About the Center
Research activities of the CAC are oriented towards the fields of high-energy astrophysics and experimental astroparticle and particle physics. The research is being to a large extent pursued through large international scientific collaborations.
Since 1999 we are involved in the Pierre Auger Collaboration, which explores the existence of ultra-high energy cosmic rays (UHECR). Their identities and sources are as yet unknown, and, at the highest energies, less than one particle per millennium hits a square kilometer of the Earth’s surface, so the UHECR can only be detected through their interaction with the Earth’s atmosphere. In collision with molecules of air they create extensive air showers of charged energetic particles that almost simultaneously hit the ground, covering an area of tens of square kilometers. To detect them the Pierre Auger Collaboration operates a vast UHECR observatory stretching over some 3000 square kilometers of pampa in Argentina’s Mendoza province and that is capable of measuring incoming directions, rates and energies of the UHECRs. Our center is involved in data analysis and interpretation, development and management of atmospheric monitoring sites, development of the distributed GRID computing system and studies of the effect of the galactic magnetic field on the UHECR trajectories.
High energy gamma rays, with energies from 100 GeV to 100 TeV can be detected through the Cherenkov light cosmic ray showers they initiate when hitting the atmosphere. Gamma ray astronomy with Cherenkov telescopes has been established for many years starting with the WHIPPLE telescope in 1968, extending to the current H.E.S.S., VERITAS and MAGIC telescopes. The CTA represents the common effort of this large community to build a next generation, full kilometer square array of Cherenkov telescopes, with the ability to reach sensitivities more than on order of magnitude improved over the current ones. The physics program of CTA includes high energy astrophysics, Cosmology and Fundamental Physics. The UNG has been involved in the CTA collaboration since 2013.
The Fermi LAT is the main instrument on the Fermi gamma ray spacecraft, launched from the Cape Canaveral Air Force Station on June 11, 2008. It detects gamma rays in the energy range of 20 MeV to above 300 GeV, scanning the entire sky every three hours. It has a better angular resolution, a wider field of view, and covers a broader energy range than its predecessor EGRET, which ended its mission in 2000. The Fermi LAT made many scientific breakthroughs including the discovery of over a thousand Active Galactic Nuclei and hundreds of pulsars, it mapped with exquisite precision the diffuse gamma ray emission coming from cosmic rays trapped in our Galaxy and set one of the most constraining limits on the models of dark matter particles. G. Zaharijas is a member of the Fermi LAT collaboration since 2008.
Gamma Ray Bursts (GRBs) are the most violent explosions in the Universe since the Big Bang. They are unpredictable and short (lasting in gamma rays ~0.01-1000 s), and followed in longer wavelengths by rapidly fading afterglows. GRBs are thought to be produced in two ways: by core collapse of a massive, rapidly rotating star, and by a merger of two neutron stars and/or black holes. Prof. Dr. Andreja Gomboc is studying GRBs since 2004 in collaboration with astronomers at Astrophysics Research Institute (Liverpool John Moores University), University of Bath, Universita degli Studi di Ferrara and INAF Osservatorio Astronomico di Brera. Prof. Gomboc’s main observing tool is the robotic Liverpool Telescope at Observatorio del Roque de los Muchachos on Canary Island La Palma.
Modern wide-field-of-view and all-sky satellites (e.g. Swift, Gaia) and ground based surveys (with optical and radio telescopes) cover a large part of the sky and are daily detecting new, transient sources of electro-magnetic radiation in the sky. While some transients are easily identified and well studied, others are observationally much more challenging due to their short duration and are consequently not well understood. Some of detected transients were identified as long-awaited flares from tidal disruption of a star by a massive black hole in a galactic centre. At UNG tidal disruption by black holes is studied by Prof. Dr. Andreja Gomboc and young researcher and PhD student Aurora Clerici, who are members of the Gaia Science Alerts Working Group.
Recently a new window to observe the Universe and detect transient events opened with the LIGO’s detection of gravitational waves from merging binary black holes. Prof. Dr. Andreja Gomboc is a member of international collaboration, which is responding to LIGO triggers and searching for electro-magnetic counterparts of gravitational wave events.
Center for Astrophysics and Cosmology is also involved in a collaboration with the Japanese Organization for Accelerator Research (KEK) since 1999 where, within the framework of Belle and Belle2 collaborations, we are investigating the differences between properties of particles and anti-particles called B mesons. Our results indicate a discrepancy between measured and theoretically predicted values of the so called CP asymmetry, which may be due to the existence of additional, yet undiscovered CP violating processes not present in the Standard model of elementary particle physics. The search for such processes is crucial for the understanding of the evolution of the universe and its current properties.