VLBI - Connecting Astronomers Worldwide
The EVN presents a series of virtual seminars focused on how very long baseline interferometry (VLBI) observations can significantly contribute to different astronomical fields. These seminars are oriented to the broad astronomical community and provide an engaging introduction to cutting-edge research from different groups across the world.
A series of talks, covering different science topics with different speakers. Discover with us these passionate fields.
The seminars will have a duration of 40 minutes (plus around 20 minutes of questions and discussion), and can be joined by Zoom or watched in streaming in YouTube. Note that the Zoom capacity is 100 participants. Once the limit is reached we will refer to the YouTube streaming. The videos will be recorded and published at the JIVE/EVN YouTube channel and could be watched at any time.
The EVN seminars will be resumed soon. Just stay tuned!
Watch the Past Seminars
Intermediate-mass black holes in the era of radio astronomy
Institute of Space Sciences (ICE-CSIC)
Thursday 5 May 2022 10:00 CEST
Black holes of 100–100,000 solar masses formed at redshifts of z < 20 are currently the best candidates to being the seeds of the first supermassive black holes that power the quasars detected at z ~ 6–7. Studying this population of high-redshift seeds has so far only been possible by investigating the possible local relics of those that did not become supermassive, which can be found in the local Universe as intermediate-mass black holes (IMBHs) in dwarf galaxies. I will show how radio interferometric observations have been key to identify and characterize actively accreting IMBHs in the local Universe and out to z ~ 3. The next generation of radio telescopes such as the SKA will open a new window on detecting seed black holes at birth, probing the formation pathways of the first quasars in the Universe.
Exploring the lowest mass objects at the highest angular resolution: low-mass stars, ultracool dwarfs and exoplanets
Juan B. Climent
University of Valencia
Monday 14 March 2022 - 16:00 CET
At the very low mass regime of stellar and substellar objects, ultra-cool dwarfs (UCDs) cover the boundary between stars and exoplanets where radio observations have already proved the existence of powerful magnetic fields. Such observations are crucial not only to directly measure the strength and topology of the UCDs’ magnetic fields but also for opening a new route for the detection of exoplanetary radio emission, and hence, establishing a novel tool to discover new worlds. The great utility of radio observations is amplified in the case of binary systems as sub-mas astrometry can determine the dynamical masses. Despite this great potential, only a handful of VLBI observations of UCDs have been successful. In this talk, we will discuss the current state of the scientific knowledge regarding these topics while sharing our contributions: (i) multi-epoch multi-wavelength observations of a substellar triple system; (ii) new radio detections in several UCDs, including three binary low-mass systems, and, remarkably, a T6-object; and (iii) the sub-mas morphology of UCDs displaying auroral radio emission.
High resolution observations of magnetic fields in the Central Molecular Zone of the Galactic Center
Cornelia C. Lang
University of Iowa
Friday 28 January 2022 - 16:00 CET
In addition to harboring a supermassive black hole at its very core, the Galactic center is one of the most physically extreme environments in the Galaxy. Dense and massive molecular clouds on non-circular orbits are abundant in this region, yet star formation is not as active and frequent as expected. In addition, radio observations have revealed a population of synchrotron-emitting filaments that provide insight on the magnetic field strength and configuration in this unique region of the Galaxy. I will review observational results from several recent studies undertaken by my research group: we have examined the properties and kinematics of a group of unusual molecular clouds that appear to be part of an orbital “stream” of material around the Galactic center. In addition, we have been studying the detailed structure of the synchrotron-emitting radio filaments and their connection to larger-scale energetic outflows from the Galactic center. Our relative proximity to the Galactic center provides an unprecedented view of a galactic core and studies of this region can be used as an astrophysical analog to understanding the nuclei of more distant galaxies.
Observing interplanetary spacecraft with radio telescopes: connecting astronomers and space scientists
Joint Institute for VLBI ERIC
Monday 29 November 2021 - 16:00 CET
Observations of human-made satellites using arrays of radio telescopes can provide the ultra-precise determination of their speed and their position on the celestial sphere. The Planetary Radio Interferometry and Doppler Experiment (PRIDE) is a technique that connects ground-based radio astronomy and space science to deliver the sharpest view of spacecraft in our solar system. PRIDE's precise determination of the lateral position of spacecraft can be used for a variety of scientific applications, including improvement of ephemerides, ultra-precise celestial mechanics of planetary systems, gravimetry, spacecraft orbit determination, and fundamental physics. Furthermore, observations of the radio signal transmitted by a spacecraft are an important source of information on interplanetary plasma and solar wind. In this talk, I will present novel results of observing ESA and NASA spacecraft with ground-based radio telescopes and demonstrate the capabilities of such a technique.
