An independent analysis of Kepler-4b through Kepler-8b

David Kipping, Gáspár Bakos

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We present two independent, homogeneous, global analyses of the transit light curves, radial velocities, and spectroscopy of Kepler-4b, Kepler-5b, Kepler-6b, Kepler-7b, and Kepler-8b with numerous differences compared to the previous methods. These include: (1) improved decorrelated parameter fitting set used, (2) new limb-darkening coefficients, (3) time stamps modified to barycentric Julian date for consistency with radial velocity data, (4) two different methods for compensating for the long integration time of Kepler long-cadence data, (5) best-fit secondary eclipse depths and excluded upper limits, and (6) fitted mid-transit times, durations, depths, and baseline fluxes for individual transits. We make several determinations not found in the discovery papers. (1) We detect a secondary eclipse for Kepler-7b of depth (47 14)ppm and statistical significance 3.5σ. We conclude that reflected light is a much more plausible origin than thermal emission and determine a geometric albedo of Ag = (0.38 ± 0.12). (2) We find that an eccentric orbit model for the Neptune-mass planet Kepler-4b is detected at the 2σ level with e = (0.25 ± 0.12). If confirmed, this would place Kepler-4b in a similar category as GJ 436b and HAT-P-11b, as an eccentric, Neptune-mass planet. (3) We find weak evidence for a secondary eclipse in Kepler-5b of 2σ significance and depth (26 ± 17)ppm. The most plausible explanation is reflected light caused by a planet of geometric albedo A g = (0.15 ± 0.10). (4) A 2.6σ peak in Kepler-6b TTV periodogram is detected and is not easily explained as an aliased frequency. We find that mean-motion resonant (MMR) perturbers, non-resonant perturbers, and a companion extrasolar moon all provide inadequate explanations for this signal and the most likely source is stellar rotation. (5) We find different impact parameters relative to the discovery papers in most cases, but generally self-consistent when compared to the two methods employed here. (6) We constrain the presence of MMR planets for all five planets through an analysis of the mid-transit times. (7) We constrain the presence of extrasolar moons for all five planets. (8) We constrain the presence of Trojans for all five planets.

Original languageEnglish (US)
Article number50
JournalAstrophysical Journal
Issue number1
StatePublished - Mar 20 2011
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • planetary systems
  • stars: individual (Kepler-4, Kepler-5, Kepler-6, Kepler-7, Kepler-8)
  • techniques: photometric
  • techniques: spectroscopic


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