Spektrální diagnostika B[e] hvězd

• Thesis title in Czech: Spektrální diagnostika B[e] hvězd
• Thesis title in English: Spectroscopic diagnosis of B[e] stars
• Key words: spektrální diagnostika, látka v okolí hvězd, horké hvědy
• English key words: spectroscopic diagnosis, circumstellar matter, hot stars
• Academic year of topic announcement: 2018/2019
• Thesis type: dissertation
• Thesis language: čeština
• Department: Astronomical Institute of Charles University (32-AUUK)
• Supervisor: doc. Mgr. Daniela Korčáková, Ph.D.
• Author: hidden - assigned and confirmed by the Study Dept.
• Date of registration: 11.09.2019
• Date of assignment: 11.09.2019
• Confirmed by Study dept. on: 02.10.2019

Guidelines

The B[e] phenomenon is a collective taxonomical designation for hot (B-type) stars, whose spectra show strong emission lines of heavy elements from the forbidden transitions of atoms at low ionisation stages. They also have a strong infrared excess that is attributed to the hot dust.

The phenomenon is observed in only a small number of cases of different types. Lamers et al. (1998) identified five different classes - supergiants (sgB[e]), pre-main sequence stars (HAeB[e]), compact planetary nebulae (cPNB[e]), symbiotic stars (SymB[e]), and unclassified stars. Later, Miroshnichenko et al. (2007) recognised that almost all unclassified stars have similar properties and introduced a new group called FS CMa objects.

The focus of the thesis is the later one, FS CMa group. While a raw model for the original four groups has been already established, the nature of FS CMa stars remains unknown. One of the key steps is to determine stars from FS CMa list which has been wrongly classified and belongs to another group. Especially, the distinction of proto-planetary nebulae (post-AGB stars) from FS CMa stars has benefit not only for the determination of the nature of FS CMa stars, but also for the study of fast phases of low-mass stellar evolution. This episode is observationally not well described. One of the reason is the analysis of spectra of such objects, which is very complicated in the case where structured nebula and central stars are both linked together.

As a first task during the first year, the student will search for the proto-planetary candidates in the list of FS CMa stars and write a proposal for the large telescopes in order to obtain high-quality spectra. She/he will also work on the spectral analysis of known proto-planetary nebula between FS CMa candidates - MWC 939 and OY Gem, which is a compact planetary nebulae with the B[e] phenomenon. The basic spectral analysis of newly obtained spectra, as well as archive ones, will continue in the next year, when the student has to start the work on modelling of synthetic spectra of such objects using a publicly available code CLOUDY. The student will summarize her/his results in the paper to A&A.

References

Dopita, M.A., Sutherland, R.S. Astrophysics of the Diffuse Universe (Springer), 3rd edition, 2003
Emerson, D., 1999, "Interpreting Astronomical Spectra", John Wiley & Sons
Gray, D.F., ``The Observation and Analysis of Stellar Photospheres'', Cambridge University Press, 2005
Jaschek, C., Andrillat, Y., Jaschek, M., 1996, A&AS 117, 281
Lamers, H.J.G.L.M., Zickgraf, F.J., de Winter, D., Houziaux, L., Zorec, J., 1998, A&A 340, 117
Mihalas, D. Stellar atmosheres (San Francisco: Freeman), 2nd edition, 1978
Miroshnichenko, A. S. 2007, ApJ, 667, 497
Miroshnichenko, A. S., Manset, N., Kusakin, A. V., et al. 2007, ApJ, 671, 828
Osterbrock, D. E. & Ferland, G. J. 2005, "Astrophysics Of Gaseous Nebulae And Active Galactic Nuclei" (University Science Books, 2nd edition)
Shore, S.N.The Tapestry of Modern Astrophysics (Wiley Interscience), 2003
Stars with the B[e] Phenomenon. ASP Conference Series, Vol. 355, M. Kraus & A. Miroshnichenko eds., San Francisco: Astronomical Society of the Pacific, 2006
The B[e] Phenomenon: Forty Years of Studies. ASP Conference Series, Vol. 508., A. Miroshnichenko, S. Zharikov, D. Korčáková & M. Wolf San Francisco: Astronomical Society of the Pacific, 2017