A&A 468, 1039-1044 (2007)
DOI: 10.1051/0004-6361:20066793

Rotational period of GQ Lupi

C. Broeg^{1, 2, 3}, T. O. B. Schmidt¹, E. Guenther², A. Gaedke^{4, 1}, A. Bedalov¹, R. Neuhäuser¹, and F. M. Walter<sup>5

1</sup>  Astrophysikalisches Institut und Universitäts-Sternwarte Jena, Schillergäßchen 2-3, 07745 Jena, Germany
    e-mail: broeg@space.unibe.ch
²  Thüringer Landessternwarte, Sternwarte 5, 07778 Tautenburg, Germany
³  Max-Planck Institute for extraterrestrial Physics, Giessenbachstrasse, Garching, 85741, Germany
⁴  Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
⁵  Department of Physics and Astronomy, Stony Brook University, NY 11794-3800, USA

(Received 22 November 2006 / Accepted 20 March 2007)

Abstract
Aims. We wanted to determine the rotation parameters of GQ Lup A, thereby constraining the evolutionary history of the GQ Lup system.
Methods.We have undertaken a photometric monitoring campaign on GQ Lup A consisting of two epochs spaced one year apart. We also searched the photometric archives to enlarge the data set.
Results.We were able to determine the photometric period ( days) in both epochs in several photometric bands. This periodicity could also be found in some of the archival data. The combined false-alarm probability is 0.015. The variation is most likely caused by hot spots on the surface of GQ Lup A. This, combined with high-resolution spectra () allows calculation of GQ Lup A's inclination ( ). Radial velocity data also contains this period but is inconclusive. Nevertheless, the RV data supports the interpretation that hot spots cause the photometric variation. We use the known K-band variability, amplitude, and phase of GQ Lup A together with a new image of GQ Lup A+b, taken quasi-simultaneously with our monitoring of the star, to confirm the magnitude and, hence, luminosity of the companion.

Key words: stars: rotation -- stars: fundamental parameters -- stars: starspots

© ESO 2007

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