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Time Variation of Kepler Transits Induced by Stellar Spots—A Way to Distinguish between Prograde and Retrograde Motion. II. Application to KOIs

Holczer, Tomer and Shporer, Avi and Mazeh, Tsevi and Fabrycky, Daniel and Nachmani, Gil and McQuillan, Amy and Sanchis-Ojeda, Roberto and Orosz, Jerome A. and Welsh, WIlliam F. and Ford, Eric B. and Jontof-Hutter, Daniel (2015) Time Variation of Kepler Transits Induced by Stellar Spots—A Way to Distinguish between Prograde and Retrograde Motion. II. Application to KOIs. Astrophysical Journal, 807 (2). Art. No. 170. ISSN 0004-637X.

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Mazeh et al. have presented an approach that can, in principle, use the derived transit timing variation (TTV) of some transiting planets observed by the Kepler mission to distinguish between the prograde and retrograde motion of their orbits with respect to their parent stars' rotation. The approach utilizes TTVs induced by spot-crossing events that occur when the planet moves across a spot on the stellar surface, looking for a correlation between the derived TTVs and the stellar brightness derivatives at the corresponding transits. This can work even in data that cannot temporally resolve the spot-crossing events themselves. Here, we apply this approach to the Kepler KOIs, identifying nine systems where the photometric spot modulation is large enough and the transit timing accurate enough to allow detection of a TTV-brightness-derivatives correlation. Of those systems, five show highly significant prograde motion (Kepler-17b, Kepler-71b, KOI-883.01, KOI-895.01, and KOI-1074.01), while no system displays retrograde motion, consistent with the suggestion that planets orbiting cool stars have prograde motion. All five systems have impact parameter 0.2≲b≲0.5, and all systems within that impact parameter range show significant correlation, except HAT-P-11b where the lack of a correlation follows its large stellar obliquity. Our search suffers from an observational bias against detection of high impact parameter cases, and the detected sample is extremely small. Nevertheless, our findings may suggest that stellar spots, or at least the larger ones, tend to be located at low stellar latitude, but not along the stellar equator, similar to the Sun.

Item Type:Article
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URLURL TypeDescription Paper
Shporer, Avi0000-0002-1836-3120
Fabrycky, Daniel0000-0003-3750-0183
Additional Information:© 2015 The American Astronomical Society. Received 2015 April 14; accepted 2015 May 29; published 2015 July 9. We wish to warmly thank Jason Rowe, Fergal Mullally, and Jack Lissauer, for discussions and feedback that helped improve this paper. The research leading to these results has received funding from the European Research Council under the EU's Seventh Framework Programme (FP7/(2007-2013)/ ERC Grant Agreement No. 291352). T.M. acknowledges support from the Israel Science Foundation (grant No. 1423/11) and the Israeli Centers of Research Excellence (I-CORE, grant No. 1829/12). E. B. F. was supported in part by NASA Kepler Participating Scientist Program award NNX12AF73G, NASA Origins of Solar Systems award NNX14AI76G, and NASA Exoplanet Research Program award NNX15AE21G. The Center for Exoplanets and Habitable Worlds is supported by the Pennsylvania State University, the Eberly College of Science, and the Pennsylvania Space Grant Consortium. W.F.W. and J.A.O. gratefully acknowledge support from the NSF via grant AST-1109928, and from NASA via grants NNX13AI76G-3 and NNX14AB91G. D.F. was supported by the National Aeronautics and Space Administration under Grant No. NNX14AB87G issued through the Kepler Participating Scientists Program. The last phase of this study was done when T.M. and R.S. were members of the KITP program of "Dynamics and Evolution of earth-like Planets." They wish to thank the director of KITP, Lars Bidsten, and the coordinators of the program, Eric Ford, Louise Kellogg, Geoff Marcy, and Burkhard Militzer, for participation in the program. This work was performed in part at the Jet Propulsion Laboratory, under contract with the California Institute of Technology (Caltech) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. All photometric data presented in this paper were obtained from the Mikulsky Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts.
Funding AgencyGrant Number
European Research Council (ERC)291352
Israel Science Foundation1423/11
Israel Science Foundation1829/12
Subject Keywords:planetary systems; stars: activity; stars: rotation; techniques: photometric
Issue or Number:2
Record Number:CaltechAUTHORS:20150827-122003217
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Official Citation:Time Variation of Kepler Transits Induced by Stellar Spots—A Way to Distinguish between Prograde and Retrograde Motion. II. Application to KOIs Tomer Holczer et al. 2015 ApJ 807 170
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59930
Deposited By: Jason Perez
Deposited On:27 Aug 2015 22:26
Last Modified:03 Oct 2019 08:51

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