1. Stellar Atmospheres: Motivation 1 Stellar Atmospheres: Literature Dimitri Mihalas –Stellar Atmospheres, W.H. Freeman, San Francisco Albrecht Unsöld –Physik der Sternatmosphären, Springer Verlag (in German) Rob Rutten –Lecture Notes Radiative Transfer in Stellar Atmospheres http://www.fys.ruu.nl/~rutten/node20.html

2. Stellar Atmospheres: Motivation 2 Why physics of stellar atmospheres? Physics Stellar atmospheres as laboratories Plasma-, atomic-, and molecular physics, hydrodynamics, thermodynamics Basic research Technical application Astronomy Spectral analysis of stars Structure and evolution of stars Galaxy evolution Evolution of the Universe

3. Stellar Atmospheres: Motivation 3 Magnetic fields in white dwarfs and neutron stars Shift of spectral lines with increasing field strength

4. Stellar Atmospheres: Motivation 4 Hertzsprung Russell Diagram L~R 2 T 4 eff 100 R  1 R  =700000Km 0.01 R  4 10 26 W 5800K

5. Stellar Atmospheres: Motivation 5 Massive stars

6. Stellar Atmospheres: Motivation 6 Chemical evolution of the Galaxy Carretta et al. 2002, AJ 124, 481

7. Stellar Atmospheres: Motivation 7 SN movie

8. Stellar Atmospheres: Motivation 8 SN Ia

9. Stellar Atmospheres: Motivation 9 SN Ia cosmology  M,   0, 1 0.5, 0.5 1, 0 1.5, -.5 0, 0 1, 0 2, 0 Redshift z

10. Stellar Atmospheres: Motivation 10 SN Ia Kosmologie  

11. Stellar Atmospheres: Motivation 11 Uranium-Thorium clock

12. Stellar Atmospheres: Motivation 12 Stellar atmosphere – definition From outside visible, observable layers of the star Layers from which radiation can escape into space –Dimension Not stellar interior (optically thick) No nebula, ISM, IGM, etc. (optically thin) But: chromospheres, coronae, stellar winds, accretion disks and planetary atmospheres are closely related topics

13. Stellar Atmospheres: Motivation 13 Sonne

14. Stellar Atmospheres: Motivation 14 Fraunhofer lines

15. Stellar Atmospheres: Motivation 15 Spectrum - schematically Intensity Wavelength / nm

16. Stellar Atmospheres: Motivation 16 Spectrum formation

17. Stellar Atmospheres: Motivation 17 Formation of absorption lines Interior outer boundary observer continuum line center continuum stellar atmosphereintensity

18. Stellar Atmospheres: Motivation 18 Line formation / stellar spectral types spectral line temperature structure interior flux wavelength temperature depth / km

19. Stellar Atmospheres: Motivation 19 The spectral types on the main sequence O B A F G K M O5 B4 O7 B6 A1 A5 A8 A9 F8 G2 G5 G8 A7 F3

20. Stellar Atmospheres: Motivation 20 Die Spektraltypen der Hauptreihe O B A F G K M F6 F8 G2 G5 G8 A7 F3 G6 G9 K4 K5 F8 G1

21. Stellar Atmospheres: Motivation 21 Classification scheme M9 L3 L5 L8

22. Stellar Atmospheres: Motivation 22 Classification scheme T dwarfs

23. Stellar Atmospheres: Motivation 23 Stellar atmosphere – definition From outside visible, observable layers of the star Layers from which radiation can escape into space –Dimension Not stellar interior (optically thick) No nebula, ISM, IGM, etc. (optically thin) But: chromospheres, coronae, stellar winds, accretion disks and planetary atmospheres are closely related topics

24. Stellar Atmospheres: Motivation 24 Optical telescopes Calar Alto (Spain) 3.5m telescope

25. Stellar Atmospheres: Motivation 25 Optical telescopes ESO/VLT

26. Stellar Atmospheres: Motivation 26 Why is it important? UV / EUV observations flux wavelength / Å

27. Stellar Atmospheres: Motivation 27 UV/optical telescopes HST

28. Stellar Atmospheres: Motivation 28 X-ray telescopes XMM

29. Stellar Atmospheres: Motivation 29 Gamma-ray telescopes INTEGRAL

30. Stellar Atmospheres: Motivation 30 Infrared observatories ISO JWST

31. Stellar Atmospheres: Motivation 31 Sub-mm telescopes

32. Stellar Atmospheres: Motivation 32 Radio telescopes 100m dish at Effelsberg

33. Stellar Atmospheres: Motivation 33 Stellar atmosphere – definition From outside visible, observable layers of the star Layers from which radiation can escape into space –Dimension Not stellar interior (optically thick) No nebula, ISM, IGM, etc. (optically thin) But: chromospheres, coronae, stellar winds, accretion disks and planetary atmospheres are closely related topics

