Duration
20h Th, 10h Pr
Number of credits
| Master in space sciences (120 ECTS) | 3 crédits |
Lecturer
Language(s) of instruction
English language
Organisation and examination
Teaching in the second semester
Schedule
Units courses prerequisite and corequisite
Prerequisite or corequisite units are presented within each program
Learning unit contents
Stellar spectra are formed in the stellar atmospheres and they contain a wealth of information on the physical conditions in these atmospheres. The goal of this course is to establish the link between the physical parameters on the one hand and the observable quantities (i.e. the spectra) on the other hand.
The course starts by reviewing the link between the Hertzsprung-Russell diagram and the stellar spectra. Next, we introduce the main classification criteria that are used to assign a spectral type directly from the observations. We then recall the fundamental notions of the interaction between matter and radiation and we introduce the concept of radiative transfer both in static and moving atmospheres. Stellar atmosphere codes aiming at the calculation of synthetic spectra rely on a number of assumptions (hydrostatic equilibrium, local thermodynamical equilibrium or absence of the latter) and we discuss these different hypotheses. We then review the various effects that determine the aspect of spectral lines (intrinsic width, Doppler and pressure broadening, rotational velocity, chemical composition). The modeling of expanding atmospheres (stellar winds) is also addressed. Finally, we consider the issue of stellar magnetic fields and their impact on the light and its polarization.
Learning outcomes of the learning unit
The purpose of this course is to explain the link between physical parameters of the stars and the characteristics of their spectra. Upon completion of this course the students will be able to understand how stellar properties such as the temperature, the luminosity, the chemical composition,... can be inferred from the analysis of stellar spectra.
Prerequisite knowledge and skills
Good knowledge of physics (atomic spectroscopy) and mathematics.
Planned learning activities and teaching methods
Several tutorial sessions are organized to illustrate the concepts introduced during the lectures.
Mode of delivery (face-to-face ; distance-learning)
About 22 hours of theoretical lectures + 8 hours of tutorial sessions. The course takes place during the second semester.
Recommended or required readings
The lecture notes are provided in English through a pdf file available on the eCampus website of the course.
Assessment methods and criteria
The evaluation emphasizes the understanding of the course and the ability to use the techniques that have been taught. To successfully pass the exam students have to learn and understand the course. The assessment is based on a written exam consisting of theory questions and exercises.
Work placement(s)
Organizational remarks
N/A
Contacts
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
Adaptation of teaching commitments following the COVID-19 pandemic for the May-June 2020 session
Teaching methods implemented : distance-learning
During the confinement due to the Covid-19 pandemic, lectures are given remotely via skype. Furthermore, podcasts recorded with Camtasia are provided on eCampus. Finally, the details of the exercises and other mathematical developments that would normally be presented on the blackboard are provided as a pdf file on eCampus.
Assessment subjects
A new list of theory questions adapted to an on-line exam has been communicated to the students on 10 April. The exercise will be taken from chapters 3 or 4 (no exercise from chapter 5). The exam will also include a spectral classification as previously announced.
Assessment methods
The exam will be done remotely via skype and includes (1) a theory question to be answered orally (taken from the list that was provided on 10 April), (2) an exercise (resolution on a sheet of paper and photograph of the resolution to be sent by e-mail), and (3) a spectrum to be classified (argumentation to be sent by e-mail). The exam will thus be fully open book, and the students are invited to use the slides of the course as support for answering the theory question.
Contacts
E-mail address: g.rauw@uliege.be
Adaptation of teaching commitments following the COVID-19 pandemic for the Aug-Sept 2020 session
Assessment subjects
Same as for the May-June 2020 session.
Assessment methods
Same procedure as for the May-June 2020 session.
Contacts
Same address as for the May-June 2020 session.