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Astron. Astrophys. 341, 553-559 (1999)


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Brightening of the T Tauri star RY Tauri in 1996 * **

Photometry, polarimetry and high-resolution spectroscopy

P.P. Petrov  *** 1, G.V. Zajtseva 2, Yu.S. Efimov 3, R. Duemmler 1, I.V. Ilyin 1, I. Tuominen 1 and V.A. Shcherbakov 3

1 Astronomy Division, University of Oulu, Linnanmaa, P.O. Box 333, FIN-90571 Oulu, Finland
2 Sternberg Astronomical Institution, University pr. 13, 119899 Moscow, Russia
3 Crimean Astrophysical Observatory, p/o Nauchny, 334413 Crimea, Ukraine

Received 7 September 1998 / Accepted 27 October 1998

Abstract

The T Tauri star RY Tau has increased its brightness from V[FORMULA] to V[FORMULA] in October-November 1996. By February-March 1997, the star has faded again to V[FORMULA]. High-resolution échelle spectra of RY Tau were obtained with the SOFIN spectrograph at the Nordic Optical Telescope (La Palma, Spain) at low and high brightness levels of the star. No significant changes in the photospheric lines, which are sensitive to temperature and gravity, were noticed. The spectral type of RY Tau is defined as G1-2 IV, which in combination with photometric data implies [FORMULA]. Polarimetric patrol of RY Tau during the fading of the star showed an increase of its intrinsic polarization from 0.5-1.0% at high brightness to about 2% at low brightness in the V, R and I bands. The flux radiated in H[FORMULA] and the IR Ca ii emission lines remained about the same, in spite of the one magnitude difference in the continuum flux. These results indicate that variable obscuration of the star by circumstellar dust clouds was responsible for the brightness change of RY Tau, and that the emission line source is mostly outside of the obscured region.

Key words: stars: circumstellar matter – stars: individual: RY Tau – stars: pre-main sequence

* based on observations collected at the Nordic Optical Telescope (NOT), European Northern Observatory, La Palma, Spain; at the 2.6m and the 1.25m telescopes of the Crimean Astrophysical Observatory; at the 60cm telescope of the Crimean Laboratory of the Sternberg Astronomical Institution.
** Tables 2 and 3 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr/pub/cats/J/A+A/341/553 (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/341/553
*** on leave from Crimean Astrophysical Observatory

Send offprint requests to: P. Petrov

Correspondence to: Peter.Petrov@Oulu.Fi

© European Southern Observatory (ESO) 1999

Online publication: December 4, 1998

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