ELFT HÍRADÓ

[vidakris AT konkoly.hu]

Szemináriumi meghívó / Invitation to a seminar
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CSFK CSI SZEMINÁRIUM / KONKOLY OBSERVATORY SEMINAR

Date: Feb 26 (Thursday) 14:00


Angelina Osetrova
Institute of Applied Astronomy, St. Petersburg


Applications of geodetic VLBI in astrophysics and cosmology

Very Long Baseline Interferometry (VLBI) is a powerful technique which 
provides high-precision astrometric and high-resolution astrophysics 
observations. One of its key applications is the construction of a 
quasi-inertial celestial reference system, namely the International Celestial 
Reference System (ICRS), realized through VLBI observations of distant 
quasars, which are expected to have no physical proper motions and parallaxes 
due to large distances to them. The floor accuracy of current realization 
ICRF3 is limited to 30 µas while the uncertainty of position of individual 
radio sources ranges from 6 µas to several mas. This discrepancy is 
attributed to intrinsic astrometric instability of the sources and underlying 
systematic effects.

One of the such factors impacting the astrometric behavior of the sources 
could be the primordial gravitational waves, which appear as quadrupole 
systematics in proper motion of extragalactic radio sources. Moreover, 
recently, it was discovered that extragalactic radio sources have “negative 
parallaxes”, with a weighted mean value of −16.9 µas. While this effect lacks 
a definitive explanation, there are theoretical predictions that such the 
effect may occur due to the gravitational waves or ultralight scalar dark 
matter in the Solar System.

Overall, detected systematic effects may be a manifestation of several 
cosmological and astrophysical phenomena and need to be studied as it may 
provide a novel avenue to explore gravitational physics, dark matter models.


https://konkoly.hu/k-szeminariumok

The seminar will be held live in the Detre hall with audience, but also 
streamed online via Zoom. If you are unable to attend the presentation in 
person, you can join us via this link
https://us06web.zoom.us/j/82806911982?pwd=SVZpT0syQ1J6dHBvSkF4N2dXNEQ0dz09
or the meeting ID: 828 0691 1982 and passcode: 206265



Everyone is welcome!

Krisztián Vida, Mina Ghodsi
organizers
https://konkoly.hu/k-szeminariumok