2023-2024 / SPAT0007-2

Variable stars


20h Th, 10h Pr

Number of credits

 Master in space sciences (120 ECTS)3 crédits 


Grégor Rauw

Language(s) of instruction

English language

Organisation and examination

Teaching in the first semester, review in January


Schedule online

Units courses prerequisite and corequisite

Prerequisite or corequisite units are presented within each program

Learning unit contents

In astrophysics you are only allowed to watch your targets, you cannot manipulate them in a lab. Therefore, it is important to gather as much information as possible to understand the nature of the objects that are being investigated. In this context, temporal variability provides a precious tool.
In this course, the observational properties of many different categories of variable stars (including single and multiple objects) are presented. Various techniques to study these objects are described and the latest models derived from these observations are presented.
For single stars, the lectures focus on the different categories of pulsating stars across the Hertzsprung-Russell diagram as well as their period-luminosity relations. The variability of massive stars, mainly due to structures in their stellar winds, is also described. We further address some categories of late-type stars that display variability: R Corona Borealis stars, pre-main sequence stars and active, flaring objects. The second part of the course deals with multiple systems harbouring two or more stars. We consider the techniques used to infer fundamental stellar parameters (masses, radii,...) from the study of spectroscopic and eclipsing binaries. We also discuss interacting binaries, such as cataclysmic variables, novae, X-ray binaries,...
This course partially builds upon the flipped classroom model. Regularly, the students are given a "challenge". They should reflect on it and present their solution at the next course.

Learning outcomes of the learning unit

After completing this course, the students will be able to answer notably three major questions:

  • What are the general properties of variable stars and how can they be used to better understand the processes in the Universe?
  • How to extract the most relevant information from spectroscopic time-series and/or from photometric light curves?
  • How to interpret the observed variability?

Prerequisite knowledge and skills

Good knowledge of mathematics, physics and classical mechanics.

Planned learning activities and teaching methods

Most of the lectures will take place face-to-face (if the sanitary conditions allow so), but some will be delivered as podcasts. The course adopts a partial flipped classroom model: questions will be regularly asked to the students and they should use the tools made available to them to answer those questions for the next lecture.
During a hand-on session, the students have the opportunity to analyze the lightcurve of an eclipsing binary system using dedicated software.
Based on the concepts taught in this course, the students will complete a personal project consisting in a critical analysis of a scientific article on a variable star and the preparation of a proposal for an observing program of a variable star with the TIGRE robotic telescope.

Mode of delivery (face to face, distance learning, hybrid learning)

Blended learning

Additional information:

The face-to-face lectures (if the sanitary conditions are favorable) are usually scheduled as 3h/week during the first semester.

Some lectures could be provided as podcasts.

Recommended or required readings

The lecture notes are provided in English as a pdf file.

All these documents are made available exclusively to the students of this course for a strictly personal and private use, and shall not be shared with a third party. Furthermore, it is forbidden to submit these documents to an artificial intelligence or to an artificial intelligence-powered language model. This restriction equally holds if the goal of such a submission would be to generate a summary for personal use.


Exam(s) in session

Any session

- In-person

oral exam

Written work / report

Continuous assessment

Additional information:

The evaluation is composed of two parts: 25% based upon the participation to the recurrent challenges and the remaining 75% based upon the assessment of the personal report and its oral defense.

Any use of an artificial intelligence or an artificial intelligence-powered language model in the preparation of the personal report and/or the answers to the challenges is strictly forbidden and will be sanctioned as a fraud. 

Work placement(s)

Organisational remarks and main changes to the course



Prof. Gregor Rauw Institut d'Astrophysique et Géophysique, Bât. B5c Allée du 6 Août, 19c 4000 Liège
Tel. +32-(0)4 366 9740 e-mail: g.rauw@uliege.be

Association of one or more MOOCs