UBVRI observations of 37 QSOs are reported. The sample is considered as a good representation of the bright (V not greater than 17) quasars in the compilation...
Unprecedented study of the broadband emission of Mrk 421 during flaring activity in March 2010
Context. Because of its proximity, Mrk 421 is one of the best sources on which to study the nature of BL Lac objects. Its proximity allows us to characterize...
Unraveling the Complex Behavior of Mrk 421 with Simultaneous X-Ray and VHE Observations during an Extreme Flaring Activity in 2013 April
We report on a multiband variability and correlation study of the TeV blazar Mrk 421 during an exceptional flaring activity observed from 2013 April 11 to 19...
Variability and evolution of the optical polarization of a sample of gamma-ray blazars
We present a polarization variability analysis of a sample of 26 γ-ray blazars monitored by the Steward Observatory between 2008 and 2018 in the optical band...
Variable Very High Energy γ-Ray Emission from Markarian 501
The blazar Mrk 501 was observed at energies above 0.10 TeV with the MAGIC Telescope from 2005 May through July. The high sensitivity of the instrument enabled...
Visible and near-infrared monitoring of 3C279 in 1988-89
Near infrared monitoring taken with the 1.5 m Carlos Sanchez Telescope in Tenerife of the decline of 3C279 during its 1988 outburst is presented. These data are...
We report here the first results of a program aimed at obtaining high signal to noise (up to ~ 500) optical spectroscopy of a large sample of BL Lac objects...
What Is the Redshift of the Gamma-ray BL Lac Source S4 0954+65?
High signal-to-noise ratio spectroscopic observations of the BL Lac object S4 0954+65 at the alleged redshift z = 0.367 are presented. This source was detected...