stellar spectral classification the first step in quantitative spectral analysis part i and ii n.
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Stellar Spectral classification The First Step in Quantitative Spectral Analysis PART I AND II. Ewa Niemczura Astronomical Institute , University of Wrocław eniem@astro.uni.wroc.pl. References. Book : „ Stellar spectral classification ”, R.O. Gray & C.J. Corbally

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Stellar Spectral classification The First Step in Quantitative Spectral Analysis PART I AND II


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    1. StellarSpectralclassificationThe First Step in Quantitative Spectral AnalysisPART I AND II Ewa Niemczura AstronomicalInstitute, University of Wrocław eniem@astro.uni.wroc.pl

    2. References • Book: „Stellarspectralclassification”, R.O. Gray & C.J. Corbally • Lecture and paper: „Stellar spectral classification”. R.O. Gray, Spring School of Spectroscopic Data Analyses, Wrocław 2013 • http://stellar.phys.appstate.edu/Standards/

    3. Classification – essentialactivityof Science

    4. How to do spectralclassification? Viadirect comparison with spectra ofstandard stars; • Spectralregion/resolution are of secondary importance; • Spectraltype and luminosityclassare fundamental data onlyifno theoryorother data is used; • Standard stars: Anchorpoints, Primarystandards, Secondarystandards; • Method: visual (orauthomatical); we needcomparisonstars: when observingyourstars, observe alsofew standards; • Complicated and iterativeprocess.

    5. Whyspectralclassificationisimportant? Independent source of information and the beginning point for further spectral analysis: • locatestar in theH-R diagram; • firstestimate of Teff, logg,[m/H], rotationvelocity; • Identification ofchemicallypeculiar stars and astrophysicalyinterestingobjects; • useful “reality check” to an analysis based on stellar atmosphere theory.

    6. O Be A Fine Girl Kiss Me

    7. Stellarspectralclassification

    8. O and B-typestars • O-typestars: • Teff from ~28000 to ~50000 K • M from 16 to ~100 Msun • B-typestars: • Tefffrom ~10000 to ~28000 K • M from 2to ~16 Msun

    9. Spectra of O- and B-typestarsOptical part H He C N O Ne Mg Al Si S Fe

    10. SpectralclassificationOptical part – spectraltype • Balmer lines of hydrogen • Helium lines: He I (B-typestars) • Helium lines: He II (O-typestars)

    11. SpectralclassificationO-typestars • Helium lines: He I • Helium lines: He II • Balmerlines of hydrogen

    12. Spectralclassification (B-typestars)Optical part – spectraltype

    13. Spectralclassification (B-typestars)Optical part – spectraltype

    14. Spectralclassification(B-typestars)Optical part – spectraltype

    15. Spectralclassification (B-typestars)Optical part – spectraltype

    16. SpectralclassificationOptical part – spectraltype • Helium lines: He I(from O-typestars, maximum at a spectraltype of B2; disappearingat a spectraltype of A0) • Helium lines: He II (O-typestars) • Balmer lines of hydrogen(maximum at a spectraltype of A2) • Spectralclassification: He I,II and Balmer lines • In case of B-typestars: helium abundanceanomalies • Solution:silicon lines ratios: Si III/Si II and Si IV/Si III

    17. Spectralclassification (B-typestars)Optical part – spectraltype

    18. Spectralclassification (B-typestars)Optical part – spectraltype

    19. SpectralclassificationOptical part – spectraltype • Helium lines: He IHelium lines: He II • Balmer lines of hydrogenSpectralclassification: He I and Balmer lines • Helium abundanceanomalies • Silicon lines ratios: Si III/Si II and Si IV/Si III • Balmer lines and Si lines areluminositysensitive • Mg II (4481 Å): ratio He I (4471 Å)/Mg II (4481 Å)

    20. Spectralclassification (B-typestars)Optical part – spectraltype

    21. Spectralclassification (B-typestars)Optical part – spectraltype

    22. SpectralclassificationOptical part – spectraltype • Helium lines: He IHelium lines: He II • Balmer lines of hydrogenSpectralclassification: He I and Balmer lines • Helium abundanceanomalies • Silicon lines ratios: Si III/Si II and Si IV/Si III • Balmer lines and Si lines areluminositysensitive • Mg II (4481 Å): ratio He I (4471 Å)/Mg II (4481 Å)

    23. SpectralclassificationOptical part – luminosityclass • Balmer lines of hydrogen(luminositysensitivityisgreatest in the late B-typestars)

