti (1984) model: (i) the sigma problem; (ii) the hard spectrum of radio electrons;…
We report on the observation of $\gamma$-rays above 25\,GeV from the Crab pulsar (PSR B0532+21) using the MAGIC I telescope. Two data sets from observations during the winter period 2007/2008 and 2008/2009 are used. In order to discuss the…
The BL Lacertae object Markarian 501 was identified as a source of gamma-ray emission at the Whipple Observatory in March 1995. Here we present a flux variability analysis on several times-scales of the 233 hour data set accumulated over…
The Crab pulsar is the only astronomical pulsed source detected above 100 GeV. The emission mechanism of very high energy gamma-ray pulsation is not yet fully understood, although several theoretical models have been proposed. In order to…
We spectrally fit the GeV gamma-ray flares recently-observed in the Crab Nebula by considering a small blob Lorentz-boosted towards us. We point out that the corresponding inverse-Compton flare at TeV--PeV region is more enhanced than…
In 1997 October daily monitoring observations of the Crab pulsar at 327 MHz and 610 MHz with an 85ft telescope in Green Bank, WV showed a jump in the dispersion measure by 0.1 cm$^{-3}$ pc. Pulses were seen simultaneously at both old and…
The Crab Nebula is the only hard X-ray source in the sky that is both bright enough and steady enough to be easily used as a standard candle. As a result, it has been used as a normalization standard by most X-ray/gamma ray telescopes.…
A search for potential point sources of very high energy gamma rays has been carried out on the data taken simultaneously by the HEGRA AIROBICC and Scintillator arrays from August 1994 to March 2000. The list of sought sources includes…
My thesis deals with a fundamental question of high energy gamma-ray astronomy. Namely, I studied the cut-off shape of the Crab pulsar spectrum to distinguish between the leading scenarios for the pulsar models. Pulsars are celestial…
TeV Gamma-ray signals from the Crab Nebula and Mkn 501 were detected with the HEGRA CT1 imaging Cerenkov telescope during periods when the moon was shining and during twilight. This was accomplished by lowering the high voltage supply of…
The blazar 4C 31.03 recently underwent a major gamma-ray outburst at the beginning of 2023 after a prolonged quiescent phase. Fermi-LAT reported a daily average flux of 5x10^-6 phs cm^-2 s^-1, which is about 60 times its average value. We…
We studied the evolution of the X-ray and gamma-ray spectra of the Crab pulsar utilizing the 11-year observations from the Rossi X-ray Timing Explorer (RXTE) and 9-year observations from the Fermi Gamma-ray Space Telescope (FGST). By…
Since 2005, the blazar 3C 454.3 has shown remarkable flaring activity at all frequencies, and during the last four years it has exhibited more than one gamma-ray flare per year, becoming the most active gamma-ray blazar in the sky. We…
We investigate the radiation processes inside supernova remnants which are powered by young pulsars. Using recent model for particle acceleration by the pulsar wind nebulae, we obtain the equilibrium spectra of leptons and nuclei inside the…
X-ray flares are generally supposed to be produced by the later central engine activities, and may share the similar physical origin with prompt emission of gamma-ray bursts (GRBs). In this paper, we have analyzed all significant X-ray…
We present the results of the search for a correlation between giant radio pulses (GRPs) at 1.4 GHz and hard X-rays at 15-75 keV from the Crab pulsar. We made simultaneous ground and satellite observations of the Crab pulsar over 12 hours…
The well studied blazar 3C 279 underwent a giant $\gamma$-ray outburst in 2014 March-April. The measured $\gamma$-ray flux (1.21 $\pm$ 0.10 $\times$ 10$^{-5}$ ph cm$^{-2}$ s$^{-1}$ in 0.1-300 GeV energy range) is the highest detected from…
I. There is growing evidence that pulsars' high energy emission is generated via Inverse Compton mechanism. II. The particles producing Crab flares, and possibly most of the Crab Nebula's high energy emission, are accelerated via…
We report on a detailed analysis of the $\gamma$-ray light curve of NGC 1275 using the Fermi large area telescope data accumulated in 2008-2017. Major $\gamma$-ray flares were observed in October 2015 and December 2016/January 2017 when the…