## The Final exam will be held on Friday, April 29, 2022, at 9.15-12.15 in L9.

## Questions for the exam: [PDF]

## 765649S

# Astrophysics

an advanced course (10 credits)

at the Space Physics and Astronomy research unit, University of Oulu

#### The course period: January 10 – April 29, 2022

#### Lectures take place usually on Monday and Wednesday at 14-16, exercise and practical sessions on Friday at 10-12, see Peppi for detail. However, classes on Friday will only occur when I announce them!

#### The course is lectured in English

#### Teacher: Vitaly Neustroev, MA 308, vitaly[-at-]neustroev.net

Course plan:

- Stellar structure and evolution
- Radiative processes
- Stellar photospheres
- Interstellar Medium
- etc…

Theoretical and practical considerations will be supplemented with the home exercises which constitute the important part of the course.

Literature:

Textbook choice for this course is largely a matter of personal taste. I provide below a list of recommended books. Study them in parallel with the lectures.

- Stellar Structure and Evolution – Onno Pols, Utrecht, 2014 (Free)
- An Introduction to the Theory of Stellar Structure and Evolution – Dina Prialnik
- Introduction to Stellar Astrophysics: Vol 2 – E. Böhm-Vitense
- Observations and analysis of stellar photospheres – D. F. Gray
- Lecture notes (not enough!)

A List of Errors for the Third Edition of the book by D. F. Gray

Compulsory problems (return by the deadline). 5+ sets (30% of the final score).

- deadline 09.02.2022 [set 1] * Solutions
- deadline 01.03.2022 [set 2] * Solutions
- deadline 28.03.2022 [set 3] * Solutions
- deadline 30.03.2022 [set 4] * Solutions
- deadline 20.04.2022 [set 5] * Solutions

Schedule

**Lecture 1: January 10:**Introduction (What is Astrophysics and Theoretical Astrophysics? Astronomical units)

PDF**Lecture 2: January 12:**Stars (Role of stars; Definition; What can we learn from observations? Properties of stars; Stellar timeline)

PDF**January 14:**NO CLASS**Lecture 3: January 17:**Stars (basic assumptions, mass conservation, hydrostatic equilibrium, virial theorem)

PDF**Lecture 4: January 19:**Stars (Timescales of stellar evolution. Conditions in stellar interiors)

PDF (Updated on 24.01.2022)**January 21:**NO CLASS**Lecture 5: January 24:**Stars (Energy generation. The equation of conservation of energy)

PDF**Lecture 6: January 26:**Basics about radiative transfer (Radiation terms, specific intensity, interaction radiation – matter, parallel-ray radiative transfer equation)

PDF (Updated on 31.01.2022)**January 28:**NO CLASS**Lecture 7: January 31:**Basics about radiative transfer (solution of the parallel-ray RTE, Mean Intensity, Flux, and K-integral, stellar magnitudes)

PDF**Lecture 8: February 2:**Basics about radiative transfer (RTE in plane-parallel atmosphere. The equations of stellar structure and possible ways to solve them. Boundary conditions. Convection and conditions for its occurrence.)

PDF

**Compulsory problems:**[Set 1] (return by February 9).**February 4:**NO CLASS**Lecture 9: February 7:**The equations of stellar structure (equation of state – EOS, stellar opacity)

PDF**Lecture 10: February 9:**Nuclear Energy Production (Basics on nuclear reactions, the binding energy, Quantum tunnelling, Reaction cross-section, the Gamow peak, Nuclear Reaction Rates, Electron shielding)

PDF (Updated on 14.02.2022)**February 11:**NO CLASS**Lecture 11: February 14:**Nuclear reactions in stellar interiors (Energy generation, PP-chains & CNO-cycle, Helium burning, Carbon burning and beyond, iron and heavier elements, Composition changes)

PDF**Lecture 12: February 16:**Solution of the Equations of Stellar Structure (The stellar structure equations and how to solve them? Simple stellar models. Polytropic models. Lane-emden equation. Different relationships for polytropic stars. Chandrasekhar mass. Dynamical stability of stars)

PDF (Updated on 21.02.2022)**February 18:**NO CLASS**Lecture 13: February 21:**Schematic stellar evolution

PDF

**Compulsory problems:**[Set 2] (return by March 1).**Lecture 14: February 23:**Star formation

PDF**February 25:**NO CLASS**Lecture 15: February 28:**Identification of Young Stars. Pre-main sequence star evolution (the Hayashi track and the Henyey track). Main Sequence stars.

PDF (Updated on 2.03.2022)**Lecture 16: March 2:**Main Sequence stars (cont). Evolution of low-mass and high-mass stars. The initial mass function.

PDF (Updated on 19.04.2022)**March 4:**Mid-term exam**Lecture 17: March 14:**What is a stellar atmosphere? Why should we care about it? What can we learn from observations?

PDF**Lecture 18: March 16:**Radiative transfer (Radiative transfer equation in plane-parallel atmosphere. Limb darkening), Solution to transfer equation, Eddington-Barbier relation. Grey atmosphere. Radiative equilibrium. The depth dependence of the source function. Eddington approximation. Temperature structure of the grey atmosphere.

PDF**Lecture 19: March 21:**LTE (Maxwellian distribution in velocities, Boltzmann equation, Saha formula).

PDF**Lecture 20: March 23:**Stellar Opacity (Bound-bound, bound-free and free-free absorptions). Negative hydrogen ion H^{–}as the sources of opacity.

PDF (Updated on 28.03.2022)**Lecture 21: March 28:**Other sources of opacity (He and Metallic absorptions, Scattering, Effect of nongreyness of the temperature structure, Balmer jump).

PDF**Lecture 22: March 30:**Spectral lines (Equivalent Width, FWHM, FWZI, Radial Velocity). Spectral line formation (Einstein coefficients. Natural Line Width, Natural broadening, Doppler broadening).

PDF * Homework: slide 22**Lecture 23: April 4:**Spectral line formation (Natural broadening, Doppler broadening, Pressure broadening, Convolution of different broadening processes, Ingis-Teller relation, Rotational and Instrumental broadening).

PDF**Lecture 24: April 6:**Simple line transfer, Schuster-Schwarzschild model, Theory of line formation, Curve of Growth. Scattering in lines, Transfer Equation including lines, The Milne-Eddington model, Residual flux of the line, Absorption and scattering lines, Schuster Mechanism for Line Emission.

PDF**Lecture 25: April 11:**Non-LTE (Statistical equilibrium, Two-level approximation, the line source function, LTE versus non-LTE). Spectral type sequence. Towards the Model Photosphere (Hydrostatic equilibrium, Gas Pressure, Electron Pressure).

PDF**Lecture 26: April 13:**Radiation Pressure. Eddington limit. Measuring temperatures and surface gravities (Direct measurement of radii. Determining teff and surface gravity, Model-independent methods, Model-dependent methods, Atmospheric models, Photometric methods, Spectroscopic methods).

PDF * Spectral classification**Lecture 27: April 20:**A short introduction to the Interstellar Medium.

PDF**Lecture 28: April 22:**ISM: Ionized regions. Strömgren Spheres.

PDF

** Compulsory problems:** [Set 3] (return by March 28).

** Compulsory problems:** [Set 4] (return by March 30).

** Compulsory problems:** [Set 5] (return by April 20).