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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
The absence of sub-minute periodicity in classical T Tauri stars
Astronomy and Astrophysics, Volume 518, No. 19, Article A54, Year 2010
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Description
Context. Classical T Tauri stars (CTTS) are young, late-type objects, that still accrete matter from a circumstellar disk. Analytical treatments and numerical simulations predict instabilities of the accretion shock on the stellar surface. Aims. We search for variability on timescales below a few minutes in the CTTS TW Hya and AA Tau. Methods. TW Hya was observed with SALTICAM on the Southern African Large Telescope (SALT) in narrow-band filters around the Balmer jump. The observations were performed in slit mode, which provides a time resolution of about 0.1 s. For AA Tau we obtained observations with OPTIMA, a single photon-counting device with even better time resolution. Results. Small-scale variability typically lasts a few seconds, however, no significant periodicity is detected. We place a 99% confidence upper limit on the pulsed fraction of the lightcurves. The relative amplitude is below 0.001 for TW Hya in the frequency range 0.02-3 Hz in the 340 nm filter and 0.1-3 Hz in the 380 nm filter. The corresponding value for AA Tau is an amplitude of 0.005 for 0.02-50 Hz. Conclusions. The relevant timescales indicate that shock instabilites should not be seen directly in our optical and UV observations, but the predicted oscialltions would induce observable variations in the reddening. We discuss how the magnetic field could stabilise the accretion shock. © 2010 ESO.
Authors & Co-Authors
Günther, H. Moritz
Germany, Hamburg
Universität Hamburg
Lewandowska, Natalia
Germany, Hamburg
Universität Hamburg
Hundertmark, Markus P.G.
Germany, Gottingen
Georg-august-universität Göttingen
Steinle, Helmut
Germany, Garching Bei Munchen
Max Planck Institute for Extraterrestrial Physics
Schmitt, J. H.M.M.
Germany, Hamburg
Universität Hamburg
Buckley, David A.H.
South Africa, Cape Town
South African Astronomical Observatory
Crawford, Steven M.
South Africa, Cape Town
South African Astronomical Observatory
O'Donoghue, Darragh E.
South Africa, Cape Town
South African Astronomical Observatory
Väisänen, Petri S.M.
South Africa, Cape Town
South African Astronomical Observatory
Statistics
Citations: 23
Authors: 9
Affiliations: 4
Identifiers
Doi:
10.1051/0004-6361/201013996
ISSN:
00046361
e-ISSN:
14320746