Poster Abstracts - Kepler - NASA

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POSTER ABSTRACTSP0709. POSTER SESSION IIDIFFERENTIAL ROTATION IN KEPLER OPEN CLUSTER STARS.S. H. Saar 1 and S Meibom 1 ,1 SAO 60 Garden Street Cambridge, MA 02138 saar@cfa.harvard.edu;smeibom@cfa.harvard.eduStarspots are regions of magnetic flux on cool starsthat is so concentrated convective heat transport is locallysuppressed. The precision and cadence of Keplermake it a superb instrument for studying the rotationand temporal/spatial evolution of starspots. Analysis ofthese starspot properties can yield important informationon how the magnetic dynamo that generates themactually operates. Open clusters are ideal laboratoriesfor stellar studies since they comprise stars of roughlyfixed age and metallicity. We report on our observationsof spots on cool stars in two open clusters in theKepler field; NGC 6811 (age ~1 Gyr) and NGC 6819(age ~2.5 Gyr). Rotation, differential rotation, andspot growth/decay are all clearly seen by eye in thedata, but other sources of variablility introduce someconfusion. We use a principle components analysisPDC MAP to remove non-intrinsic variability in oursources, and then apply a number of methods (periodogram,gapped wavelet, and modeling) to measuredifferential rotation and growth/decay timscales for theobserved spots. We present our first results, and compareour measurements with other stellar propertiesand previous results.1922011 Kepler Science Conference - NASA Ames Research Center
Stellar Variability From DASCH vs. Kepler DataSumin Tang * , Jonathan Grindlay and Soren MeibomHarvard-Smithsonian Center for Astrophysics, 60 Garden Street, MA 02138* stang@cfa.harvard.eduPOSTER ABSTRACTSP0710. POSTER SESSION IIDASCH (Digital Access to a Sky Century@Harvard)has similar magnitude rangeto Kepler, and therefore Kepler targets arealso covered by DASCH over 100 years.Combining the long-term variations fromDASCH, and the short-term variations fromKepler of great accuracy, enables a uniquestudy of stellar variability on the widest rangeof timescale. Here we present our study of agroup of peculiar long-term K giant variableswith slow variations over decades. Most ofthem show strong star spots and flaring activitiesin the Kepler light curves, which suggeststhat the mysterious long-term variations maybe related to strong star spots and magneticactivities which may be a new mechanism fordust formation or ejection. Preliminary studyof a few other unusual variables are also presented.Figure 2: Kepler light curve of 5095511.Figure 3: Kepler light curve of 5630212.Figure 4: Kepler light curve of 7869590.Figure 1: DASCH light curves of 5 long-termK giant variables in the Kepler FOV.This work was supported in part by NSFgrants AST-0407380 and AST-0909073 andnow also the Cornel and Cynthia K.SarosdyFund for DASCH.2011 Kepler Science Conference - NASA Ames Research Center 193
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Poster Abstracts - Kepler - NASA

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