We present an optical spectrum (λλ4000-10 500) of the lensed blazar B0218+357 secured at the 10 m GTC and aimed to investigate and clarify the properties of...

We present ALMA Atacama Compact Array (ACA) 870 μm continuum maps of 28 infrared-bright SDSS quasars with Herschel/SPIRE detections at redshifts 2-4, the...

We present optical spectra for a representative sample of 27 nearby (z 0.2) Two Micron All Sky Survey (2MASS)-selected active galactic nuclei (AGN) with red...

We investigate the relation between the radio (Fr) and optical (Fo) flux densities of a variety of classes of radio transients and variables, with the aim of...

Although the QSO PKS 2128 - 123 appears as highly variable in the I band, with Delta-I of up to 1.69 mag, it is a moderate amplitude variable object in the...

The flat-spectrum radio quasar PKS 1222+216 (4C+21.35, z = 0.432) was detected in the very high energy γ-ray band by MAGIC during a highly active γ-ray phase...

We report results of a spectroscopic campaign carried out at the 10 m Gran Telescopio Canarias for a sample of 22 BL Lac objects detected (or candidates) at TeV...

Microvariations probe the physics and internal structure of quasars. Unpredictability and small flux variations make this phenomenon elusive and difficult to...

In this paper we present photometric redshift estimates for a sample of X-ray selected sources detected in the wide-field ( 2 deg^2), bright [ f_X(0.5{-}8 keV)...