Modeling Kepler transit light curves as false positives: Rejection of blend scenarios for Kepler-9, and validation of Kepler-9 d, a super-earth-size planet in a multiple system

Guillermo Torres, François Fressin, Natalie M. Batalha, William J. Borucki, Timothy M. Brown, Stephen T. Bryson, Lars A. Buchhave, David Charbonneau, David R. Ciardi, Edward W. Dunham, Daniel C. Fabrycky, Eric B. Ford, Thomas N. Gautier, Ronald L. Gilliland, Matthew J. Holman, Steve B. Howell, Howard Isaacson, Jon M. Jenkins, David G. Koch, David W. LathamJack J. Lissauer, Geoffrey W. Marcy, David G. Monet, Andrej Prsa, Samuel N. Quinn, Darin Ragozzine, Jason F. Rowe, Dimitar D. Sasselov, Jason H. Steffen, William F. Welsh

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Abstract

Light curves from the Kepler Mission contain valuable information on the nature of the phenomena producing the transit-like signals. To assist in exploring the possibility that they are due to an astrophysical false positive, we describe a procedure (BLENDER) to model the photometry in terms of a "blend" rather than a planet orbiting a star. A blend may consist of a background or foreground eclipsing binary (or star-planet pair) whose eclipses are attenuated by the light of the candidate and possibly other stars within the photometric aperture. We apply BLENDER to the case of Kepler-9 (KIC 3323887), a target harboring two previously confirmed Saturn-size planets (Kepler-9 b and Kepler-9 c) showing transit timing variations, and an additional shallower signal with a 1.59 day period suggesting the presence of a super-Earth-size planet. Using BLENDER together with constraints from other follow-up observations we are able to rule out all blends for the two deeper signals and provide independent validation of their planetary nature. For the shallower signal, we rule out a large fraction of the false positives that might mimic the transits. The false alarm rate for remaining blends depends in part (and inversely) on the unknown frequency of small-size planets. Based on several realistic estimates of this frequency, we conclude with very high confidence that this small signal is due to a super-Earth-size planet (Kepler-9 d) in a multiple system, rather than a false positive. The radius is determined to be 1.64+0.19-0.14 R., and current spectroscopic observations are as yet insufficient to establish its mass.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume727
Issue number1
DOIs
StatePublished - Jan 20 2011

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All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Torres, G., Fressin, F., Batalha, N. M., Borucki, W. J., Brown, T. M., Bryson, S. T., Buchhave, L. A., Charbonneau, D., Ciardi, D. R., Dunham, E. W., Fabrycky, D. C., Ford, E. B., Gautier, T. N., Gilliland, R. L., Holman, M. J., Howell, S. B., Isaacson, H., Jenkins, J. M., Koch, D. G., ... Welsh, W. F. (2011). Modeling Kepler transit light curves as false positives: Rejection of blend scenarios for Kepler-9, and validation of Kepler-9 d, a super-earth-size planet in a multiple system. Astrophysical Journal, 727(1). https://doi.org/10.1088/0004-637X/727/1/24