Related papers: BZBJ1058+5628: a new quasi-periodic BL Lac

The fascination with the blazar OJ 287 stems not only from its status as a prominent candidate for a close supermassive black hole (SMBH) binary, but also because of the thermal bremsstrahlung origin proposed for its giant optical…

The data for BL Lac object S5 0716+714 optical B, R and I bands are collected from November 10, 2017 to May 15, 2018. The raw data consists of 21396 quasi-simultaneous multi-band points, with 7132 data points for each band. To search for…

We present here the results of the analysis of the $\gamma$-ray blazar, 1ES 1215+303, over a 10-year period, from 2008 to 2017, measured at high energies (HE; 200 MeV $< E <$ 100 GeV) by the Fermi Large Area Telescope (LAT) and at very high…

The physical origin of quasi-periodic oscillations (QPOs) in blazars remains debated, with geometric and plasma-driven scenarios as the main competing interpretations. Discriminating between them requires probing variability beyond flux…

In order to search for the evidence of quasi-periodic oscillation (QPO) in blazar, multicolor optical observations of the BL Lacertae object S5 0716+714 were performed from 2005 to 2012. For $I$ band on March 19 2010 with low variability…

We present HAWK-I J-band light curves of five late-type T dwarfs (T6.5-T7.5) with a typical duration of four hours, and investigate the evidence for quasi-periodic photometric variability on intra-night timescales. Our photometry reaches…

We present results of a periodicity search of 20 intra-day variable optical light curves of the blazar S5 0716+714, selected from a database of 102 light curves spanning over three years. We use a wavelet analysis technique along with a…

Seventeen southern sky BL Lacs were observed in UBVRI using the CCD Camera on the 1.0m telescope at the South African Astronomical Observatory (SAAO) in Aug and Nov 1999. The analyses of all the seventeen sources are now complete, and are…

We present an in-depth and systematic variability study of a sample of 20 powerful blazars, including 12 BL Lacs and 8 flat spectrum radio quasars, applying various analysis tools such as flux distribution, symmetry analysis, and time…

We present the first Kepler monitoring of a strongly variable BL Lac, W2R1926+42. The light curve covers 181 days with ~0.2% errors, 30 minute sampling and >90% duty cycle, showing numerous delta I/I > 25% flares over timescales as short as…

We analyze X-ray light curves of the blazars Mrk 421, PKS 2155-304, and 3C 273 using observations by the Soft X-ray Telescope on board AstroSat and archival XMM-Newton data. We use light curves of length 30-90 ks each from 3-4 epochs for…

We present the results of our power spectral density analysis for the BL Lac object OJ\,287, utilizing the {\it Fermi}-LAT survey at high-energy $\gamma$-rays, {\it Swift}-XRT in X-rays, several ground-based telescopes and the {\it Kepler}…

We report a possible detection of an ~4.6-hour quasi-periodic oscillation (QPO) in the 0.3-10 keV emission of the high-energy peaked blazar PKS 2155-304 from a 64 ks observation by the XMM-Newton EPIC/pn detector. We identify a total…

The observation data of blazar 1ES 1426 + 42.8 were obtained using the 1.02 m optical telescope of Yunnan Observatories during $2021$ to $2023$. Intraday variability (IDV) is detected on seven nights. We use the turbulent model to…

The variability of the high-frequency peaked BL Lac object PKS 2155-304 is studied using almost 10 years of optical, X-ray and gamma-rays data. Publicly available data have been gathered and analyzed with the aim to characterize the…

We present results of a multi-epoch intra-night optical monitoring of eleven blazars consisting of six BL Lac objects and five radio core-dominated quasars (CDQs). These densely sampled and sensitive R-band CCD observations, carried out…

We report the discovery of a quasar, SDSS J125809.31+351943.0 (J1258), which brightened in optical for 4 mag from 1983 to 2015, which is one of the largest quasar brightening events so far. The history of optical photometry data of this…

BL Lacertae (BL Lac) objects at high redshifts ($z\geq 2$) are rarely detected. Through careful analysis of the SDSS spectrum, BZB J1450+5201 is confirmed to be a high-$z$ BL Lac object with $z\geq$ 2.471 by identifying the Ly$\alpha$ 1216…

The extremely luminous infrared galaxy (ELIRG), WISE J090924.01+000211.1 (hereafter; WISE J0909+0002, $z=1.87$) is an extraordinary object with a quasar aspect. This study performs monitoring observations of WISE J0909+0002 with the 105 cm…

In order to study short timescale optical variability of $\gamma$-ray blazar S5 0716+714, quasi-simultaneous spectroscopic and multi-band photometric observations were performed from 2018 November to 2019 March with the 2.4 m optical…