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A New Group of Dust-Forming Hot Stars

A New Group of Dust-Forming Hot Stars. Anatoly Miroshnichenko. Pulkovo Observatory (Saint-Petersburg, Russia) Max-Planck-Institut fur Radioastronomie (Bonn, Germany) University of Toledo (Ohio, USA). Collaborators. Main Subject. Dust-Forming Stars.

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A New Group of Dust-Forming Hot Stars

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  1. A New Group of Dust-FormingHot Stars Anatoly Miroshnichenko Pulkovo Observatory(Saint-Petersburg, Russia) Max-Planck-Institut fur Radioastronomie (Bonn, Germany) University of Toledo (Ohio, USA)

  2. Collaborators

  3. Main Subject Dust-Forming Stars circumstellar interstellar circumstellar Hot stars Teff 10000 K + Shielding from UV Colliding Winds Cool Stars Teff ~ 3000 K + Strong Outflow Dust Tsub ~ 1500 K AGB & post-AGB WR, LBV с L/L > 105

  4. Outline • Early-Type Stars with Circumstellar Dust • B[e] Stars • Properties of B[e] Stars with Warm Dust • Search for New Candidates and Results of the Initial Observations • Nature and Evolutionary State • Conclusions

  5. Objects with Circumstellar Dust which Include a Hot Star • Herbig Ae/Be stars (warm & cold dust) • Vega-type stars(cold dust) • Symbiotic Stars (M-giant + OB-subdwarf, white dwarf, or neutron star; warm dust) • VV Cep stars (M-supergiant + OB dwarf ?; warm dust) • Wolf-Rayet stars (carbon-richor binary;warm dust) • Luminous Blue Variables (cold dust) • Proto-Planetary & Planetary Nebulae(cold dust) • B[e] stars

  6. Discovery:Allen& Swings (1976, A&A, 47, 293) 65 objects with forbidden lines and IRexcesses at=2 m Possible explanations for the phenomenon: Formation of a Planetary Nebula Interaction of an OB star with a cool companion Direct ejection of matter by a massive OB star B[e] Stars: History of Studies Follow up classification:Herbig Ae/Be stars(7), LBV(3), PNe (17),symbiotic (8), supergiants (7) 28 objects – uncertain classification

  7. Additions and Systematization Lists of similar objects • Carlson & Henize (1979, Vistas in Astronomy, 23 , 213): 20 early-type stars with strong emission-line spectra • Dong & Hu (1991, Chin. A&A, 15, 275): ~200 early-type stars with strong IR-excesses (IRAS,V-[25] > 8 mag) Systematization Attempt Lamers et al. (1998, A&A, 340, 117) – 5 categories of B[e] stars: sgB[e], pmsB[e], cPNB[e], SymbB[e],unclB[e] New group ofunclB[e] – B[e] stars with warm dust B[e]WD

  8. IRAS color-color diagram  - B[e]WD,  - Ае/Ве stars, - Vega-type stars, - symbiotic stars, + - VV Cep

  9. B[e] Stars with Warm Dust(B[e]WD) Selection Criteria: Spectra: early-type + strong Balmer emission lines IRAS colors: 0.5 < lg F12/F25 < +0.1 1.1 < lg F60/F25 < 0.3 Presentation as a group: Sheikina, Miroshnichenko, & Corporon 1999 (IAU Coll. 175, Alicante, Spain) - 11 objects Miroshnichenko, Bjorkman, Chentsov, Klochkova 2002 (IAU Coll. 187, Florida, USA) - 19 objects Miroshnichenko et al. 2004 (203 AAS Meeting, Atlanta, USA) – 19 objects + 28 candidates

  10. Observations

  11. Properties of B[e]WD

  12. Spectral Energy Distribution

  13. Photometric Properties Frequently observed objects: HD 45677, HD 50138, MWC 300, MWC 342, CI Cam • Variability Types: • Short-term irregular : V ~ 0.1 – 0.5 mag • Long-term gradual brightness changes : V ~ 0.5 – 2 mag (MWC 342, HD 45677) • Short-term outbursts : V ~ 3 mag (CI Cam, 1998 March 31) • Cyclic: from weeks to years • Near-IR variations: K ~ 0.5 mag

