Very Long Baseline Interferometry (VLBI) is a space-geodetic technique directly connecting the Terrestrial Reference Frame realized by positions of Earth-based stations with the Celestial Reference Frame (CRF) defined by a set of extragalactic radio sources (quasars) well distributed throughout the sky. Due to the rotation of the Solar System Barycentre (SSB) around the centre of Milky Way galaxy, the arising acceleration of the SSB induces an apparent proper motion of the extragalactic objects observed by VLBI, i.e., a change in the apparent source positions over time. The aberration amplitude estimates (5 - 7 microas/year) from geodetic VLBI are close to the independent estimates derived from astrometric measurements of proper motions and parallaxes of masers, and it is not negligible in terms of the upcoming ICRF3 catalogue anymore.
Seminars take place in the lecture room of the Spořilov building (see contacts) unless noted otherwise.
A primary target for gravitational wave astronomy is the detection of a stochastic background formed by the superposition of many unresolved independent sources at different stages of the evolution of the Universe. After the first observations of a gravitational wave from the merger of two black holes (BHs) or two neutron stars (NSs), the next big milestone could be the observation of the stochastic background created by the superposition of all the unresolved compact binary coalescences (CBCs). The observation of this background will be the opportunity to study the population of NSs and BHs at high redshift, complementing individual detections at close distances. In this talk, I will give an overview of the different sources and will present the data analysis methods used in the LIGO/Virgo collaboration to measure the GW stochastic background. I will also discuss how the future generation of detectors can be used to remove the astrophysical contribution in order to observe the signal of cosmological origin.
If you would like to give a seminar, please contact Georgios Loukes-Gerakopoulos or Vladimír Karas.