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Be Stars. Nicholas De Lucca. Classification. Spectral Class B Emission lines IR excess Be Main sequence Post main sequence B[e] Supergiant Pre-main sequence Planetary nebulae. M45. Be Stars. First observed 1867 - Angelo Secchi (1818-1878) Active hot star

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Be stars

Be Stars

Nicholas De Lucca


Classification

Classification

  • Spectral Class B

  • Emission lines

  • IR excess

  • Be

    • Main sequence

    • Post main sequence

  • B[e]

    • Supergiant

    • Pre-main sequence

    • Planetary nebulae


Be stars

M45


Be stars1

Be Stars

  • First observed 1867 - Angelo Secchi (1818-1878)

  • Active hot star

  • 20% of all B stars, 60-70% in younger clusters

  • Oblate

  • Strong polar wind

  • High speed rotation


Cassiopeia spectrum h

γCassiopeia Spectrum - Hα


Cassiopeia structure

γCassiopeia - Structure


Variability

Variability

  • Short Term

    • A few minutes or days

    • Photosphere oscillations?

  • Medium Term

    • Few years

    • Moving density pattern

  • Long Term

    • Few decades

    • B -> Be -> Be Shell

    • Reason unknown


Long term variation

Long Term Variation


Long term variation1

Long Term Variation


Rotation

Rotation

  • Keplerian

  • 0.5 Vc > V > 0.9 Vc

  • V > 300 km/s


B e stars

B[e] Stars

  • 1970’s

  • Lower circumstellar density

    • Allows forbidden emission

  • Higher IR excess

  • B[e] phenomenon versus B[e] Star

  • Regions of varying density


B e phenomenon criteria

B[e] Phenomenon Criteria

  • Balmer emission lines

  • Low excitation permitted emission lines

  • [FeII] and [OI] forbidden emission lines in the visual

  • Infrared excess


Forbidden emission lines hd 38489

Forbidden Emission Lines – HD 38489


B e supergiants

B[e] Supergiants

  • L > 104LSun

  • Lower cimcumstellar density due to much larger size

  • Dust forms near edge of disk


Herbig aeb e stars

Herbig AeB[e] Stars

  • Young Stellar Objects (YSO)

  • 2-8 MSun

  • Lack of nuclear burning


B e planetary nebulae

B[e] Planetary Nebulae

  • Ionized red giant gas shells

  • MRG < 8-10 MSun

  • May have [OIII], [SIII], [NeIII]


Summary

Summary

  • Emission Lines

    • Permissible and forbidden

  • Variability

    • Short, medium and long term

  • Circumstellar disk

  • Strong Wind

  • Fast Rotation


References

References

  • Lamers, Henny J. G. L. M.; Zickgraf, Franz-Josef; de Winter, Dolf; Houziaux, Leo; Zorec, Janez, "An improved classification of B[e]-type stars", Astronomy and Astrophysics, v.340, p.117-128 (1998)

  • Michaela Kraus, Marcelo Borges Fernandes, Francisco X. de Ara´ujo, Henny J.G.L.M. Lamers, "The Compact Planetary Nebula B[e] Star Hen 2--90", San Francisco: Astronomical Society of the Pacific, 2006., p.125

  • Stee, P. Active Hot Stars. Observatoria de la Cote d’Azur. 1 Dec. 2006 <http://www.oca.eu/stee/Bemodel.html>

  • Percy, John. “Gamma Cassiopeiae.” Variable Stars. American Association of Variable Star Observers. Oct. 2001 <http://www.aavso.org/vstar/vsots/1001.shtml>

  • Buill, Christian. The Be Stars Atlas. 20 Oct. 2007 <http://www.astrosurf.com/buil/us/bestar.htm>

  • Jensen, Adam. AST 102. 2 Dec. 2006 <http://origins.colorado.edu/~jensenag/teaching/AST102>

  • Thinkquest. <http://library.thinkquest.org/19662/images/eng/pages/model-bohr-3.jpg>


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