Tying the Sky to the Ground
University of Valencia
Friday 9 July 2021 - 15:00 CEST
The technique of Astronomical Interferometry allows us achieve the highest spatial resolutions in the observation of the Universe, thanks to the perfect coordination of different radiotelescopes spread across the Earth's surface. Besides the unbeatable spatial resolution, interferometry can also be used to estimate the locations of the sources on the sky, as well as the relative positions of the radiotelescopes, with precisions of a few tens of micro-arcseconds in the former and a few millimeters in the latter. In this talk, we will discuss about the use of interferometry techniques for high-precision Astrometry and Geodesy. We will review some key results and talk about on-going and future projects.
X-ray binaries unveiled by very high resolution radio imaging
Wednesday 9 June 2021 - 10:00 CEST
Accreting X-ray binaries are excellent laboratories to study extreme physics in our universe and provide unique opportunities to understand exotic neutron stars and black holes. It is thought that black hole X-ray binaries are small-scale Active Galactic Nuclei whose radio jets vary on human timescales. High-resolution radio imaging and astrometry are powerful tools that allow us to directly probe into the evolution of these jets. In this talk, I will review the study of compact X-ray binaries and how Very Long Baseline Interferometry is enabling exciting breakthroughs in understanding their birth, evolution and advancing the search for new X-ray binary systems.
Re-solving multi-messenger puzzles with Very Long Baseline Interferometry
INAF Instituto di Radioastronomia
Wednesday 19 May 2021 - 10:00 CEST
The detection of information carried by means other than electromagnetic waves has opened a new era in the study of the Universe. Very Long Baseline Interferometry, thanks to its exquisite angular resolution, remains the only technique allowing astronomers to directly image the most compact structures associated with the emission of energetic photons or other carriers of information, as well as their evolution. An outstanding example was the observation of the formation of a jet following the first - and so far unique - concurrent detection of gravitational and electromagnetic waves in GW 170817. In this talk, I will review the observational and astrophysical novelty of the VLBI campaign following this event, and the prospects for future synergies between VLBI and multi-messenger observations in the field of transient astrophysical sources.
Shadows and Photon Rings: Imaging Supermassive Black Holes with the Event Horizon Telescope
Harvard-Smithsonian Center for Astrophysics
Monday 29 March 2021 - 16:00 CEST
The Event Horizon Telescope (EHT) uses very long baseline interferometry (VLBI) at 1.3-mm wavelength to produce images of supermassive black holes with horizon-scale resolution. I will discuss the breakthroughs that made these images possible and their implications for our understanding of supermassive black holes. I will also describe the emerging capabilities of the EHT to study relativistic dynamics of accretion flows and to elucidate the role of magnetic fields in jet launching. Finally, I will discuss the complex, fractal structure that is predicted to appear in higher resolution images of black holes, which enables a new type of radio interferometer capable of precision tests of General Relativity.
Distance of optically-obscured evolved stars
Jodrell Bank Centre for Astrophysics & University of Manchester
Friday 5 February 2021 - 15:00 CET
As intermediate-mass stars head towards their final fate, they pass through the red-giant stage where they experience an increase of mass loss. This induces the creation of a circumstellar envelope of dust and gas. By the very end of this evolutionary stage, the amount of dust in the circumstellar envelope of a good fraction of these evolved stars is such that it blocks optical radiation, turning them into so-called OH/IR stars. These precursors of planetary nebulae are commonly observed throughout the Galaxy and are also observed in the Magellanic Clouds. Since optically thick, measurements of their distances using optical parallaxes as e.g. delivered by GAIA, is not possible. This issue can be circumvented thanks to maser emission. As their name gives it away, the physical conditions turn out to be ideal for a strong (1612-MHz) OH maser emission to be produced in the outer layers of the radially-expanding spherical circumstellar envelope of OH/IR stars. I will present how, combining single-dish monitoring and interferometric mapping of this OH maser emission, the "phase-lag method" allows us to measure their distance.
