 Wolf-Rayet Stars & the Luminous Blue Variables 2014/11/12 Wednesday Luqian Wang.

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Presentation transcript:

 Wolf-Rayet Stars & the Luminous Blue Variables 2014/11/12 Wednesday Luqian Wang

Outline  Definition/General properties  History  Classification: Optical/UV-FUV/Infrared  Luminous Blue Variables (LBVs)

Definitions/General Properties  Definition: Hot, luminous stars whose spectacular spectra are dominated by emission lines formed in a massive stellar wind  Evolved descendent of the most massive star  Mass: [10,25] Msun, T: [3E4, 2E5] K  Mass loss rate: ~E-5 Msun/year  Nitrogen sequence (WN), Carbon sequence (WC)  End of lives: supernova explosion

History  1837, Charles Wolf & Georges Rayet  Cygnus: HD (Vogel,1883), HD192103, HD  Carlye Beals, Dominion Astrophysical Observatory (1934,1938)  Smith (1968)  Smith, Shara & Moffat (1996)

Outline  Definition/General properties  History  Classification: Optical/UV-FUV/Infrared  Luminous Blue Variables (LBVs)

WN classification  Ionization state of N predominates in the spectrum  (P443, Gray & Corbally )  Hamann, Koesterke & Wessolowski (1995): a – absorption lines; -w/-s – weak/strong emission lines (EW of He II-5412, 37 Angstrom)

WC classification  Line judgments:  Crowther et al. (1998) : WC8-WC11  Please see Table 11.2

WO classification  Judgment lines:  Kingsburgh, Barlow & Storey (1995) Crowther et al. (1998)  Result of high-ionization of oxygen, rather than increased O abundance  High-ionization extension of WC stars  Please see Table 11.3

Outline  Definition/General properties  History  Classification: Optical/UV-FUV/Infrared  Luminous Blue Variables (LBVs)

Ultraviolet : WN  WR stars emit most of their radiation in UV/FUV  International Ultraviolet Explorer ( IUE ): wavelength: [1150,3250] Angstrom low resolution: ~6.0 Angstrom  blended lines

Ultraviolet: WC  Line indicators:

Far Ultraviolet (FUV)  Far Ultraviolet Spectroscopic Explorer ( FUSE ) wavelength: [905,1188] Angstrom Resolution: ~0.05 Angstrom  Issue: < 1000 Angstrom, interstellar absorptions.

FUSE WN

FUSE WC

Outline  Definition/General properties  History  Classification: Optical/UV-FUV/Infrared  Luminous Blue Variables (LBVs)

Late WN

Early WN

Late WC

Early WC

Outline  Definition/General properties  History  Classification: Optical/UV-FUV/Infrared  Luminous Blue Variables (LBVs)

Luminous Blue Variables (LBVs)  LBV (S Doradus): Evolved, massive, and extremely luminous supergiant that is subject to instabilities that result in eruptions of various sorts.  e.g. eta Carinae, P Cygni  Eruption  optical thick, expanded atmosphere, i.e. “Pseudo photosphere”  Quiescent (minimum light state) : T>15,000 K Eruption (maximum light state): T~[7000,8000] K

LBVs on HR-diagram 

O, WR, & LBV relation?  WR stars and LBVs: high mass loss rate, high luminosities, & close association w/star formation  Evolutionary scenario:

Thank you!