A new distinction for FORTH comes from the European Research Council (ERC) which approved the research program submitted by Dr. Andreas Zezas, researcher of the Astrophysics Group at the Institute of Electronic Structure and LASER (IESL) of FORTH. The approved program is entitled: "Accreting binary populations in Nearby Galaxies: Observations and Simulations” (A-BINGOS), and was submitted in the first ERC "Consolidator Grants” call. The goal of the ERC Consolidator Grants is to "enable already independent excellent researchers to consolidate their own research teams and to develop their most innovative ideas". In this call were approved 312 programs out of 3637 submitted proposals (a success rate of 8.5%). The program A-BINGOS is one of the only 2 programs awarded to Greek Institutions, and the first one to be awarded to a Greek Astrophysicist.

More specifically, the program A-BINGOS refers to accreting binaries: binary stellar systems in which the remnant of a massive star (black hole, neutron star, or a white dwarf) accretes material from another companion star. Since their discovery 50 years ago, accreting binaries have been an indispensable tool for the study of stellar remnants, their interplay with their companion stars and surrounding medium, as well as fundamental Physics (e.g. Einstein’s theory of General Relativity), and the behaviour of matter in extreme conditions (e.g. strong gravitational and magnetic fields).

Observational and theoretical studies of accreting binaries in our own Galaxy have helped to establish a basic framework for their formation and evolution. However, this framework is far from complete, partly due to the lack of observational constraints from the restricted population of accreting binaries in our Galaxy. In fact, recent studies in nearby galaxies revealed rare types of accreting binaries that are not present in our Galaxy, which led to the discovery of new pathways for the evolution of black holes in stellar systems.

The goal of the A-BINGOS program is to combine state-of-the-art observations of carefully selected samples of nearby galaxies, with evolutionary models for accreting binaries in order to test and complete the existing framework for their formation and evolution. The observational data used in this program consist of sensitive measurements of the X-ray emission from accreting binary systems in nearby galaxies with NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton Observatory. Since the X-ray emission is produced by the heated gas that is accreted onto the black hole or the neutron star, these observations will be used to identify the accreting binaries in these galaxies and obtain information about the stellar remnants they contain.

In addition to these X-ray observations, this program will employ a wealth of data in optical, ultraviolet (UV), and infrared (IR) wavelengths, mainly from the Hubble and other Space Telescopes, as well as Skinakas Observatory. These observations will be used to characterize the accreting binaries, and in particular to measure the age of their companion star. This way we will have a complete picture of the properties of the accreting binary, which will be compared with those expected based on our existing framework for their evolution. Any differences that will emerge from the results of this program will require the investigation of new evolutionary pathways, which are very likely in other galaxies with stellar populations of different ages or metal content than our own Galaxy.

These multi-wavelength data will also provide crucial information regarding the evolutionary history of the investigated galaxies, which will be used to directly link the accreting binaries with their parent stellar populations, and measure the formation efficiency of the latter, one of the key unknown factors in the present framework of their formation and evolution.

In conclusion, the goal of this program is to provide a comprehensive understanding of how the remnants of massive stars (black holes, neutron stars) form, and how they evolve when they are in binary stellar systems. This is of key importance for several areas of Physics and Astrophysics related to the formation and evolution of accreting binaries, and ranging from understanding the nature of the progenitors of the most violent explosions in the Universe (the g-ray bursts) and the sources of the gravitational waves (predicted from the theory of General Relativity and anticipated to be detected for the first time in the next decade), to the formation of the first galaxies.

For more information please contact:
Dr. Andreas Zezas
Researcher at IESL / FORTH
Tel.: 2810 394212
Email: azezas@physics.uoc.gr