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Unveiling extremely veiled T Tauri stars

Gahm, G. F. and Walter, F. M. and Stempels, H. C. and Petrov, P. P. and Herczeg, G. J. (2008) Unveiling extremely veiled T Tauri stars. Astronomy and Astrophysics, 482 (3). L35-L38. ISSN 0004-6361.

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Context. Photospheric absorption lines in classical T Tauri stars (CTTS) are weak compared to normal stars. This so-called veiling is normally identified with an excess continuous emission formed in shock-heated gas at the stellar surface below the accretion streams. Aims. We have selected four stars (RW Aur A, RU Lup, S CrA NW and S CrA SE) with unusually strong veiling to make a detailed investigation of veiling versus stellar brightness and emission line strengths for comparisons to standard accretion models. Methods. We have monitored the stars photometrically and spectroscopically at several epochs. Results. In standard accretion models a variable accretion rate will lead to a variable excess emission. Consequently, the stellar brightness should vary accordingly. We find that the veiling of absorption lines in these stars is strongly variable and usually so large that it would require the release of several stellar luminosities of potential energy. At states of very large line dilution, the correspondingly large veiling factors derived correlate only weakly with brightness. Moreover, the emission line strengths violate the expected trend of veiling versus line strength. The veiling can change dramatically in one night, and is not correlated with the phase of the rotation periods found for two stars. Conclusions. We show that in at least three of the stars, when the veiling becomes high, the photospheric lines become filled-in by line emission, which produces large veiling factors unrelated to changes in any continuous emission from shocked regions. We also consider to what extent extinction by dust and electron scattering in the accretion stream may affect veiling measures in CTTS. We conclude that the degree of veiling cannot be used as a measure of accretion rates in CTTS with rich emission line spectra.

Item Type:Article
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Herczeg, G. J.0000-0002-7154-6065
Additional Information:© ESO 2008. Received 31 January 2008. Accepted 19 March 2008. This work was supported by the INTAS grant 03-51-6311 and the Swedish National Space Board.
Funding AgencyGrant Number
Swedish National Space Board (SNSB)UNSPECIFIED
Subject Keywords:stars: pre-main sequence; accretion; accretion disks; stars: individual: RW Aur A; stars: variables: general; stars: individual: RU Lup; stars: individual: S CrA
Issue or Number:3
Record Number:CaltechAUTHORS:20090510-183245628
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14188
Deposited By: Joy Painter
Deposited On:13 May 2009 17:38
Last Modified:03 Oct 2019 00:47

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