Particle and Astroparticle Physics Seminar

Binary systems observed with H.E.S.S. telescopes

Chistian Mariaud

École Polytechnique

Binary systems in gamma astronomy are stellar objects involving a supermassive star with a compact object (neutron star or black hole), the lightest in orbit around the other. They regularly emit at high energy and very high energy (E > 100 GeV) for detection by Imaging Atmospheric Cerenkov Telescopes (VERITAS, MAGIC and H.E.S.S.). High Energy stereoscopic System (H.E.S.S.) is located in Namibia. The acronym was chosen in honor of Victor Hess. He was the first to observe cosmic rays. H.E.S.S. has five telescopes, four with a mirror just under 12 m in diameter. In 2012, a fifth telescope began observation in the centre of the square formed by the other four. This telescope, much larger in size (28 m diameter) is able to get events at lower energy and make the connection with Fermi-LAT experiment. The latest preliminary results of these two binary systems will be presented during this seminar.

Currently, seven binary systems are known, they are located in our Galaxy or in its environment. The latest was discovered in Magellan Cloud (LMCP3). Despite their low relative number, they present a great diversity of behavior. However they are all characterized by a modulation of gamma photon flux which depends on the position of the lightest object. During this presentation, we will focus on two binary systems:

- LS 5039: O6.5V star with unknown compact object,
- PSR B1259: Be-star and its circumstellar disk with a pulsar.

H.E.S.S. telescopes have regularly observed these objects for more than 10 years and have now collected substantial data. One improvement of the data will be also exposed: the atmosphere can be degraded during LS5039 observations. It is therefore important to know the transparency coefficient of the atmosphere.

To conclude this seminar, Masterclass took place for the first time within the H.E.S.S. collaboration. Students were able to have access to real data and perform analysis as researchers.