Related papers: VLTI-GRAVITY observations of blazars

The Fermi gamma-ray space telescope has revolutionized our view of the gamma-ray sky and the high energy processes in the Universe. While the number of known gamma-ray emitters has increased by orders of magnitude since the launch of Fermi,…

Here we report on the results of the WEBT photo-polarimetric campaign targeting the blazar S5~0716+71, organized in March 2014 to monitor the source simultaneously in BVRI and near IR filters. The campaign resulted in an unprecedented…

The new generation of VLTI instruments (GRAVITY, MATISSE) aims to produce routinely interferometric images to uncover the morphological complexity of different objects at high angular resolution. Image reconstruction is, however, not a…

The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed contemporaneously by the Very Long Baseline Array (VLBA). In total, 232 sources were observed with…

In November 2023, the Fermi Large Area Telescope detected a $\gamma$-ray flare from the high-redshift blazar GB6 B1428+4217 ($z=4.715$). We initiated a multi-wavelength follow-up campaign involving Swift, NuSTAR, the Sierra Nevada and…

Since mid-2007 we have carried out a dedicated long-term monitoring programme at 15 GHz using the Owens Valley Radio Observatory 40 meter telescope. One of the main goals of this programme is to study the relation between the radio and…

As part of the GRAVITY$^{+}$ project, the near-infrared beam combiner GRAVITY and the VLTI are currently undergoing a series of significant upgrades to further improve the performance and sky coverage. The instrumental changes will be…

Context. A new four-telescope interferometric instrument called PIONIER has recently been installed at VLTI. It provides improved imaging capabilities together with high precision. Aims. We search for low-mass companions around a few bright…

Fermi J1544-0649 is a transient GeV source first detected during its GeV flares in 2017. Multi-wavelength observations during the flaring time demonstrate variability and spectral energy distribution(SED) that are typical of a blazar. Other…

Comprehensive VLBI and multi-waveband monitoring indicate that a single superluminal knot can cause a number of gamma-ray flares at different locations. However, the often very rapid variability timescale is a challenge to theoretical…

Using millimeter-very long baseline interferometry (VLBI) observations of the BL Lac object S5 0716+714 from August 2008 to September 2013, we investigate variations in the core flux density and orientation of the sub-parsec scale jet i.e.…

Blazars are active galactic nuclei with relativistic jets pointed almost directly at Earth. Blazars are characterized by strong, apparently stochastic flux variability at virtually all observed wavelengths and timescales, from minutes to…

The Fermi, Swift and INTEGRAL satellites, together with ground based (especially Cherenkov) telescopes made possible a great progress in our understanding of relativistic jets. We can now start to attack the difficult questions of jet…

The paper investigates the milli-arcsecond scale structure of the present-day mass-loss of the post-Red Supergiant IRC+10420. We use three telescopes of the VLT Interferometer in combination with the AMBER near-infrared beam combiner to…

Relativistic amplification boosts the contribution of the jet base to the total emission in blazars, thus making single dish observations useful and practical to characterise their physical state, particularly during episodes of enhanced…

The gamma-ray emission offers a powerful diagnostic tool to probe jets and their surroundings in flat spectrum radio quasars (FSRQ). In particular, sources emitting at high energies (>10 GeV) give us the strongest constraints. This…

The TANAMI (Tracking AGN with Austral Milliarcsecond Interferometry) and associated programs provide comprehensive radio monitoring of extragalactic gamma-ray sources south of declination -30 degrees. Joint quasi-simultaneous observations…

Blazar spectra are one of the most important windows into the physical processes occurring along jets. The spectrum, composed from the different emitting regions along the jet, allows us to constrain the physical conditions in the jet. I…

We perform a multi-wavelength polarimetric study of the quasar CTA 102 during an extraordinarily bright $\gamma$-ray outburst detected by the {\it Fermi} Large Area Telescope in September-October 2012 when the source reached a flux of…

The galactic central black hole Sgr A* exhibits outbursts of radiation in the near infrared (so-called IR flares). One model of these events consists in a hotspot orbiting on the innermost stable circular orbit (ISCO) of the hole. These…