Course
2024-2025

Knowledge of calculus, special relativity and electromagnetism at the bachelor’s level is required. In terms of the Leiden curriculum, the prerequisites for this course are Analyse 2 or Analyse 2 NA, Introductie Moderne Natuurkunde, Classical Electrodynamics Inleiding Astrofysica

## Description

The main goal of this course is to understand and recognize the different ways matter and light interact in an astrophysical context, including emission, scattering and absorption. This allows us to physically interpret the light that we observe from astrophysical sources. Throughout the course, we will rely on mathematical derivations to gain a deep understanding of the processes involved.

We will define a number of fundamental concepts necessary to unambiguously discuss radiation. This is followed by the introduction of the basic equation of radiative transfer, which describes how radiation changes as it traverses a medium. In the remainder of the course we will keep coming back to this equation. This part will be concluded with a discussion of a few methods to solve the equation of radiative transfer.

Then we take a step back and examine the relation between the concepts introduced earlier. We will find that radiation can only be generated and changed by accelerating electrical charges, and we will deduce several fundamental relations. We will also investigate how the emission of radiation is changed when the emitting particle is moving relativistically (beaming).

This is followed by a discussion of three important mechanisms to produce continuous radiation, i.e., radiation that changes only weakly with wavelength. All these processes involve freely moving electrons: in an ionized plasma (Bremsstrahlung or free-free emission); in the presence of magnetic fields (cyclotron and synchrotron emission, depending on whether the electrons move non-relativistically or relativistically); and the interaction between relativistic electrons and photons (inverse Compton scattering).

We will conclude the lecture series with the production of radiation at discrete wavelengths, i.e. spectral lines. These processes involve electrons bound to atoms or molecules.

## Course objectives

The main objective of this course is to be able to physically interpret a spectrum from an astrophysical source, based primarily on its continuum emission and to a lesser extent on its spectral lines.

Upon completion of this course you will be able to:

• Describe the physical processes through which radiation is emitted, changed or absorbed

• Solve the equation of radiative transfer for a range of physical conditions

• Construct a spectrum for a range of astrophysical sources including isothermal ionized clouds, stars and charged particles moving in magnetic fields

• Physically interpret continuum spectra including free-free emission, synchrotron emission, inverse Compton radiation and Comptonized blackbody radiation, deducing source properties such as temperature, density and optical depth

• Physically interpret spectral lines from single charged particles, simple atoms and diatomic molecules.

## Timetable

Schedule

In MyTimetable, you can find all course and programme schedules, allowing you to create your personal timetable. Activities for which you have enrolled via MyStudyMap will automatically appear in your timetable.

Questions? Watch the video, read the instructions, or contact the ISSC helpdesk.

Note: Joint Degree students from Leiden/Delft need to combine information from both the Leiden and Delft MyTimetables to see a complete schedule. This video explains how to do it.

## Mode of instruction

• Lectures

• Exercise classes

## Assessment method

• Written exam

• Homework assignments (bonus points)

• Radiative Processes in Astrophysics, Rybicki & Lightman, ISBN 9780471827597 (required). The electronic version of this book is also available in the University library.

## Registration

As a student, you are responsible for enrolling on time through MyStudyMap.

In this short video, you can see step-by-step how to enrol for courses in MyStudyMap.
Extensive information about the operation of MyStudyMap can be found here.

There are two enrolment periods per year:

• Enrolment for the fall opens in July

• Enrolment for the spring opens in December

Note:

• It is mandatory to enrol for all activities of a course that you are going to follow.

• Your enrolment is only complete when you submit your course planning in the ‘Ready for enrolment’ tab by clicking ‘Send’.

• Not being enrolled for an exam/resit means that you are not allowed to participate in the exam/resit.

## Contact

Lecturer: Prof. Dr. M (Michiel) Hogerheijde

## Remarks

Software
Starting from the 2024/2025 academic year, the Faculty of Science will use the software distribution platform Academic Software. Through this platform, you can access the software needed for specific courses in your studies. For some software, your laptop must meet certain system requirements, which will be specified with the software. It is important to install the software before the start of the course. More information about the laptop requirements can be found on the student website.