11

Be StarsBe Stars

Nicholas De LuccaNicholas De Lucca

22

ClassificationClassification

Spectral Class BSpectral Class B Emission linesEmission lines IR excessIR excess BeBe

Main sequenceMain sequence Post main sequencePost main sequence

B[e]B[e] SupergiantSupergiant Pre-main sequencePre-main sequence Planetary nebulaePlanetary nebulae

33

M45M45

44

Be StarsBe Stars

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

Active hot starActive hot star 20% of all B stars, 60-20% of all B stars, 60-

70% in younger clusters70% in younger clusters OblateOblate Strong polar windStrong polar wind High speed rotationHigh speed rotation

55

γγCassiopeia Spectrum - HCassiopeia Spectrum - Hαα

66

γγCassiopeia - StructureCassiopeia - Structure

77

VariabilityVariability

Short TermShort Term A few minutes or daysA few minutes or days Photosphere oscillations?Photosphere oscillations?

Medium TermMedium Term Few yearsFew years Moving density patternMoving density pattern

Long TermLong Term Few decadesFew decades B -> Be -> Be ShellB -> Be -> Be Shell Reason unknownReason unknown

88

Long Term VariationLong Term Variation

                                                                                 

                                                                                                                  

                                                                                 

                                                                                                                  

                                                                                 

                                                                                                                  

                                                                                 

                                                                                                                  

99

Long Term VariationLong Term Variation

1010

RotationRotation

KeplerianKeplerian

0.50.5 V Vcc > > VV > 0.9 > 0.9 VVcc VV > 300 km/s > 300 km/s r

GMmmV 2

2

1

r

GMmmVc 2

2

1

1111

B[e] StarsB[e] Stars

1970’s1970’s Lower circumstellar densityLower circumstellar density

Allows forbidden emissionAllows forbidden emission Higher IR excessHigher IR excess B[e] phenomenon versus B[e] StarB[e] phenomenon versus B[e] Star Regions of varying densityRegions of varying density

1212

B[e] Phenomenon CriteriaB[e] Phenomenon Criteria

Balmer emission linesBalmer emission lines Low excitation permitted emission linesLow excitation permitted emission lines [Fe[FeIIII] and [O] and [OII] forbidden emission lines in the ] forbidden emission lines in the

visualvisual Infrared excessInfrared excess

1313

Forbidden Emission Lines – HD 38489Forbidden Emission Lines – HD 38489

1414

B[e] SupergiantsB[e] Supergiants

LL > 10 > 1044LLSunSun Lower cimcumstellar Lower cimcumstellar

density due to much density due to much larger sizelarger size

Dust forms near edge of Dust forms near edge of diskdisk

1515

Herbig AeB[e] StarsHerbig AeB[e] Stars

Young Stellar Young Stellar Objects (YSO)Objects (YSO)

2-8 2-8 MMSunSun

Lack of nuclear Lack of nuclear burningburning

1616

B[e] Planetary NebulaeB[e] Planetary Nebulae

Ionized red giant gas shellsIonized red giant gas shells MMRGRG < 8-10 < 8-10 MMSunSun

May have [OMay have [OIIIIII], [S], [SIIIIII], [Ne], [NeIIIIII]]

1717

SummarySummary

Emission LinesEmission LinesPermissible and forbiddenPermissible and forbidden

VariabilityVariabilityShort, medium and long termShort, medium and long term

Circumstellar diskCircumstellar disk Strong WindStrong Wind Fast RotationFast Rotation

1818

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

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

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

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

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

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

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