HIGH ENERGY ASTROPHYSICS
Academic year and teacher
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- Versione italiana
- Academic year
- 2019/2020
- Teacher
- CRISTIANO GUIDORZI
- Credits
- 6
- Didactic period
- Secondo Semestre
- SSD
- FIS/05
Training objectives
- The objectives of the course are supplying solid knowledge and mastering of the treated topics. The acquired knowledge will enable the student to delve deeper into the main arguments of cutting-edge research in the field of high-energy astrophysics.
This course addresses the main radiative processes in astrophysics and their relevance in the field of high energy astrophysics. Special attention is paid to some of the most powerful transient astrophysical objects that play a crucial role in the evolution of the Universe, such as supernovae explosions, gamma-ray bursts, fast radio bursts. These explosive phenomena are the subject of cutting-edge research. The course presents the basic physics underlying these objects with particular emphasis on the recent discoveries (such as the recently discovered new class of so-called superluminous supernovae) and their interpretations. To this aim, the course presents elements of the astrophysical fluid dynamics, the jump conditions for both relativistic and non-relativistic shocks. Then it moves to study of the electromagnetic waves through astrophysical plasmas with emphasis on the implications for newly discovered fast radio bursts. Finally, the course discusses particle acceleration in astrophysics through the so-called Fermi first- and second-order mechanisms.
The student will be supplied with the formal rigour and will show their abilities in properly formulating and addressing problems concerning the treated subjects, required to undertake any research activity in the related fields. Prerequisites
- The course requires familiarity with the basics of special relativity, classical electromagnetism, general physics, classical and quantum mechanics as well as statistical physics. Elements of theory of stellar evolution and of binary stars are just advisable.
Course programme
- Main topics: Radiative transfer (8 hours). Radiative processes (12 hours). Fluid dynamics and shocks (8 hours). Supernovae and Gamma-ray bursts (10 hours). Electromagnetic waves through plasmas and fast-radio bursts (8 hours). Fermi acceleration mechanisms (2 hours).
Detailed topics: elements of special relativity in astrophysics. Radiative transfer. Radiation from moving charged particles, Larmor formula, dipole approximation. Polarisation of radiation. Radiative processes: Thomson scattering, bremsstrahlung, synchrotron radiation, Compton and inverse Compton scattering, along with several astrophysical examples. Basic equations of fluid dynamics in astrophysics. Jump conditions for both relativistic (Taub) and non-relativistic (Rankine-Hugoniot) shocks. Self-similar solutions (Sedov-Taylor, Blandford-McKee). Stellar explosions. Supernovae: classification and interpretations. Gamma-ray bursts: classification and interpretations. Electromagnetic waves through astrophysical plasmas. Dispersion measure and Faraday rotation. The novel phenomenon of fast radio bursts, along with some possible proposed interpretations. Fermi first and second order mechanisms in the context of cosmic ray acceleration. Didactic methods
- The lectures are delivered through slides that the teacher makes available on the web soon after they have been presented and discussed. During classes the teacher very often intersperses slides with calculations of the relevant quantities, which are estimated by means of specific examples and exercises. This way, the student becomes very familiar with the kind of exam and the sort of questions he/she will be expected to address in the oral exam, as well as with the evaluation criteria adopted by the teacher.
Learning assessment procedures
- During classes the teacher occasionally assigns exercises along with the numerical values of the solutions to motivate the students to practice and test the knowledge they are expected to acquire on the topics presented by the teacher. A detailed step-by-step solution is available on request to the students in the following weeks. The final exam consists of a unique oral session with a typical duration of 45 to 60 minutes, during which the student is asked both general questions about theory and more specific problems. These, in particular, will test the student's capability of properly addressing the problems. To this aim, the student will have to know the values of the fundamental constants and how to use them to estimate the requested astrophysical quantities.
The exam aims at assessing the expertise acquired by the student, their ability to establish connections between the different topics and aspects of the course, as well as the formal mathematical rigour demanded by each topic. Reference texts
- Slides are made available. The first four textbooks listed below are the main source of reference for the course. The remaining textbooks are additional sources for a more in-depth study.
1) H. Bradt, "Astrophysics Processes", Cambridge
2) G.B. Rybicki, A.P. Lightman, "Radiative Processes in Astrophysics", Wiley
3) M. Vietri, "Astrofisica delle Alte Energie", Bollati Boringhieri.
4) M. Longair, "High Energy Astrophysics", Cambridge University Press.
5) K. Thorne, R. Blandford, "Modern Classical Physics", Princeton
6) J.E. Truemper, G. Hasinger, "The Universe in X-Rays", Springer
7) C.T. Russell, J.G. Luhmann, R.J. Strangeway, "Space Physics. An Introduction", Cambridge University Press (2017).
8) C. Grupen, "Astroparticle Physics", Springer
9) Burke, B.F., Graham-Smith, F.: An Introduction to Radio Astronomy. Third Edition. Cambridge University Press (2010).
10) Marr, J.M., Snell, R.L., Kurtz, S.E.: Fundamentals of Radio Astronomy. Observational Methods. CRC Press, Taylor & Francis Group (2015).
11) B. Ryden, "Introduction to Cosmology", 2nd Edition, Cambridge University Press (2017).
