Search for very-high-energy gamma ray and neutrino emission from microquasars

Stage numéro : Doctorat-2023-KM-03
Laboratoire :Centre de Physique des Particules de Marseille Case 902
 163 avenue de Luminy - 13288 Marseille Cedex 9
Directeur :Cristinel Diaconu - -
Correspondant :William Gillard - -
Groupe d'accueil :KM3NeT
Chef de groupe :Vincent Bertin - -
Directeur de thèse :Damien Dornic / Jean-Pierre Ernenwein - 04 91 82 76 82 -;

Thématique : Astroparticules

Microquasars are binary objects comprising a compact object (mainly a black hole with a stellar

mass or, in some cases, a neutron star) and a companion star (for example a giant blue star). The

binary system is identified as a microquasar if the presence of relativistic jets is confirmed. Their Xray

emission has been studied in detail over the past two decades to characterize the X-ray emission

cycles that trace the underlying physical phenomena: for example, the phases with material

accretion followed by ejection in jets have typical signatures, in X-rays but also infrared and radio.

The multi-wavelength aspect is thus fundamental for the understanding of these objects. The

relative intensity of each type of radiation as well as their specific characteristics evolve during the

cycle, some phases being potentially the place of very high energy emission.

Currently, the only microquasar possibly detected in very high energy gamma rays is Cygnus X-1,

by MAGIC, in September 2007, associated with strong X-ray activity measured by the RXTE,

Swift and INTEGRAL satellites. For some others sources, only upper limits on the flux of very high

energy gamma rays have been estimated for binaries such as GRS1915+105, Circinus X-1, V4641

Sgr, MAXI J1820+070. HESS and Fermi will continue their operation at least up to 2022, taking

more data to be analysed. The future CTA observatory, operating a hundred Cherenkov telescopes

(99 in Chile and 19 on the island of La Palma), will start to be operational by 2022 and will improve

the sensitivity by an order of magnitude above 100 GeV.

The transient jet phases are also interesting cosmic ray acceleration sites in the galaxy and, therefore

for these sources, high-energy neutrinos may also be emitted. The detection of a neutrino signal is a

smoking gun for the discovery of the sources of the high-energy cosmic rays. KM3NeT is the

second-generation neutrino detector in the Mediterranean Sea. It will be distributed in two sites: a

low energy site ORCA in France (5 GeV-10 TeV) and a high energy site ARCA in Italy (1 TeV-10

PeV). Both detectors will have a sensitivity largely improved compared to ANTARES at low and

high energies. The deployment of the first detection lines has started in both detectors and data are

ready to be analysed. Together with the KM3NeT data, we can combine them with the ANTARES

dataset comprising more than 12 years of continuous data since 2007.

Expected studies to be performed by the candidate:

The Phd student will be a member of the HESS and ANTARES/KM3NeT Collaborations, he will

then contribute to the search for VHE gamma-rays and neutrino emission from microquasars in the

context of multi-wavelength and multi-messenger studies, with the aim of understanding the

mechanisms in play in these systems, in terms of components and efficiency for the acceleration of

high energy particles (especially modeling). The work will essentially consist of data analysis and

their interpretation. The most promising observation phases for the search for very high energy

gamma and neutrino will be performed using X-rays, optical and radio data. It is a key step in

particular for pointing telescopes. In particular, the Phd student will participate to the Target of

Opportunity observations of binary systems by HESS, consisting in observations by HESS of X-ray

binaries, on alerts built from data from other instruments. An estimation of the potential of the

future observatories, CTA and KM3NeT, for the detection of galactic transient sources will be


In the HESS Collaboration, the Phd student will participate to the calibration tasks, in particular

concerning the recently upgraded telescopes, and will take part in the data taking in Namibia. In the

KM3NeT Collaboration, the Phd student will also have to perform service tasks such as the

participation to the calibration, the development of common software, real-time monitoring or

analysis tools...

The candidate should therefore have a good background in astroparticle physics and astrophysics

and interest in the data analysis. The analyses will be performed using C++, Root, and python on

Linux platforms.