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

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 will cover most of the relevant material

Main textbooks:

Asteroseismology, Aerts, Kurtz, and Christensen-Dalsgaard, Springer

Asteroseismic data analysis - foundations and techniques,  Basu & Chaplin, 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.

 

Assessment methods

The exam (oral) is based on two parts:

1- presentation by the student of a small project of their choice (typically on the data analysis and / or modelling of a specific star or class of pulsating stars)

2- questions to assess the overall level of understanding and the ability of the student to link the different topics of the course.

Teaching tools

Slides, blackboard, and - when relevant - python notebooks with examples on how to run and interpret results from stellar models / data analysis techniques.

Links to further information

https://www.asterochronometry.eu

Office hours

See the website of Andrea Miglio