96393 - High Energy Astrophysics

Course Unit Page


This teaching activity contributes to the achievement of the Sustainable Development Goals of the UN 2030 Agenda.

Quality education

Academic Year 2022/2023

Learning outcomes

This course focuses on the description of mechanisms and physical processes responsible for the emission observed from populations of Galactic and extra-galactic sources in the high-energy portion of the electromagnetic spectrum (mostly X-ray and Gamma-ray). All the phenomena will be illustrated using results from state-of-the-art X-ray and Gamma ray observatories. Students will be able to critically comprehend and discuss the high-energy emission properties of different classes of cosmic sources (e.g. compact X-ray sources such as X-ray binaries and Active Galactic Nuclei, clusters of galaxies, exploding stars such as Supernovae and Gamma Ray Burst, the Galactic Center). Through a multi-wavelength (and multi-messenger) approach, students will be able relate the X-ray properties of the observed sources with their emission at other wavelengths (and other messengers). The student is expected also to attain a basic knowledge of the techniques related to the detection of X-ray and Gamma-ray photons and on the properties of past, present, and future X-ray telescopes.

Course contents


  • Recap on emission mechanisms: blackbody/bremsstrahlung/synchrotron/Compton scattering and Inverse Compton scattering, and some examples in the field of high-energy Astrophysics. Line production. Plasma physics (collisional and ionization equilibrium)
  • History of the high-energy Astronomy. Excursus on the properties of the main X-ray/Gamma-ray satellites of the 'golden age'.
  • Detection techniques for high-energy photons. X-ray and Gamma-ray detectors; CCDs in X-rays. Wolter-type telescopes and coded-aperture masks. Cerenkov radiation.


  • Theory, Eddington limit, accretion discs. Accretion and ejection processes (jets, winds)
  • Physics of compact objects: white dwarfs, Chandrasekhar limit, neutron stars, pulsars, black holes (with some mentions on relativistic astrophysics)


  • X-ray binaries: phenomenology, classification and physical properties. Cataclysmic variables,Low- and High-mass X-ray binaries, candidates black holes.
  • The Galactic Center: a multi-wavelength perspective. Emission from point-like and extended X-ray/Gamma-ray sources. Properties of the Fermi bubbles and other extended features. Matter infalling onto SgrA*.
  • X-ray emission from Solar System objects.
  • Stellar X-ray Astronomy: main-sequence (MS) and pre-MS stars/very low-mass stars.
  • Ultraluminous X-ray sources


  • Clusters of galaxies and cooling flows
  • Active Galactic Nuclei (AGN): X-ray spectral components in X-rays: models vs. observations.
  • X-ray surveys in the last decade. AGN contribution to the cosmic X-ray background. Open issues.

  • Gamma ray bursts: phenomenologies, origin and emission mechanisms.
  • High Energy sources of Gravitational waves and multi-messenger astrophysics



  • Malcolm S. Longair: "High-Energy Astrophysics", Cambridge University Press


  • George B. Rybicky, Alan P. Lightman: "Radiative Processes in Astrophysics", Wiley
  • J. Frank, A. King & D. Raine: "Accretion Power in Astrophysics", Cambridge University Press

For each lecture, few (at most) selected resources (papers, slides of seminars, web-pages) will be given to complement the material on the Longair's book.

The slides used during the lectures will be also made available, at the end of the lecture.

Teaching methods

Lectures with the aid of slides and blackboard. From time to time, during the lecture we will critically analyze recent publications and/or reviews on the lecture topics. Time will also be devoted to "questions and answer" sessions at the end of the macro-topics.

During the course few lectures will be devoted to specialistic seminars (2 hours each) given by colleagues of INAF-OAS and CTA, on future perspectives on high-energy astrophysics studies and synergies with theory/modelling.

Assessment methods

Oral exam where the candidate should demonstrate to have an organic view of the discipline. The exam will start with a topic chosen by the student. The candidate should be able to deduce relations among physical quantities related to high-energy astrophysics in a non mnemonic way.

Teaching tools

Blackboard and presentations of powerpoint slides.

Office hours

See the website of Marcella Brusa