Gamma-rays are the most energetic radiation known. How can stars and stellar systems produce these energetic photons?

Normal main-sequence stars do not produce gamma rays. Instead, the gamma rays we see are mostly produced by stellar remnants and supermassive black holes. There are a number of physical mechanisms that produce gamma rays. These include compton upscattering in jets, curvature radiation from pulsars, and nuclear decay.

How do we detect gamma-rays and what can we learn from them?

Gamma rays don’t like to interact with matter, and therefore cannot be focused onto a detector. To detect them, we have to “convince” them to produce an electron-positron pair. Once the gamma ray has converted into particles, we can track them and measure their energies to determine the energy and direction of the original photon.

What will be the impact of the Cherenkov Telescope Array (CTA) in the field of gamma-ray astronomy?

The CTA will provide greater sensitivity and extend significantly lower in energy than the current generation of ground-based gamma-ray observatories, resulting in overlap between ground and space-based gamma ray detectors. This overlapping energy range is often a transition region for the physical processes that create gamma rays. Being able to detect gamma-ray sources over such a large range of frequencies should provide a huge improvement in our understanding of the nature of these sources.

What unique physics can be studied in Gamma Rays binaries? 

There has been a revolution in our understanding of gamma-ray binaries in recent years. The link between low-mass X-ray binaries and the evolution/formation of millisecond pulsars has been clearly demonstrated. The discovery of more and faster millisecond pulsars helps to determine the equation of state for the nuclear material that makes up neutron stars. 

Annia Domènech