    24. SpectralclassificationOptical part – luminosityclass • Balmer lines of hydrogen(luminositysensitivityisgreatest in the late B-typestars) • B-typestars: O II lines(increase in strength with increasingluminosity) Ratios: O II with Balmer lines and the He I lines

    25. Spectralclassification (B-typestars)Optical part – luminosityclass

    26. SpectralclassificationOptical part – luminosityclass • Balmer lines of hydrogen(luminositysensitivityisgreatest in the late B-typestars) • O II lines(increase with strength with increasingluminosity) • Rations: O II with Balmer lines and the He I lines • But: CNO peculiarities • Solution: ratios of silicon lines to He I

    27. SpectralclassificationOptical part – luminosityclass

    28. SpectralclassificationOptical part – luminosityclass • Balmer lines of hydrogen(luminositysensitivityisgreatest in the late B-typestars) • O II lines(increase with strength with increasingluminosity) • Rations: O II with Balmer lines and the He I lines • But: CNO peculiarities • Solution: ratios of silicon lines to He I • N II (3995 Å)

    29. SpectralclassificationOptical part – luminosityclass

    30. Spectralclassification (O-typestars)Optical part – luminosityclass • N III • Si IV • S IV

    31. Spectralclassification (O-typestars)Optical part – luminosityclass • Balmer lines • Si IV / H • Si IV/ He I

    32. SpectralclassificationOptical part Spectralclassification: iterativeprocess Spectraltype, B-typestars: • Balmer lines • Helium lines • Other lines ifnecessary Spectraltype, O-typestars: He II lines Luminosityclass: Balmer lines + metal lines Warning: chemicallypeculiarstars!

    33. Chemicallypeculiarstars B-typestars Helium-strongstars, He-s • Spectraltypes: B3 orearlier • Strong lines of He I

    34. Chemicallypeculiar B stars: He-strong • Spectraltypes: B3 orearlier • Strong lines of He I • Strongmagneticfields • Photometric and spectroscopicvariability– oblique rotator model (magneticaxisisinclined with respect to the rotationalaxis).

    35. Oblique rotator model: magneticaxisisinclined with respect to the rotationalaxis.

    36. Chemicallypeculiar B-typestars Helium-weakstars, He-w • Spectraltypes: B3 orlater • Weaklines of He I • Variability • Magnetic field

    37. Chemicallypeculiar B-typestars Helium-weak star subclasses: • Si stars ( enhanced Si II lines) • PGastars • SrTistars

    38. Chemicallypeculiar B-typestars Helium-weakstars, He-w • Spectraltypes: B3 orlater • Weak lines of He I • Variability • Magneticfield Helium-weakstarssubclasses: • Si stars(enhancedSi II lines, hotterthanclassicalAp Si stars) • SrTistars(enhancedSr and Ti, lines, hotterthanclassicalApSr stars) Magnetic He-weak B-typestars – hot end of the magneticApstars

    39. Chemicallypeculiar B-typestars Helium-weakstars, He-w • Spectraltypes: B3 orlater • Weak lines of He I • Variability • Magneticfield Helium-weakstarssubclasses: • Si stars(enhancedSi II lines, hotterthanclassicalAp Si stars) • SrTistars(enhancedSr and Ti lines, hotterthanclassicalApSr stars) • PGastars(enhanced P and Ga lines, hot end of HgMnstars, no detection of magnetic field)

    40. Chemicallypeculiar B-typestars HgMn (mercury-manganese) stars: • Spectraltypes: B7-B9, luminosityclass III-V • Strong lines of Hg II and Mn II; mild helium deficienciesand otherpeculiarities • Magnetic field • Periodicspectralvariations(non-uniform distribution of abundances on the stellarsurface, so the presence of a magnetic field) • Connection with hot-Am stars?

    41. Chemicallypeculiar B-typestars • Helium-strong • Helium-weak • Si • SrTi • PGa • HgMn • Bp stars • Si II • Cr II • Sr II • Eu II

    42. Chemicallypeculiar B-typestarsSummary

    43. Chemicallypeculiar B-typestars: 3He – 4He • Peculiarprofiles of helium lines: 3He – 4He stars 3He 4He

    44. Chemicallypeculiar B-typestars: 3He – 4He Bohlender (2005)

    45. CP starson H-R diagram Bohlender (2005)

    46. A and F-typestars • A-typestars: • Teff from ~7500 to ~10000K; M from ~1.4 to ~2.1 Msun • F-typestars: • Tefffrom ~6000 to ~7500K; Mfrom ~1.04 to ~1.4 Msun

    47. 10000 K 9000 K 8000 K 7000 K 6000 K