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(Referência obtida automaticamente do Web of Science, por meio da informação sobre o financiamento pela FAPESP e o número do processo correspondente, incluída na publicação pelos autores.)

Cyclic variability of the circumstellar disk of the Be star zeta Tauri I. Long-term monitoring observations

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Autor(es):
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Stefl, S. [1] ; Rivinius, Th. [1] ; Carciofi, A. C. [2] ; Le Bouquin, J. -B. [1] ; Baade, D. [3] ; Bjorkman, K. S. [4] ; Hesselbach, E. [4] ; Hummel, C. A. [3] ; Okazaki, A. T. [5] ; Pollmann, E. ; Rantakyroe, F. [6] ; Wisniewski, J. P. [7]
Número total de Autores: 12
Afiliação do(s) autor(es):
[1] European Org Astron Res So Hemisphere, Santiago 19 - Chile
[2] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfericas, BR-05508900 Sao Paulo - Brazil
[3] European Org Astron Res So Hemisphere, D-85748 Garching - Germany
[4] Univ Toledo, Dept Phys & Astron, Toledo, OH 43606 - USA
[5] Hokkai Gakuen Univ, Fac Engn, Toyohira Ku, Sapporo, Hokkaido 0628605 - Japan
[6] AURA, Gemini Observ, So Operat Ctr, La Serena - Chile
[7] Univ Washington, Dept Astron, Seattle, WA 98195 - USA
Número total de Afiliações: 7
Tipo de documento: Artigo Científico
Fonte: Astronomy & Astrophysics; v. 504, n. 3, p. 929-944, SEP 2009.
Citações Web of Science: 43
Resumo

Context. Emission lines formed in decretion disks of Be stars often undergo long-term cyclic variations, especially in the violet-to-red (V/R) ratio of their primary components. The underlying structural and dynamical variations of the disks are only partly understood. From observations of the bright Be-shell star. Tau, the possibly broadest and longest data set illustrating the prototype of this behaviour was compiled from our own and archival observations. It comprises optical and infrared spectra, broad-band polarimetry, and interferometric observations. Aims. The dense, long-time monitoring permits a better separation of repetitive and ephemeral variations. The broad wavelength coverage includes lines formed under different physical conditions, i.e. different locations in the disk, so that the dynamics can be probed throughout much of the disk. Polarimetry and interferometry constrain the spatial structure. All together, the objective is a better understand the dynamics and life cycle of decretion disks. Methods. Standard methods of data acquisition, reduction, and analysis were applied. Results. From 3 V/R cycles between 1997 and 2008, a mean cycle length in Ha of 1400-1430 days was derived. After each minimum in V/R, the shell absorption weakens and splits into two components, leading to 3 emission peaks. This phase may make the strongest contribution to the variability in cycle length. There is no obvious connection between the V/R cycle and the 133-day orbital period of the not otherwise detected companion. V/R curves of different lines are shifted in phase. Lines formed on average closer to the central star are ahead of the others. The shell absorption lines fall into 2 categories differing in line width, ionization/excitation potential, and variability of the equivalent width. They seem to form in separate regions of the disk, probably crossing the line of sight at different times. The interferometry has resolved the continuum and the line emission in Br gamma and HeI 2.06. The phasing of the Br gamma emission shows that the photocenter of the line-emitting region lies within the plane of the disk but is offset from the continuum source. The plane of the disk is constant throughout the observed V/R cycles. The observations lay the foundation for the fully self-consistent, one-armed, disk-oscillation model developed in Paper II. (AU)

Processo FAPESP: 04/07707-3 - Envoltórios circunstelares assimétricos
Beneficiário:Alex Cavaliéri Carciofi
Linha de fomento: Bolsas no Brasil - Pós-Doutorado