An active binary XY UMa revisited

T. Pribulla; D. Chochol; P. A. Heckert; L. Errico; A. A. Vittone; Š. Parimucha; M. Teodorani

doi:doi:10.1051/0004-6361:20010459

Free access

Issue		A&A Volume 371, Number 3, June I 2001


Page(s)		997 - 1011
Section		Formation, structure and evolution of stars
DOI		http://dx.doi.org/10.1051/0004-6361:20010459

A&A 371, 997-1011 (2001)
DOI: 10.1051/0004-6361:20010459

An active binary XY UMa revisited

T. Pribulla¹, D. Chochol¹, P. A. Heckert², L. Errico³, A. A. Vittone³, S. Parimucha¹ and M. Teodorani³

¹ Astronomical Institute of the Slovak Academy of Sciences, 059 60 Tatranská Lomnica, Slovakia
² Department of Chem. & Physics, Western Carolina University, Cullowhee, NC 28723, USA
³ Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131, Napoli, Italy

(Received 18 December 2000 / Accepted 15 March 2001)

Abstract
New extensive multicolour photoelectric photometry, performed since 1994, is presented. 17 more-or-less complete light curves were obtained and analyzed. The Wilson-Devinney code applied to the BVRI light curves without the maculation effect together with published spectroscopic mass ratio and semi-major axis yielded new absolute parameters of the eclipsing pair: $m_1 = 1.10 M_{\odot}$ , $m_2 = 0.66 M_{\odot}$ , $R_1 = 1.16 R_{\odot}$ , $R_2 = 0.63 R_{\odot}$ , $a = 3.107 R_{\odot}$ and the orbital inclination $i = 80.9\degr$ . The observed orbital period changes are conclusively explained by the mutual action of the third body in the system (P₃ = 30 years) and the maculation effects. Simultaneous analysis of the period changes and the visual brightness excludes the possibility of their explanation by Applegate's mechanism. The differences in the maxima heights caused by the maculation exhibit variations with the period of $709 \pm 10$ days. The distance to the system $d = 86 \pm 5$ pc determined from the absolute dimensions and luminosities of the components is larger than the Hipparcos astrometric value $d = 66 \pm 6$ pc.

Key words: stars: binaries eclipsing -- stars: individual: XY UMa -- stars: pre-main sequence -- stars: magnetic fields

Offprint request: T. Pribulla, pribulla@ta3.sk

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