Related papers: Optical Variability of the Radio Source J 1128+592…

The optical (BVRI) and radio (8.4 GHz) light curves of S5 1803+784 on a time span of nearly 6 years are presented and discussed. The optical light curve showed an overall variation greater than 3 mag, and the largest changes occured in…

About twenty years of radio observations in five bands (from 4.8 to 37 GHz) of the BL Lac object GC 0109+224 (S2 0109+22, RGB J0112+227), are presented and analysed together with the optical data. Over the past ten years this blazar has…

We present here the discovery of rapid, large amplitude intraday variability in the compact flat-spectrum radio quasar 1156+295. The detection of 40% flux density variations at 15 GHz on a timescale of only 2.7 hours was serendipitously…

The BLLac object S4 0954+65 is one of the main targets of the Urumqi monitoring program targeting IntraDay Variable (IDV) sources. Between August 2005 and December 2009, the source was included in 41 observing sessions, carried out at a…

With an aim to explore optical variability at diverse timescales in BL Lac source S5 0716+714, it was observed for 46 nights during 2013 January 14 to 2015 June 01 when it underwent two major outbursts. The observations were made using the…

We address the topic of the Intra-Night Optical Variability of the BL Lac object S5 0716+714. To this purpose a long term observational campaign was performed, from 1996 to 2003, which allowed the collection of a very large data set,…

We aim to search for evidence of annual modulation in the time scales of the BL Lac object S5 0716+714. The intra-day variability (IDV) observations were carried out monthly from 2005 to 2009, with the Urumqi 25m radio telescope at 4.8 GHz.…

Intraday variability (IDV) of compact extragalactic radio sources is a complex phenomenon and shows a wavelength dependent mixture of refractive interstellar scintillation (RISS) (dominant at long cm-wavelengths) and source-intrinsic…

We report rapid optical variability for the blazar S5 0716+71 during 2010 March 08-10 & 19-20 in the CCD observations made from Mt.Abu Infrared Observatory. The light curves are constructed for the duration longer than 3-hours each night,…

For a new sample of 8 weak-line-quasars (WLQs) we report a sensitive search in 20 intranight monitoring sessions, for blazar-like optical flux variations on hour-like and longer time scale (day/month/year$-$like). The sample consists…

We monitored the BL Lac object S5 0716+714 in the optical band during October 2008, December 2008 and February 2009 with a best temporal resolution of about 5 minutes in the BVRI bands. Four fast flares were observed with amplitudes ranging…

We selected a sample of a dozen blazars which are the prime candidates for simultaneous multi-wavelength observing campaigns in their outburst phase. We searched for optical outbursts, intra-day variability and short term variability in…

In this paper we present results of a short-term optical monitoring of 13 blazars. The objects were monitored mostly in the R-band for a total of ~ 160 hours between 2006 and 2011. We study the nature of the short-term variations and show…

Radio activity has been observed in a large variety of stellar objects, including in the last few years, ultra-cool dwarfs. To explore the extent of long-term radio activity in ultra-cool dwarfs, we use data taken over an extended period of…

Intraday Variability of compact extragalactic radio sources can be interpreted as quenched scintillation due to turbulent density fluctuations of the nearby ionized interstellar medium. We demonstrate that the statistical analysis of IDV…

We present flux-ratio curves of the fold and cusp (i.e. close multiple) images of six JVAS/CLASS gravitational lens systems. The data were obtained over a period of 8.5 months in 2001 with the Multi-Element Radio-Linked Interferometer…

Radio variability on timescales from a few hours to several days in extragalactic flat-spectrum radio sources is generally classified as intra-day variability (IDV). The origin of this short term variability is still controversial and both…

We present a study of the intraday variability behaviour of a complete sample of radio-selected BL Lac objects taken from the 1 Jy catalogue. In 28 out of 34 BL Lac objects (82\%) we detected intraday variability. 7 objects were observed…

The X-ray emission from blazars has been widely investigated using several space telescopes. In this work, we explored statistical properties of the X-ray variability in the blazars S5 0716+714, OJ 287, Mkn 501 and RBS 2070 using the…

We present the first unambiguous case of external variability of an extra-galactic radio source, the CLASS gravitational lens B1600+434, consisting of two images lensed by an edge-on disk galaxy. The VLA 8.5-GHz difference light curve of…