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Astron. Astrophys. 338, 1015-1030 (1998)

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The [FORMULA] Pictoris circumstellar disk

XXV. The Ca II absorption lines and the Falling Evaporating Bodies model revisited using UHRF observations *

H. Beust 1, A.-M. Lagrange 1, 2, I.A. Crawford 3, C. Goudard , J. Spyromilio 4 and A. Vidal-Madjar 2

1 Laboratoire d'Astrophysique de l'Observatoire de Grenoble, Université J. Fourier, B.P. 53, F-38041 Grenoble Cedex 9, France
2 Institut d'Astrophysique de Paris, CNRS, 98 bis boulevard Arago, F-75014 Paris, France
3 Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
4 E.S.O., Karl-Schwarzschild-Strasse 2, D-8046 Garching bei München, Germany

Received 26 February 1998 / Accepted 3 July 1998

Abstract

We present here ultra high resolution observations of the Ca II K and H lines towards [FORMULA] Pictoris recorded over a period of 3 years and a smaller set of calcium triplet data.

At the present resolution, the central Ca II circumstellar absorption is complex, with several variable components, some of them at very low velocity shifts ([FORMULA]km s-1) with respect to the star, in addition to a very narrow stable component. The stable component is analyzed and physical informations are derived. The variable components at low redshifts are analyzed, and well modeled in the framework of the Falling Evaporating Bodies (FEB) scenario previously invoked to explain the absorption features observed at higher redshifts.

We show that the very low redshift events are well simulated by FEBs crossing the line of sight at somewhat larger distances from the star than those responsible for the higher velocity redshift events. The implications of these new observations on the dynamical process responsible for the FEB phenomenon are discussed. In particular, they put strong constraints on the orbital parameters of the incoming bodies that appear in fact in perfect agreement with an origin based on mean-motion resonances with a massive planet.

Key words: comets: general – stars: circumstellar matter – stars: individual: Beta Pic

* Based on observations collected with the Ultra-High-Resolution Facility (UHRF) at the Anglo-Australian Telescope

Send offprint requests to: H. Beust
Correspondence to: beust@obs.ujf-grenoble.fr

© European Southern Observatory (ESO) 1998

Online publication: September 17, 1998

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