## The Final exam will be held on Friday, December 20, 2019, at 13.15-17.00 in L9.

## Questions for the exam: [PDF]

## 765629S

# Stellar Atmospheres

an advanced course (10 credits)

at the Astronomy research unit, University of Oulu

#### The course period: September 4 – December 20, 2019

#### Lectures, exercise and practical sessions take place usually on Wednesday at 14-16 and Friday at 12-14, see WebOODI for detail.

#### The course is lectured in English

#### Teacher: Vitaly Neustroev, MA 302, vitaly[-at-]neustroev.net

Course plan:

- Radiation terms and definitions
- Stellar photospheres
- Stellar atmospheres
- etc…

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

Literature:

- Introduction to Stellar Astrophysics: Vol 2 – E. Böhm-Vitense
- Observations and analysis of stellar photospheres – D. F. Gray
- Lecture notes (not enough!)

Known typos and errors in the book by D. F. Gray

Schedule

**Lecture 1: September 4:**Introduction (What is a stellar atmosphere? Spectral Types, Luminosity Classes, Magnitudes, Bolometric Flux and Bolometric Correction)

PDF**Lecture 2: September 6:**Basics about radiative transfer (Radiation terms, Specific and mean intensity, Flux & luminosity, Black body radiation (Planck function), Effective temperature (Stefan-Boltzmann law), Brightness and Color temperatures)

PDF**Lecture 3: September 11:**Basics about radiative transfer (radiation density and pressure), Interaction radiation – matter, Parallel-Ray transfer equation.

PDF**Lecture 4: September 13:**Radiative transfer (Radiative transfer equation in plane-parallel atmosphere. Limb darkening), Solution to transfer equation, Eddington-Barbier relation. Grey atmosphere.

PDF**Lecture 5: September 18:**Grey atmosphere. Radiative equilibrium. The depth dependence of the source function. Eddington approximation. Temperature structure of the grey atmosphere.

PDF**Lecture 6: September 20:**LTE (Maxwellian distribution in velocities, Boltzmann equation, Saha formula).

PDF**Compulsory problems:**[Set 1] (return by October 2).**Lecture 7: October 2:**Stellar Opacity (Bound-bound, bound-free and free-free absorptions).

PDF**Lecture 8: October 4:**Other sources of opacity (H-, He and Metallic absorptions, Scattering, Effect of nongreyness of the temperature structure).

PDF**Lecture 9: October 9:**Rosseland mean opacity, Towards the Model Photosphere (Hydrostatic equilibrium, Gas Pressure, Electron Pressure).

PDF**Lecture 10: October 11:**Towards the Model Photosphere (Radiation pressure, Eddington limit).

PDF**Compulsory problems:**[Set 2] (return by October 16 [Problem 3 is revised, return by October 30, 14:15]).**Lecture 11: October 16:**The Forgotten Chapters (Radiation, Astrophysical, and Eddington Flux; Wavelength dependence of absorption coefficients; Balmer jump).

PDF**Compulsory problems:**[Set 3] (return by October 30, 14:15).**Mid-term exam: October 30.****Lecture 12: November 1:**Spectral lines (Equivalent Width, FWHM, FWZI, Radial Velocity).

PDF**Practical Session: November 6:**Software (Iraf, Dech).

Spectra of stars: Vega, Sun**Info Session: November 13**.

Spectra of stars: Vega, Sun**Lecture 13: November 15:**Spectral line formation (Einstein coefficients).

PDF**Lecture 14: November 22:**Spectral line formation (Natural Line Width, Natural broadening, Doppler broadening, Pressure broadening).

PDF**Lecture 15: November 27:**Spectral line formation (Pressure broadening, Convolution of different broadening processes, Ingis-Teller relation, Rotational and Instrumental broadening).

PDF**Lecture 16: November 29:**Simple line transfer, Schuster-Schwarzschild model, Theory of line formation, Curve of Growth.

PDF**Lecture 17: December 11:**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 18: December 13:**non-LTE (Statistical equilibrium, Two-level approximation, the line source function, LTE versus non-LTE).

PDF**Lecture 19: December 18:**Spectral type sequence. 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