Active galactic nuclei with flat radio spectra exhibit significant variations of continuum flux
density on time scales of days or less throughout the entire wavelength range. These rapid …

Relativistic jets of active galactic nuclei have been known to exist for 100 years. Blazars with
their jet pointing close to our line of sight are some of the most variable and extreme objects …

Context. Gaia has been in operations since 2014, and two full data releases (DR) have been
delivered so far: DR1 in 2016 and DR2 in 2018. The third Gaia data release expands from …

Context. Gaia DR3 contains 1.8 billion sources with G-band photometry, 1.5 billion of which
with G BP and G RP photometry, complemented by positions on the sky, parallax, and …

Several years after its initial identification (Balick & Brown 1974), the radio source at the
center of our Galaxy, now associated with the supermassive black hole Sagittarius A*(Sgr …

As telescopes, detectors, and computers grow ever more powerful, the volume of data at the
disposal of astronomers and astrophysicists will enter the petabyte domain, providing …

The second catalog of active galactic nuclei (AGNs) detected by the Fermi Large Area
Telescope (LAT) in two years of scientific operation is presented. The second LAT AGN …

This paper presents light curves as well as the first systematic characterization of variability
of the 106 objects in the high-confidence Fermi Large Area Telescope Bright AGN Sample …

The Gaia Galactic survey mission is designed and optimized to obtain astrometry,
photometry, and spectroscopy of nearly two billion stars in our Galaxy. Yet as an all-sky multi …

The most intense monitoring observations yet made in the optical and near-infrared wave
bands were carried out for Seyfert 1 galaxies NGC 5548, NGC 4051, NGC 3227, and NGC …