96389 - Advanced Stellar Physics and Asteroseismology

Learning outcomes

This course presents students with the theoretical underpinnings of asteroseismology, i.e. the study of stellar properties based on observations of stellar oscillations. By the end of the module students will be able to explain the nature of normal oscillation modes, and relate them to the characteristics of the internal structure of stars. Students will also appreciate the wider implications of asteroseismology on high-precision stellar physics, on studies of stellar populations, and on the characterisation of exoplanetary systems.

Course contents

Useful prerequisites: Students are expected to be familiar with the basic equations of stellar structure and evolution, and with elementary concepts of waves, Fourier analysis, and programming in Python. Essential background material will be recalled when needed.

The topics to be covered are:

 

1.  Overview of asteroseismology

• basic principles and scope of asteroseismology, observational techniques
• stellar oscillations across the HR diagram

 

2. Theoretical underpinnings

• brief recall of the equations describing stellar structure
• method of small perturbations and equations of non-radial adiabatic stellar oscillations
  
• propagation diagrams and nature of normal modes in stars: acoustic, gravity and mixed modes
• asymptotic approximation of pressure and gravity modes
• analytical description of mixed modes
• variational principle of non-radial adiabatic stellar oscillations, analogies with simple physical systems
• effect of rotation on the oscillation frequencies
• mode excitation and damping
• case study: evolution of the surface properties, internal structure, and seismic properties of a 1-solar-mass star, from the main sequence to the white-dwarf stage

 

3. Analysis of asteroseismic data

• elements of time-series analysis
• heat-driven versus stochastically excited modes
• global properties of the oscillation spectrum
• measuring individual-mode frequencies

 

4. Asteroseismic inference:

• forward modelling and inversion techniques
• inferring stellar properties
• inferring internal rotational profile
• examples of asteroseismic inference from various classes of pulsating stars:

1. test of stellar physics (transport of chemical elements and angular momentum, convective boundary mixing, microphysics)
2. synergies with the searches for and characterisation of exoplanets,
3. distance scale
4. stellar populations and the evolution of the Milky Way (with emphasis on inferring precise and accurate ages of stars)

Readings/Bibliography

The slides presented by the lecturer, together with notes and material made available on Virtuale, will cover most of the material required for the exam.

Required material

Lecture slides, notes, selected papers and Python notebooks made available on Virtuale.

Recommended textbooks

Aerts, Christensen-Dalsgaard & Kurtz, Asteroseismology, Springer.

Basu & Chaplin, Asteroseismic Data Analysis: Foundations and Techniques, Princeton Series in Modern Observational Astronomy.

Additional reading

Lecture Notes on Stellar Oscillations, Christensen-Dalsgaard

 

Teaching methods

Lectures, using a combination of slides and derivations on the board

When relevant, the lecturer will also suggest recent publications / reviews that will be discussed together with the students during the lectures.

The module will also include student-centred learning activities in which students will learn how to run (and interpret the results of) codes to compute stellar models, their oscillation frequencies, and to analyse data collected from the Kepler and TESS missions.

Teaching material, including slides, selected notes, papers and, when relevant, Python notebooks, will be made available through Virtuale.

 

Assessment methods

The final exam is oral and consists of two parts:

1. A presentation by the student of a small project of their choice, typically focusing on the data analysis and/or modelling of a specific star or class of pulsating stars. The topic of the project must be agreed with the lecturer in advance. The presentation should demonstrate the student’s ability to apply concepts and methods discussed during the course to a specific scientific case.

2. Questions aimed at evaluating the overall level of understanding of the course contents, and the student’s ability to connect and critically reflect on the various topics covered in the course.

 

The project presentation and the discussion of the course topics both contribute to the final mark. The project is mainly used to assess the ability to apply methods and interpret results critically; the oral questions are mainly used to assess the understanding of the theoretical foundations, the physical interpretation of stellar oscillations, and the ability to connect asteroseismic diagnostics to stellar structure and evolution.

The overall assessment (expressed as a mark out of thirty) will be graded as follows:

• 18–19: Knowledge limited to a very small number of topics covered in the course; analytical skills emerge only with the lecturer’s guidance; generally correct use of language.

• 20–24: Knowledge of a limited number of topics; autonomous analytical skills evident mainly in routine or procedural matters; correct use of language.

• 25–28: Broad knowledge of the topics; ability to conduct independent critical analysis; confident use of subject-specific terminology.

• 29–30L: Comprehensive knowledge of the course content; demonstrated ability to critically and independently analyse and connect concepts; full command of subject-specific terminology; strong argumentative and self-reflective skills.

As established by the Degree Programme Board, a grade may be declined no more than twice.

Students with learning disabilities or temporary or permanent disabilities are invited to contact the relevant University office as early as possible: https://site.unibo.it/studenti-con-disabilita-e-dsa/it . The office will provide guidance on any necessary adjustments, which must be submitted to the course instructor at least 15 days in advance. The instructor will evaluate their compatibility with the course’s academic objectives.

Regarding assessment, the use of generative Artificial Intelligence is not allowed unless explicitly authorised by the lecturer for specific parts of the project. Any use of generative AI must be declared by the student and must not replace the student’s own analysis, interpretation and critical discussion. Undeclared or unauthorised use of generative AI in the assessment constitutes a breach of academic integrity.

Teaching tools

Slides, blackboard, selected scientific papers and, when relevant, Python notebooks with examples on how to run and interpret results from stellar models and asteroseismic data-analysis techniques.

Teaching material will be made available through Virtuale.

Links to further information

https://www.asterochronometry.eu

Office hours

See the website of Andrea Miglio