1. Be Stars
Nicholas De Lucca

2. Classification B[e] Spectral Class B Emission lines IR excess Be
Main sequence
Post main sequence
B[e]
Supergiant
Pre-main sequence
Planetary nebulae

3. M45

4. 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

5. γCassiopeia Spectrum - Hα

6. γCassiopeia - Structure

7. Variability Short Term Medium Term Long 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

8. Long Term Variation
                                                                                 
                                                                                                                  

9. Long Term Variation

10. Rotation
Keplerian
0.5 Vc > V > 0.9 Vc
V > 300 km/s

11. B[e] Stars 1970’s Lower circumstellar density Higher IR excess
Allows forbidden emission
Higher IR excess
B[e] phenomenon versus B[e] Star
Regions of varying density

12. B[e] Phenomenon Criteria
Balmer emission lines
Low excitation permitted emission lines
[FeII] and [OI] forbidden emission lines in the visual
Infrared excess

13. Forbidden Emission Lines – HD 38489

14. B[e] Supergiants L > 104LSun
Lower cimcumstellar density due to much larger size
Dust forms near edge of disk

15. Herbig AeB[e] Stars Young Stellar Objects (YSO) 2-8 MSun
Lack of nuclear burning

16. B[e] Planetary Nebulae
Ionized red giant gas shells
MRG < 8-10 MSun
May have [OIII], [SIII], [NeIII]

17. Summary Emission Lines Variability Circumstellar disk Strong Wind
Permissible and forbidden
Variability
Short, medium and long term
Circumstellar disk
Strong Wind
Fast Rotation

18. 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 (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 <
Percy, John. “Gamma Cassiopeiae.” Variable Stars. American Association of Variable Star Observers. Oct <
Buill, Christian. The Be Stars Atlas. 20 Oct <
Jensen, Adam. AST Dec <
Thinkquest. <