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MOST Spacebased Photometry of HD 189733: Precise Timing Measurements for Transits Across an Active Star

Published online by Cambridge University Press:  01 May 2008

E. Miller-Ricci
Affiliation:
Harvard Smithsonian Center for Astrophysics60 Garden St., Cambridge, MA 02138 email: emillerricci@cfa.harvard.edu
J. F. Rowe
Affiliation:
NASA-Ames Research Park, MS-244-30, Moffett Field, CA 94035-1000 email: jasonfrowe@gmail.com
D. Sasselov
Affiliation:
Harvard Smithsonian Center for Astrophysics60 Garden St., Cambridge, MA 02138 email: emillerricci@cfa.harvard.edu
J. M. Matthews
Affiliation:
Department of Physics and Astronomy, University of British Columbia6224 Agricultural Rd., Vancouver, BC V6T 1Z1, Canada
R. Kuschnig
Affiliation:
Institut für Astronomie, Universität Wien Türkenschanzstrasse 17, A-1180 Wien, Austria
B. Croll
Affiliation:
Department of Astronomy and Astrophysics, University of Toronto50 Saint George St., Toronto, ON M5S 3H4, Canada
D. B. Guenther
Affiliation:
Department of Astronomy and Physics, St. Mary's UniversityHalifax, NS B3H 3C3, Canada
A. F. J. Moffat
Affiliation:
Département de Physique, Université de MontréalC.P. 6128, Succ. Centre-Ville, Montréal, QC H3C 3J7, Canada
S. Rucinski
Affiliation:
Department of Astronomy and Astrophysics, University of Toronto50 Saint George St., Toronto, ON M5S 3H4, Canada
G. A. H Walker
Affiliation:
Department of Physics and Astronomy, University of British Columbia6224 Agricultural Rd., Vancouver, BC V6T 1Z1, Canada
W. W. Weiss
Affiliation:
Institut für Astronomie, Universität Wien Türkenschanzstrasse 17, A-1180 Wien, Austria
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Abstract

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We have measured transit times for HD 189733 passing in front of its bright (V = 7.67) chromospherically active and spotted parent star. Nearly continuous broadband photometry of this system was obtained with the MOST (Microvariability & Oscillations of STars) space telesope during 21 days in August 2006, monitoring 10 consecutive transits. We have used these data to search for deviations from a constant orbital period which can indicate the presence of additional planets in the system that are as yet undetected by Doppler searches. We find no variations above the level of ±45 s, ruling out planets in the Earth-to-Neptune mass range in a number of resonant orbits. We find that a number of complications can arise in measuring transit times for a planet transiting an active star with large star spots. However, such transiting systems are also useful in that they can help to constrain and test spot models. This has implications for the large number of transiting systems expected to be discovered by the CoRoT and Kepler missions.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2009