Volume 379, Number 2, November IV 2001
|Page(s)||564 - 578|
|Section||Interstellar and circumstellar matter|
|Published online||15 November 2001|
EXPORT: Optical photometry and polarimetry of Vega-type and pre-main sequence stars*
The Department of Physics and Astronomy, E C Stoner Building, Leeds, LS2 9JT, UK
2 Dpto. Física Teórica, C-XI, Facultad de Ciencias, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
3 Joint Astronomy Centre, 660 N. A'ohoku Place, Hilo, Hawaii 96720, USA
4 TNO/TPD-Space Instrumentation, Stieltjesweg 1, PO Box 155, 2600 AD Delft, The Netherlands
5 CNRS, Institut d'Astrophysique de Paris, 98bis Bld. Arago, 75014 Paris, France
6 Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
7 NOAO/STIS, Goddard Space Flight Center, Code 681, NASA/GSFC, Greenbelt, MD 20771, USA
8 Physics & Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS, Scotland, UK
9 Instituto de Astrofísica de Andalucía, Apartado de Correos 3004, 18080 Granada, Spain
10 DLR Institute of Space Sensor Technology and Planetary Exploration, Rutherfordstrasse 2, 12489 Berlin, Germany
11 LAEFF, VILSPA, Apartado de Correos 50727, 28080 Madrid, Spain
12 Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, UK
13 Department of Physics, Center for Astrophysics and Space Sciences, University of California San Diego, Mail Code 0424, La Jolla, CA 92093-0424, USA
14 Observatoire de Paris, 92195 Meudon, France
15 SRON, Universiteitscomplex "Zernike", Landleven 12, PO Box 800, 9700 AV Groningen, The Netherlands
Corresponding author: R. D. Oudmaijer, firstname.lastname@example.org
Accepted: 20 September 2001
This paper presents optical UBVRI broadband photo-polarimetry of the EXPORT sample obtained at the 2.5 m Nordic Optical Telescope. The database consists of multi-epoch photo-polarimetry of 68 pre-main-sequence and main-sequence stars. An investigation of the polarization variability indicates that 22 objects are variable at the 3σ level in our data. All these objects are pre-main sequence stars, consisting of both T Tauri and Herbig Ae/Be objects while the main sequence, Vega type and post-T Tauri type objects are not variable. The polarization properties of the variable sources are mostly indicative of the UXOR-type behaviour; the objects show highest polarization when the brightness is at minimum. We add seven new objects to the class of UXOR variables (BH Cep, VX Cas, DK Tau, HK Ori, LkHα 234, KK Oph and RY Ori). The main reason for their discovery is the fact that our data-set is the largest in its kind, indicating that many more young UXOR-type pre-main sequence stars remain to be discovered. The set of Vega-like systems has been investigated for the presence of intrinsic polarization. As they lack variability, this was done using indirect methods, and apart from the known case of BD+31o643, the following stars were found to be strong candidates to exhibit polarization due to the presence of circumstellar disks: 51 Oph, BD+31o643C, HD 58647 and HD 233517.
Key words: techniques: photometric / techniques: polarimetric / stars: circumstellar matter / stars: pre-main sequence / stars: variables: general
© ESO, 2001
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