Related papers: B2 1308+326: a changing-look blazar or not?

We present the results of six BeppoSAX observations of 1ES 2344+514, five of which were taken within a week. 1ES 2344+514, one of the few known TeV BL Lac objects, was detected by the BeppoSAX Narrow Field Instruments between 0.1 to \~50…

We present the results of a multi-frequency, time-averaged analysis of blazars included in the Candidate Gamma-ray Blazar Survey catalog. Our sample consists of 324 $\gamma$-ray detected ($\gamma$-ray loud) and 191 non $\gamma$-ray detected…

To search for optical variability on a wide range of timescales, we have carried out photometric monitoring of two flat spectrum radio quasars, 3C 454.3 and 3C 279, plus one BL Lac, S5 0716+714, all of which have been exhibiting remarkably…

We monitored BL Lacertae in the B, V, R and I bands for 14 nights during the period of 2016-2018. The source showed significant intraday variability on 12 nights. We performed colour-magnitude analysis and found that the source exhibited…

We report the first detection at 4.7 and 8.2 GHz with the RATAN-600 radio telescope of the source PSO J047.4478+27.2992, which has been announced as a blazar at z=6.1. The average flux density is $12\pm3$ and $8\pm4$ mJy at 4.7 and 8.2 GHz…

The MAGIC telescopes observed S2 0109+22 in 2015 July during its flaring activity in high energy gamma rays observed by Fermi-LAT. We analyse the MAGIC data to characterise the very high energy (VHE) gamma-ray emission of S2 0109+22, which…

Optical monitoring of S5 0716+714 was performed with a 60/90 Schmidt telescope in 2003 November and December and 2004 January for studying the variability of the object on short timescales. Due to the high brightness of the source we could…

"Changing-look quasars" (CLQs) are active galactic nuclei (AGN) showing extreme variability that results in a transition from Type 1 to Type 2. The short timescales of these transitions present a challenge to the unified model of AGN and…

We present a detailed temporal and spectral study of the blazar 3C\,279 using multi-wavelength observations from Swift-XRT, Swift-UVOT and Fermi-LAT during a flare in 2018 January. The temporal analysis of $\gamma$-ray light curve indicates…

We analyzed the multi-band optical behaviour of the BL Lacertae object, S5 0716+714, during its outburst state from 2014 November - 2015 March. We took data on 23 nights at three observatories, one in India and two in Bulgaria, making…

We present and analyse new R-band frames of the gravitationally lensed double quasar FBQ 0951+2635. These images were obtained with the 1.5m AZT-22 Telescope at Maidanak (Uzbekistan) in the 2001-2006 period. Previous results in the R band…

The gamma-ray blazar 3C 279 was monitored on a nearly daily basis with IUE, ROSAT and EGRET for three weeks between December 1992 and January 1993. During this period, the blazar was at a historical minimum at all wavelengths. Here we…

The BL Lacertae object S50716+714 is one of the most studied blazars on the sky due to its active variability and brightness in many bands, including VHE gamma rays. We present here two serendipitous results from recent far-ultraviolet…

We present a comprehensive 20-year multiwavelength variability study of the blazar PKS 2155-304, one of the most luminous and extensively monitored high-frequency-peaked BL Lac objects in the southern hemisphere. Using Fermi-LAT…

We have monitored the BL Lacertae object S5 0716+714 in the optical bands during 2012 January and February with long time spans on intraday timescales ($>$5 hr) and high time resolutions. During this monitoring period, the object shows…

In October 2024, the object BL Lacertae experienced the brightest flaring event in gamma-ray ($>$100 MeV) with a historically bright $\gamma$-ray flux of $\sim$2.59 $\times 10^{-5}$ erg cm$^{-2}$ s$^{-1}$ with a detection of a 175.7 GeV…

Eight optical and four radio observatories have been intensively monitoring the BL Lac object 0716+714 in the last years: 4854 data points have been collected in the UBVRI bands since 1994, while radio light curves extend back to 1978. Many…

BL Lac has entered an active state since 2020, with multiwavelength observations revealing intense flares. In this study, we conducted 12-night multicolor optical monitoring using an 85 cm telescope from 2020 September to 2024 June and…

PSR B0823+26, a 0.53-s radio pulsar, displays a host of emission phenomena over timescales of seconds to (at least) hours, including nulling, subpulse drifting, and mode-changing. Studying pulsars like PSR B0823+26 provides further insight…

Blazars are known for their variability on a wide range of timescales at all wavelengths. Most studies of TeV gamma-ray blazars focus on short timescales, especially during flares. With a decade of observations from the Fermi-LAT and…