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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.)

Beyond the diffraction limit of optical/IR interferometers I. Angular diameter and rotation parameters of Achernar from differential phases

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Autor(es):
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de Souza, A. Domiciano [1] ; Hadjara, M. [1, 2] ; Vakili, F. [1] ; Bendjoya, P. [1] ; Millour, F. [1] ; Abe, L. [1] ; Carciofi, A. C. [3] ; Faes, D. M. [3, 1] ; Kervella, P. [4] ; Lagarde, S. [1] ; Marconi, A. [5] ; Monin, J. -L. [6] ; Niccolini, G. [1] ; Petrov, R. G. [1] ; Weigelt, G. [7]
Número total de Autores: 15
Afiliação do(s) autor(es):
[1] Univ Nice Sophia Antipolis UNS, Lab JL Lagrange, CNRS, UMR 7293, OCA, F-06108 Nice 2 - France
[2] CRAAG, Bouzareah 16340, Alger - Algeria
[3] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508900 Sao Paulo - Brazil
[4] Univ Paris Diderot, Observ Paris, CNRS UMR 8109, LESIA, UPMC, F-92195 Meudon - France
[5] Osserv Astrofis Arcetri, INAF, I-50125 Florence - Italy
[6] UJF Grenoble 1, Inst Planetol & Astrophys Grenoble IPAG UMR 5274, CNRS, INSU, F-38041 Grenoble - France
[7] Max Planck Inst Radioastron, D-53121 Bonn - Germany
Número total de Afiliações: 7
Tipo de documento: Artigo Científico
Fonte: Astronomy & Astrophysics; v. 545, SEP 2012.
Citações Web of Science: 20
Resumo

Context. Spectrally resolved long-baseline optical/IR interferometry of rotating stars opens perspectives to investigate their fundamental parameters and the physical mechanisms that govern their interior, photosphere, and circumstellar envelope structures. Aims. Based on the signatures of stellar rotation on observed interferometric wavelength-differential phases, we aim to measure angular diameters, rotation velocities, and orientation of stellar rotation axes. Methods. We used the AMBER focal instrument at ESO-VLTI in its high-spectral resolution mode to record interferometric data on the fast rotator Achernar. Differential phases centered on the hydrogen Br gamma line (K band) were obtained during four almost consecutive nights with a continuous Earth-rotation synthesis during similar to 5h/night, corresponding to similar to 60 degrees position angle coverage per baseline. These observations were interpreted with our numerical code dedicated to long-baseline interferometry of rotating stars. Results. By fitting our model to Achernar's differential phases from AMBER, we could measure its equatorial radius R-eq = 11.6 +/- 0.3 R-circle dot, equatorial rotation velocity V-eq = 298 +/- 9 km s(-1), rotation axis inclination angle i = 101.5 +/- 5.2 degrees, and rotation axis position angle (from North to East) PA(rot) = 34.9 +/- 1.6 degrees. From these parameters and the stellar distance, the equatorial angular diameter circle divide(eq) of Achernar is found to be 2.45 +/- 0.09 mas, which is compatible with previous values derived from the commonly used visibility amplitude. In particular, circle divide(eq) and PA(rot) measured in this work with VLTI/AMBER are compatible with the values previously obtained with VLTI/VINCI. Conclusions. The present paper, based on real data, demonstrates the super-resolution potential of differential interferometry for measuring sizes, rotation velocities, and orientation of rotating stars in cases where visibility amplitudes are unavailable and/or when the star is partially or poorly resolved. In particular, we showed that differential phases allow the measurement of sizes up to similar to 4 times smaller than the diffraction-limited angular resolution of the interferometer. (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