  14. H line profiles are mostly double-peaked Single- or double-peaked narrow metallic emission lines(FWHM ~ 100 km s-1) Spectral Properties • Strong and variable Balmer emission lines • Forbidden lines [O I] 6300 & 6364A, [N II] 5577, 6348, & 6384A, sometimes[S III] 6312A

  15. Spectrral Variations

  16. H Line Profiles

  17. Absorption Lines

  18. IR Spectra

  19. Basic Physical Parameters • Spectral Type of the Hot Companion: O9-B8 • Spectral Type of the Cool Companion : F, K • Initial Mass: 2 - 40 M • Luminosity: 500 – 106 L • Circumstellar Gas distribution: disk-like • Circumstellar Dust distribution: not clear (probably circumbinary disk)

  20. Hertzsprung-Russell Diagram

  21. Nature and Evolutionary State • Majorityof (all?) objects – Main-Sequence and after Known Binary systems: • MWC 623: B2 V + K2 III (Zickgraf 2001, A&A, 375, 122) • CI Cam: B[e] sg + black hole? (Miroshnichenko et al. 2002, A&A, 390, 627) • AS 381: B1 I + K II-III (Miroshnichenko et al. 2002, A&A, 383, 171) • V669 Cep: B5 V + K (Miroshnichenko et al. 2002, A&A, 388, 563) • HD 327083: B1 I + F I (Miroshnichenko et al. 2003, A&A, 406, 673) Suspected Binaries: • MWC 342 (Miroshnichenko & Corporon 1999, A&A, 349, 126) • MWC 657 (Miroshnichenko et al. 2000, A&AS, 147, 5) • HD 85567 & Hen 1398 (Miroshnichenko et al. 2001, A&A, 371, 600) • MWC 300 (Miroshnichenko et al. 2004, A&A, 417, 731) Objects with a Controversial State: • HD 45677 & HD 50138 – suggested Herbig Ве stars

  22. Enlarging the Group Basis for a new search forB[e]WD inthe IRAS catalogs • Stars of the main group are relatively bright V ~ 912 mag, K ~ 37 mag, [12m]~ 03.5 mag. TheIRAS sensitivity limit : ~ 6 mag • Large range of the luminosities • Release of the deep sky surveys in 2003:2MASS(JHK) and USNO-B1.0 (5 non-standard optical bands)

  23. Search Strategy & Difficulties Selection criteria • Color-indices[12][25] &[25][60] • Close positions in theIRAS &2MASS catalogs • Selection of the brightest2MASSobject in the IRAS error box • Positional coincidence in the2MASS &USNO catalogs • Difficulties • Selection criteria are only positional & photometric • Separation of reddened hot stars from cool stars • Confusion withRV Tau stars

  24. New Photometric Criterion  B[e]WD & new candidates  - RV Tau; + - cool stars

  25. Search Results •  4500 IR sources was found in the B[e]WD box • 60 objects satisfying the selection criteria were found among 2500 objects with b  50 •  20 objects are thrown out after comparison with dusty RV Tau stars • Initial observations of 40 B[e]WD candidates have been started: • Multicolor optical photometry • Optical spectroscopy of low- and high-resolution • Low-resolution IR spectroscopy

  26. Results of the Initial ObservationsSeptember 2003 – April 2004 Photometry • (WBVR, UBVRI) - 10 objects Spectroscopy • DSO : 38005600 A, R~1800 – 10 objects • БТА:52006600 A, R~60000 – 2 objects • CFHT : H, SiII 6347, Na D, R~100000 – 11objects • Lick Obs. :0.8  2.5m, R~1300 – 5objects • NASA IRTF :3 – 14 m, R~100 – 2objects It is shown that8objects are indeedB/A stars 2 new emission-line objects have been found

  27. New Objects IRAS 00470+6429 BTA USNO, 2MASS, IRTF

  28. New Objects CFHT

  29. Positional Distribution  - main group objects,  - new candidates

  30. Conclusions • A new large group (61 objects to date) of hot stars with circumstellar dust is discovered • Dust formation seems to be eitheron-going or has stopped recently • Objects:either binary systems undergoing a rapid mass exchange orsingle stars with unusually strong winds • Investigation of the group may lead tonew ideas forevolutionary theories of single/binary starsand refinement of our understanding of dist formation

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