The European Week of Astronomy and Space Science 2013

Symposium "The physics of accretion on compact objects: a multi-messenger approach"

July 8-9, 2013

Compact objects such as black holes (BH) and neutron stars (NS) represent the most extreme forms of matter available in the Universe. They are unique laboratories to study the physics under extreme conditions unachievable in Earth laboratories: strong gravity, super-strong magnetic fields, high radiation energy density and supra-nuclear densities. Accreting compact objects produce photons covering all the electromagnetic spectrum from the radio to the gamma-rays. The X-ray radiation is strongly variable at millisecond timescales, proving that it is produced in the very vicinity of the compact objects. Thus it carries the information about the motion of matter in strong gravitational field and can be used to measure the spin of the BHs, the masses and radii of NSs and thus to constrain the equation of state of cold dense matter.

Among the topics of major importance for (weakly magnetized) neutron stars are the physics of boundary/spreading layer and the origin of quasi-periodic oscillations. The nature of the fast, nearly coherent oscillations first detected 16 years ago with RXTE is still unknown. Broad-band spectra give us a clue to the nature of the emission processes in accreting black holes, but it is still not clear what are the main processes producing IR/optical emission and what is the nature of the observed complicated shape of the optical/X-ray cross-correlation. Recently, a number of claims appeared in the literature that the black hole spins can be measured either by continuum fitting model applying the model of the accretion disc spectrum to the spectra of the soft state black holes or from the shape of the iron line. However, the results produced by these two methods are in contradiction. To explain and solve these puzzling differences will necessarily yield major advances in our understanding of the strong gravity regimes.

On the other side of the electromagnetic spectrum, the radio emission is less questionable. It is produced by jets far away from the central object. Recently a strong correlation between the X-ray and radio emission has been discovered arguing in favour of some connection between the accretion process and the jet. The details of this relation and theoretical understanding, however, are still missing. Some of accreting compact objects turned out to be bright gamma-ray emitters as was recently discovered by the Fermi gamma-ray space telescope. The nature of this emission is puzzling, it might be produced in the jet or interacting winds.

The goals of the symposium are to discuss these recent advances in observations and theory of accreting compact objects and to try to shed new light on multiple puzzles.

Program can be found here

Sessions will cover the following aspects: List of invited speakers: Scientific organizing committee (SOC)
Please register at the main site of EWASS-2013.

Working groups

X-ray binaries

Description of the group activity.
Group meetings take place on Wednesdays (first and third of each month), 15.00 in the coffee room.

Stellar explosions

Description of the group activity.
Group meetings take place on Mondays, 15.00 in the coffee room.

AGNs and Very High Energy Astrophysics

Description of the group activity.
Group meetings take place on Wednesday (second and fourth of each month), 15.00 in the coffee room.