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Title:
Differential Rotation of ɛ Eridani Detected by MOST
Authors:
Croll, Bryce; Walker, Gordon A. H.; Kuschnig, Rainer; Matthews, Jaymie M.; Rowe, Jason F.; Walker, Andrew; Rucinski, Slavek M.; Hatzes, Artie P.; Cochran, William D.; Robb, Russell M.; Guenther, David B.; Moffat, Anthony F. J.; Sasselov, Dimitar; Weiss, Werner W.
Affiliation:
AA(Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada; , , , .), AB(1234 Hewlett Place, Victoria, BC V8S 4P7, Canada; .), AC(Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada; , , , .), AD(Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada; , , , .), AE(Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada; , , , .), AF(Sumus Technology Limited, Vancouver, BC, Canada; .), AG(Department of Astronomy and Astrophysics, David Dunlap Observatory, University of Toronto, P.O. Box 360, Richmond Hill, ON L4C 4Y6, Canada; .), AH(Thüringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg, Germany; .), AI(McDonald Observatory, University of Texas, Austin, TX 78712; .), AJ(Department of Physics and Astronomy, P.O. Box 3055, University of Victoria, BC V8W 3P6, Canada; .), AK(Department of Astronomy and Physics, St. Mary's University, Halifax, NS B3H 3C3, Canada; .), AL(Département de physique, Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal, QC H3C 3J7, and Observatoire du mont Mégantic, Canada; .), AM(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138; .), AN(Institut für Astronomie, Universität Wien Türkenschanzstrasse 17, A-1180 Wien, Austria; .)
Publication:
The Astrophysical Journal, Volume 648, Issue 1, pp. 607-613. (ApJ Homepage)
Publication Date:
09/2006
Origin:
UCP
ApJ Keywords:
Stars: Planetary Systems, Stars: Activity, stars: individual (ɛ Eri), Stars: Late-Type, Stars: Rotation, Stars: Spots
DOI:
10.1086/505792
Bibliographic Code:
2006ApJ...648..607C

Abstract

The Microvariability and Oscillations of STars (MOST) photometric satellite observed three rotations of ɛ Eri continuously in late 2005. We detected two spots (Δm~0.01) at different latitudes (20.0d, 31.5d) revolving with different periods (11.35 days, 11.55 days), from which we derive a differential rotation coefficient, k=0.11+.03-.02, in agreement with the prediction by Brown and coworkers for a young Sun-like star having roughly twice the solar angular velocity. The light curve was analyzed with the program StarSpotz, a modification of SPOTMODEL by Ribárik and coworkers. The best-fitting value for the inclination angle i=30deg+/-3deg is compatible with inclinations already estimated for the disk (~25°) and planetary orbit (26.2d). The inclination also leads to an equatorial rotation speed of 3.42 km s-1 and the photometric value of vsini=1.7 km s-1. When compared with spectroscopically determined values, the photometric vsini allows, in principle, an independent estimate of the macroturbulent velocity. Both spots would have distorted the radial velocity curve ~+/-10 m s-1 by the Rossiter-McLaughlin effect, which is similar to the stellar radial velocity ``noise'' detected by others. Details of the StarSpotz model and of the uniqueness tests that we applied in order to arrive at a best solution and realistic estimates of errors in the derived parameters are given.

Based on data from the MOST satellite, a Canadian Space Agency mission, jointly operated by Dynacon Inc., the University of Toronto Institute of Aerospace Studies, and the University of British Columbia, with the assistance of the University of Vienna.


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