Related papers: Multi-band optical micro-variability observations …

The long-term optical and infrared color variability of blazars has been investigated with the SMARTS monitoring data. The sample in this study consists of 49 flat spectrum radio quasars and 22 BL Lac objects. The fractional variability…

In an optical monitoring program to characterize the variability properties of blazar, we observed 10 sources from the Roma-BZCAT catalogue for 26 nights in V and R bands during October 2014 to June 2015 with two telescopes located 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…

Context. We present the light curves of six BL Lac objects, PKS 0537-441, PKS 0735+17, OJ 287, PKS 2005-489, PKS 2155-304, W Comae, and of the flat spectrum radio quasar PKS 1510-089, as a part of a photometric monitoring program in the…

We present the results of an extensive analysis of the optical, ultraviolet, X-ray and $\gamma$-ray data collected from the observations of the BL Lac objects prototype BL Lacertae carried out over a period of nearly 13 years, between…

BL Lac has been observed during the outburst occurred in the 1997 summer (Noble et al. 1997; Bloom et al. 1997) in three optical bands (BVI), with the aim of studying the intranight colour variations on very short timescales. Due to the…

We present the results of the first systematic long-term multi-color optical monitoring of the BL Lacertae object 1ES 0806+52.4. The monitoring was performed in multiple passbands with a 60/90 cm Schmidt telescope from December 2005 to…

Since 1997, BL Lacertae has undergone a phase of high optical activity, with the occurrence of several prominent outbursts. Starting from 1999, the Whole Earth Blazar Telescope (WEBT) consortium has organized various multifrequency…

Aims: Intranight variation (or microvariation) is a common phenomenon of radio-loud BL Lac objects. However, it is not clear whether the recently found radio-quiet BL Lac objects have the same properties. The occurrence rate of intranight…

We have organized an extensive multiwavelength campaign on BL Lacertae in the second half of 2000. Simultaneous or quasi-simultaneous observations were taken at radio frequencies, in the optical - carried out by the WEBT collaboration -, in…

BL Lacertae has been the target of several observing campaigns by the Whole Earth Blazar Telescope (WEBT) collaboration and is one of the best studied blazars at all accessible wavelengths. A recent analysis of the optical and radio…

We present the most continuous data base of optical $BVR_{c}I_{c}$ observations ever published on the BL Lacertae object GC 0109+224, collected mainly by the robotic telescope of the Perugia University Observatory in the period November…

We present photometric observations of the BL Lacertae object S5 0716+714 with a temporal resolution of 120 s in the Sloan i' and r' bands. These observations were conducted using the Comet Search Program telescope at Xingming Observatory…

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 present the results of our optical monitoring of the BL Lacertae object OJ 287 during the first half of 2005. The source did not show large-amplitude variations during this period and was in a relatively quiescent state. A possible…

We carried out a pilot campaign of radio and optical band intra-day variability (IDV) observations of five blazars (3C66A, S5 0716+714, OJ287, B0925+504, and BL Lacertae) on December 18--21, 2015 by using the radio telescope in Effelsberg…

We present UBVRI light curves of BL Lacertae from May 2000 to January 2001, obtained by 24 telescopes in 11 countries. More than 15000 observations were performed in that period, which was the extension of the Whole Earth Blazar Telescope…

We carried out multi-color optical monitoring of a sample of ten blazars from 2005 to 2011. The sample contains 3 LBLs, 2 IBLs, 4 HBLs, and 1 FSRQ. Our monitoring focused on the long-term variability and the sample included nine BL Lac…

BL Lacertae has been the target of four observing campaigns by the Whole Earth Blazar Telescope (WEBT) collaboration. In this paper we present $UBVRI$ light curves obtained by the WEBT from 1994 to 2002, including the last, extended BL Lac…

BL Lacertae is not only archetypical of an entire class of jet-dominated active galactic nuclei, blazars, but also one of the most active and rapidly changing objects in this class. In the fall of 2024 (September--November), BL Lacertae…