SC/0020 - ACCRETION PROCESSES IN ASTROPHYSICS
Academic Year 2022/2023
Free text for the University
ANDREA SANNA (Tit.)
- Teaching style
- Lingua Insegnamento
|[60/68] PHYSICS||[68/30 - Ord. 2020] ASTROFISICA||6||48|
|[60/68] PHYSICS||[68/80 - Ord. 2020] FISICA TEORICA DELLE INTERAZIONI FONDAMENTALI||6||48|
The "Accretion Phenomena in Astrophysics course" is part of the Master's degree in Physics and it aims to provide a general overview of the physical processes that characterize the transfer and accretion of matter into compact objects. A more detailed description of the course is given below.
1. Knowledge and understanding
The course aims to provide the student with the basic tools required to understand the dynamics of fluids and the theory of plasmas applied to mass transfer within an astrophysical binary system. The extreme conditions of the objects involved will also allow the student to acquire knowledge relating to fundamental interactions within the intense magnetic field framework and the state of matter in conditions of strong-field gravity.
2. Ability to apply knowledge and understanding.
During the lectures and exercises, mainly consisting of exercises based on the topics covered in the course and solved in class, students will apply the concepts learned to investigate and to model real complex problems observed in astrophysics.
3. Autonomy of judgment
The student will be stimulated and trained to apply the scientific method as a tool for the analysis of natural phenomena. It will also develop the ability to critically analyze a theory, a model, or an interpretation of natural phenomena. Finally, the student will be asked to independently address the proposed questions as well as to make assessments on the applicable Astronomical methodologies.
4. Communication skills
The student will develop basic knowledge and the ability to present the topics dealt with autonomously and originally through the use of appropriate specific terminology in astrophysics.
During the exam, the student will be required to adequately describe complex physical phenomena, presenting the hypothesized model, the mathematical procedure used, and the results obtained with clarity and precision.
5. Ability to learn
The student will develop the ability to critically learn the course content. In this way, for each topic covered, the student will always be able to understand the approximations on which a physical model is based, its limits in effectively describing the processes that occur in nature, and the critical points on which an experimental verification should be based. The student will be provided with solid methodological support for the study of the topics of the course which can also be used to successfully deal with similar and/or more advanced topics, both in the context of the Master's degree in Physics and within the framework of the Ph.D. program in Physics.
The student must have acquired basic concepts related with Mathematics (differential calculus and integral calculus) and Physics (conservation laws, electromagnetism and basics of statistical mechanics) and adequate preparation on Astronomy and Astrophysics, such as that provided by the Fundamentals of Astronomy and Astrophysics course during the Bachelor degree in Physics.
1.Accretion as a source of energy.
Introduction, accretion efficiency, the Eddington limit, emission spectrum in accretion processes, accretion theory and observation
Introduction, the equations of gas dynamics, steady adiabatic flows, isothermal flows, sound waves, steady spherically symmetric accretion
Introduction, charge neutrality, plasma oscillations and the Debye length, collisions, thermal plasma: relaxation time and mean free path, the stopping power of fast particles by a plasma, transport phenomena: viscosity, the effect of strong magnetic fields, shock waves in plasmas.
4.Accretion in binary systems
Introduction, interacting binary systems, Roche lobe overflow, Roche geometry and binary evolution, disc formation, viscous torques, α-prescription of an accretion disc, accretion in close binaries: other possibilities.
Introduction, radial disc structure, steady thin discs, the local structure of thin discs, the emitted spectrum, the structure of steady α-discs (the standard model), steady discs: confrontation with observations, time dependence and stability, irradiated discs.
6.Accretion on to a compact object
Introduction, boundary layer, accretion on to magnetised neutron stars and white dwarfs, accretion columns, X-ray bursters, black holes.
The course includes 48 hours of frontal teaching, divided into 24 lessons of 2 hours. The teaching will take place using the blackboard and the video projector.
The teaching will be delivered mainly in presence, integrated with online strategies, in order to guarantee its use in an innovative and inclusive way.
Furthermore, the exercises can be carried out through forms of remote interaction with the available IT supports.
Verification of learning
The exams will consist of an oral interview on the topics covered during the course. The level of acquired knowledge of the program carried out, the ability to make connections between concepts and knowledge, the ownership of language and the ability to exhibit will be assessed and evaluated.
If required by the epidemiological situation, the oral interview could be carried out remotely using videocall platforms (Teams, Zoom, etc).
1) Frank, King, & Raine, Accretion Power in Astrophysics, Third Edition, Cambridge University Press, 2005
2)Kolb, Extreme environment astrophysics, Cambridge University Press, 2010
Students attending the course will have access to supplementary material, lesson slides, texts, notices and calendars on the teacher's website.