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New activity in the large circumstellar disk of the Be-shell star 48 Librae

Texto completo
Stefl, S. [1] ; Le Bouquin, J. -B. [2] ; Carciofi, A. C. [3] ; Rivinius, T. [1] ; Baade, D. [4] ; Rantakyroe, F. [5]
Número total de Autores: 6
Afiliação do(s) autor(es):
[1] European Org Astron Res So Hemisphere, Santiago 19 - Chile
[2] UJF Grenoble 1, CNRS INSU, IPAG, UMR 5274, Grenoble - France
[3] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508900 Sao Paulo - Brazil
[4] European Org Astron Res So Hemisphere, D-85748 Garching - Germany
[5] AURA, So Operat Ctr, Gemini Observ, La Serena - Chile
Número total de Afiliações: 5
Tipo de documento: Artigo Científico
Fonte: Astronomy & Astrophysics; v. 540, APR 2012.
Citações Web of Science: 9

Aims. Spectroscopic, polarimetric, and high spectral resolution interferometric data covering the period 1995-2011 are analyzed to document the transition into a new phase of circumstellar disk activity in the classical Be-shell star 48 Lib. The objective is to use this broad data set to additionally test disk oscillations as the basic underlying dynamical process. Methods. The long-term disk evolution is described using the V/R ratio of the violet and red emission components of H alpha and Br gamma, radial velocities and profiles of He I and optical metal shell lines, as well as multi-band BVRI polarimetry. Single-epoch broad-band and high-resolution interferometric visibilities and phases are discussed with respect to a classical disk model and the given baseline orientations. Results. Spectroscopic signatures of disk asymmetries in 48 Lib vanished in the late nineties but recovered some time between 2004 and 2007, as shown by a new large-amplitude and long-duration V/R cycle. Variations in the radial velocity and line profile of conventional shell lines correlate with the V/R behavior. They are shared by narrow absorption cores superimposed on otherwise seemingly photospheric He I lines, which may form in high-density gas at the inner disk close to the photosphere. Large radial velocity variations continued also during the V/R-quiet years, suggesting that V/R may not always be a good indicator of global density waves in the disk. The comparison of the polarization after the recovery of the V/R activity shows a slight increase, while the polarization angle has been constant for more than 20 years, placing tight limits on any 3-D precession or warping of the disk. The broad H-band interferometry gives a disk diameter of (1.72 +/- 0.2) mas (equivalent to 15 stellar radii), position angle of the disk (50 +/- 9)degrees and a relatively low disk flattening of 1.66 +/- 0.3. Within the errors the same disk position angle is derived from polarimetric observations and from photocenter shifts across Br gamma. The high-resolution interferometric visibility and phase profiles show a double or even multiple-component structure. A preliminary estimate based on the size of the Br gamma emitting region indicates a large diameter for the disk (tens of stellar radii). Overall, no serious contradiction between the observations and the disk-oscillation model could be construed. (AU)

Processo FAPESP: 10/19029-0 - Modelos tridimensionais de transporte radiativo: uma ponte entre teoria e observações
Beneficiário:Alex Cavaliéri Carciofi
Linha de fomento: Auxílio à Pesquisa - Regular