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Title:
The Differential Rotation of κ1 Ceti as Observed by MOST
Authors:
Walker, Gordon A. H.; Croll, Bryce; Kuschnig, Rainer; Walker, Andrew; Rucinski, Slavek M.; Matthews, Jaymie M.; Guenther, David B.; Moffat, Anthony F. J.; Sasselov, Dimitar; Weiss, Werner W.
Affiliation:
AA(1234 Hewlett Place, Victoria, BC V8S 4P7, Canada; .), AB(Department of Physics and Astronomy, UBC, Vancouver, BC V6T 1Z1, Canada; , , .), AC(Department of Physics and Astronomy, UBC, Vancouver, BC V6T 1Z1, Canada; , , .), AD(Sumus Technology Ltd.; .), AE(Department of Astronomy and Astrophysics, David Dunlap Observatory, University of Toronto, Richmond Hill, ON L4C 4Y6, Canada; .), AF(Department of Physics and Astronomy, UBC, Vancouver, BC V6T 1Z1, Canada; , , .), AG(Department of Astronomy and Physics, St. Mary's University, Halifax, NS B3H 3C3, Canada; .), AH(Department of Physics, University of Montreal, Succursale Centre-Ville, Montreal, QC H3C 3J7; and Mont Megantic Astronomical Observatory, Notre-Dame-des-Bois, PQ J0B 2E0, Canada; .), AI(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138; .), AJ(Institut für Astronomie, Universität Wien, A-1180 Wien, Austria; .)
Publication:
The Astrophysical Journal, Volume 659, Issue 2, pp. 1611-1622. (ApJ Homepage)
Publication Date:
04/2007
Origin:
UCP
ApJ Keywords:
Stars: Activity, stars: individual (κ1 Ceti), stars: individual (HD 20630), Stars: Late-Type, Stars: Oscillations, Stars: Rotation, Stars: Spots
DOI:
10.1086/511851
Bibliographic Code:
2007ApJ...659.1611W

Abstract

We first reported evidence for differential rotation of κ1 Ceti in Paper I. In this paper we demonstrate that the differential rotation pattern closely matches that for the Sun. This result is based on additional MOST observations in 2004 and 2005, as well as those from 2003. Using StarSpotz, a program developed specifically to analyze MOST photometry, we have solved for k, the differential rotation coefficient, and Peq, the equatorial rotation period using the light curves from all three years. The absolute range in spot latitudes is 10°-75° and k=0.090+0.006-0.005, less than the solar value but consistent with the younger age of the star; k is also well constrained by the independent spectroscopic estimate of vsini. We demonstrate independently that the pattern of differential rotation with latitude is indeed solar. Details are given of the parallel tempering formalism used in finding the most robust solution, which gives Peq=8.77+0.03-0.04 days, smaller than that usually adopted, implying an age <750 My. Our values of Peq and k can explain the range of rotation periods others have found by spots or activity at a variety of latitudes. Historically, Ca II activity seems to occur consistently between latitudes 50° and 60°, which might indicate a permanent magnetic feature. Knowledge of k and Peq is key to understanding the dynamo mechanism and rotation structure in the convective zone, as well assessing age for solar-type stars. We recently published values of k and Peq for ɛ Eri based on MOST photometry and expect to analyze MOST light curves for several more spotted, solar-type stars.

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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