A&A 436, 209-230 (2005)
DOI: 10.1051/0004-6361:20042484

[O I] 6300 Å emission in Herbig Ae/Be systems: Signature of Keplerian rotation

B. Acke¹, M. E. van den Ancker² and C. P. Dullemond<sup>3

1</sup>  Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
    e-mail: Bram.Acke@ster.kuleuven.ac.be
²  European Southern Observatory, Karl-Schwarzschild Strasse 2, 85748 Garching bei München, Germany
³  Max-Planck-Institut für Astrophysik, Karl-Schwarzschildstrasse 1, Postfach 1317, 85748 Garching bei München, Germany

(Received 6 December 2004 / Accepted 21 February 2005 )

Abstract
We present high spectral-resolution optical spectra of 49 Herbig Ae/Be stars in a search for the [O I] 6300 Å line. The vast majority of the stars in our sample show narrow (  km s^-1) emission lines, centered on the stellar radial velocity. In only three sources is the feature much broader (~400 km s^-1), and strongly blueshifted (-200 km s^-1) compared to the stellar radial velocity. Some stars in our sample show double-peaked line profiles, with peak-to-peak separations of ~10 km s^-1. The presence and strength of the [O I] line emission appears to be correlated with the far-infrared energy distribution of each source: stars with a strong excess at 60 m have in general stronger [O I] emission than stars with weaker 60 m excesses. We interpret these narrow [O I] 6300 Å line profiles as arising in the surface layers of the protoplanetary disks surrounding Herbig Ae/Be stars. A simple model for [O I] 6300 Å line emission due to the photodissociation of OH molecules shows that our results are in quantitative agreement with that expected from the emission of a flared disk if the fractional OH abundance is ~ .

Key words: circumstellar matter -- stars: pre-main-sequence -- planetary systems: protoplanetary disks

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© ESO 2005

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