Related papers: Probing the gamma-ray variability in 3C279 using b…
We report on long-term multi-wavelength monitoring of blazar Mrk~421 from 2010 to 2011. The source exhibited extreme X-ray flares in 2010. Our research group performed optical photopolarimetric follow-up observations using the Kanata…
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…
We report the first detection of GeV gamma-ray flaring activity from the compact symmetric object (CSO)-like source 4C 76.03, based on 17 years of Fermi-LAT observations. Its long-term, time-averaged gamma-ray properties are consistent with…
We monitored 3C273 with VLBI at 15-86 GHz since 1990. We discuss component trajectories, opacity effects at the jet base, a rotating and perhaps precessing jet, and outburst-ejection relations from Gamma-ray to radio bands.
We have been using the 0.76-m Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory to optically monitor a sample of 157 blazars that are bright in gamma rays, being detected with high significance ($\ge 10\sigma$) in one year by…
We present the results of our follow-up observation program of gamma-ray sources detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. 26 blazars and 39 sources unidentified at other wavelengths were…
We are leading a comprehensive multi-waveband monitoring program of 34 gamma-ray bright blazars designed to locate the emission regions of blazars from radio to gamma-ray frequencies. The "maps" are anchored by sequences of images in both…
Since mid-2007 we have carried out a dedicated long-term monitoring programme at 15 GHz using the Owens Valley Radio Observatory 40 meter telescope. One of the main goals of this programme is to study the relation between the radio and…
The binary system PSR B1259-63/LS 2883 is well sampled in radio, X-rays, and TeV gamma-rays, and shows orbital phase-dependent variability in these frequencies. The first detection of GeV gamma-rays from the system was made around the 2010…
We have studied long-term optical, ultraviolet (UV) and X-ray observations of OJ 287 collected with the UVOT and XRT instruments mounted on board the Swift satellite to quantify spectral and temporal variability patterns observed during…
We report first results of a multifrequency campaign from radio to hard X-ray energies of the prominent gamma-ray blazar 3C 279, which was organised around an INTEGRAL ToO observation in January 2006, and triggered on its optical state. The…
We present a comprehensive 5-43 GHz VLBA study of the blazar 3C 273 initiated after an onset of a strong $\gamma$-ray flare in this source. We have analyzed the kinematics of new-born components, light curves, and position of the apparent…
The Compton Gamma-Ray Observatory (CGRO) experiments EGRET and COMPTEL observed the Virgo sky region continuously for 7 weeks between December 10, 1996 and January 28, 1997. The prominent quasar 3C~273 was found to be the brightest source…
The COMPTEL experiment aboard the Compton Gamma-Ray Observatory (CGRO) has observed the gamma-ray blazar 3C 279 several times between April 1991 and September 1995. This paper reports on a consistent analysis of these observations using the…
The TeV blazar Ton 599 has exhibited a peculiar flare in 2017 November. The temporal variation of the source is studied using simultaneous $\gamma$-ray data from $\textit{Fermi}$ Large Area Telescope and radio data from Owens Valley Radio…
A large radio outburst from Sgr A* was observed during the VLA weekly monitoring program at 2 cm, 1.3 cm and 7 mm, nearly coincident with the brightest X-ray flare detected to date with the XMM-Newton X-ray Observatory on 2002-10-03. The…
An $R$--band photopolarimetric variability analysis of the TeV bright blazar W Comae, between 2008 February 28 and 2013 May 17, is presented. The source showed a gradual tendency to decrease its mean flux level with a total change of…
To fully exploit the scientific potential of the Fermi mission, we initiated the F-GAMMA program. Between 2007 and 2015 it was the prime provider of complementary multi-frequency monitoring in the radio regime. We quantify the radio…
We perform a blind search for the variability of the gamma-ray sky in the energy range E>1 GeV using 308 weeks of the Fermi-LAT data. We use the technique based on the comparison of the weekly photon counts and exposures in sky pixels by…
On 2019 October 25, the Fermi-Large Area Telescope observed the first gamma-ray flare from the radio-loud narrow-line Seyfert 1 (NLSy 1) galaxy PKS 2004$-$447 ($z=0.24$). We report on follow-up observations in the radio, optical-UV, and…