Galactic Maser Astrometry with Very Long Baseline Interferometry: Current Status and Beyond
National Astronomical Observatory of Japan
Wednesday 9 December 2020 - 10:00 CET
I will present the most recent results of high-resolution maser astrometry with Very Long Baseline Interferometry (VLBI). Maser astrometric surveys have been conducted with the Japanese VERA array and the Bar and Spiral Structure Legacy (BeSSeL) project, aimed at exploring the dynamic structure of the Milky Way. I will present recent results from these surveys, mainly covering topics on the determination of fundamental parameters, rotation curve measurement, tracing spiral structures, comparisons/calibrations of GAIA astrometry, and so on. I will also cover some topics related to individual maser sources (star forming regions and AGB stars) revealed by VLBI astrometry in combination with other arrays such as the Atacama Large Millimeter Array (ALMA). Finally, I will briefly discuss the future prospects of VLBI astrometry for forthcoming global VLBI in the SKA era.
Pin-pointing the positions of repeating Fast Radio Bursts
University of Amsterdam & ASTRON
Monday 19 October 2020 - 16:00 CEST
Fast radio bursts (FRBs) are bright pulses of coherent radio emission with durations of only a few milliseconds, and unknown extragalactic origin. Some FRBs have been observed to repeat, whereas others appear as one-off events. Currently it still remains unclear whether all FRB sources have the ability to repeat, or if there are multiple populations with different physical mechanisms. Recently, the Galactic magnetar SGR 1935+2154 emitted a very bright radio burst (orders of magnitude brighter than typical Galactic radio bursts from pulsars/magnetars) unveiling a bridge between Galactic sources of radio bursts and FRBs. With the European VLBI Network (EVN) we can precisely localise FRBs to milli-arcsecond precision, identifying not only the host galaxy, but the region within the host that the bursts are originating from. This will help in understanding the FRB progenitor(s) and how FRBs link to Galactic sources. In addition to the real-time correlation observing mode (e-EVN), baseband data can be buffered to study fine time and frequency structures of the bursts, as well as their polarisation properties. In this talk I will discuss our approach to localising repeating FRBs using the EVN, present the localisation of a second repeater, FRB 180619.J0158+65, and present recent results on SGR 1935+2154.
VLBI as a key to the origin of high-energy neutrinos
Astro Space Center
Friday 4 September 2020 - 14:00 CEST
Observational information on high-energy astrophysical neutrinos is being continuously collected by the IceCube observatory. However, the sources of the neutrinos are still unknown. We studied a large complete VLBI-selected sample of extragalactic radio sources and found that AGN positionally associated with IceCube events have typically stronger parsec-scale cores. Moreover, we see an increase of radio emission at frequencies above 10 GHz around neutrino arrival times. We conclude that AGNs with bright Doppler-boosted jets observed at small viewing angles constitute an important population of neutrino sources. High-energy neutrinos are produced in their central parsec-scale regions, probably in proton-photon interactions.
Using Strong Gravitational Lensing to Zoom in on High-Redshift Galaxies
University of Bologna & INAF Istituto di Radioastronomia
Wednesday 8 July 2020 - 10:30 CEST
The centres of galaxies are powerful laboratories to test models of galaxy formation, as well as the interplay between supermassive black holes and their host galaxies. While these sub-galactic scales can be directly investigated in the local Universe, it is observationally extremely difficult to access them at high redshift. In this talk, we will exploit the combination of strong gravitational lensing and multi-wavelength high angular resolution observations to directly study the parsec scale emission in active galaxies at z > 1. The magnifying effect of strong lensing and the milliarcsecond angular resolution of HST, Keck AO and VLBI observations allow us to spatially resolve the central parts of distant lensed galaxies, especially if they are located in the regions at highest magnification. Therefore, it becomes possible to unveil dual and offset AGN candidates, but also faint extended jets embedded in massive molecular gas reservoirs at cosmological distances. Nevertheless, this kind of study is currently limited by the small number of radio-loud lensed sources. We will conclude by discussing the current efforts to search for more lensing systems in wide-field VLBI surveys.
Torun Institute of Astronomy, Nicolaus Copernicus University
Joint Institute for VLBI ERIC
Department of Physics, University College Cork
INAF Istituto di Radioastronomia
Instituto de Astrofísica de Andalucía - CSIC