34. Stellar Atmospheres: Motivation 34 PN – NGC6751 - HST

35. Stellar Atmospheres: Motivation 35 Planetary nebula spectrum

36. Stellar Atmospheres: Motivation 36 ISM spectrum

37. Stellar Atmospheres: Motivation 37 Quasar + IGM spectrum

38. Stellar Atmospheres: Motivation 38 Stellar atmosphere – definition From outside visible, observable layers of the star Layers from which radiation can escape into space –Dimension Not stellar interior (optically thick) No nebula, ISM, IGM, etc. (optically thin) But: chromospheres, coronae, stellar winds, accretion disks and planetary atmospheres are closely related topics

39. Stellar Atmospheres: Motivation 39 Eta Carinae - HST

40. Stellar Atmospheres: Motivation 40 Stellar wind spectrum

41. Stellar Atmospheres: Motivation 41 Formation of wind spectrum (P Cygni line profiles)

42. Stellar Atmospheres: Motivation 42 Stellar winds – P Cyg profiles

43. Stellar Atmospheres: Motivation 43 Accretion disks

44. Stellar Atmospheres: Motivation 44 AM CVn disk spectrum models

45. Stellar Atmospheres: Motivation 45 Temperature structure of an accretion disk Distance from star [km] Height [km]

46. Stellar Atmospheres: Motivation 46 Planetary atmospheres

47. Stellar Atmospheres: Motivation 47 Quantitative spectral analyses – what can we learn? Shape of line profile: Temperature FilmFilm Density FilmFilm Abundance FilmFilm Rotation Turbulence Magnetic field Line position: Chemical composition Velocities Redshift Temporal variation: Companion Surface structure Spots Pulsation

48. Stellar Atmospheres: Motivation 48 Zeeman effect

49. Stellar Atmospheres: Motivation 49 Magnetic fields L l optical spectrum circular polarization position of line components spectrum of a white dwarf (PG 1658+440) with field strength of about 5 MG

50. Stellar Atmospheres: Motivation 50 Magnetic fields L White dwarf Grw+70 8247 B=300MG optical spectrum Circular polarization position of line components

51. Stellar Atmospheres: Motivation 51 Extrasolar planets

52. Stellar Atmospheres: Motivation 52 Velocity fields Wavelength / Å Distance / 1000 km ~ 0.01Å Solar disk time / min distance / 1000km

53. Stellar Atmospheres: Motivation 53 Non-radial pulsation modes

54. Stellar Atmospheres: Motivation 54 Time resolved spectroscopy

55. Stellar Atmospheres: Motivation 55 Time dependent line profiles Time Flux

56. Stellar Atmospheres: Motivation 56 Doppler tomography

57. Stellar Atmospheres: Motivation 57 Summary – stellar atmospheres theory The atmosphere of a star contains less than one billionth of its total mass, so, why do we care at all? The atmosphere of a star is that what we can see, measure, and analyze. The stellar atmosphere is therefore the source of information in order to put a star from the color-magnitude diagram (e.g. B-V,m v ) of the observer into the HRD (L,T eff ) of the theoretician and, hence, to drive the theory of stellar evolution. Atmosphere analyses reveal element abundances and show us results of cosmo-chemistry, starting from the earliest moments of the formation of the Universe. Hence, working with stellar atmospheres enables a test for big-bang theory. Stars are the building blocks of galaxies. Our understanding of the most distant (hence most early emerged) galaxies, which cannot be resolved in single stars, is not possible without knowledge of processes in atmospheres of single stars. Work on stellar atmospheres is a big challenge. The atmosphere is that region, where the transition between the thermodynamic equilibrium of the stellar interior into the empty blackness of space occurs. It is a region of extreme non-equilibrium states.

58. Stellar Atmospheres: Motivation 58 Summary – stellar atmospheres theory Important source of information for many disciplines in astrophysics –research for pure knowledge, contribution to our culture –ambivalent applications (e.g. nuclear weapons) Application of diverse disciplines –physics –numerical methods Still a very active field of research, many unsolved problems –e.g. dynamical processes