A Lack of Planets in 47 Tucanae from an HST Search
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A Lack of Planets in 47 Tucanae from an HST Search

  • Author(s): Gilliland, Ronald L
  • Brown, TM
  • Guhathakurta, P
  • Sarajedini, A
  • Milone, EF
  • Albrow, MD
  • Baliber, NR
  • Bruntt, H
  • Burrows, A
  • Charbonneau, D
  • Choi, P
  • Cochran, WD
  • Edmonds, PD
  • Frandsen, S
  • Howell, JH
  • Lin, DNC
  • Marcy, GW
  • Mayor, M
  • Naef, D
  • Sigurdsson, S
  • Stagg, CR
  • VandenBerg, DA
  • Vogt, SS
  • Williams, MD
  • et al.
Abstract

We report results from a large Hubble Space Telescope project to observe a significant (~34,000) ensemble of main sequence stars in the globular cluster 47 Tucanae with a goal of defining the frequency of inner-orbit, gas-giant planets. Simulations based on the characteristics of the 8.3 days of time-series data in the F555W and F814W WFPC2 filters show that ~17 planets should be detected by photometric transit signals if the frequency of hot Jupiters found in the solar neighborhood is assumed to hold for 47 Tuc. The experiment provided high-quality data sufficient to detect planets. A full analysis of these WFPC2 data reveals ~75 variables, but NO light curves resulted for which a convincing interpretation as a planet could be made. The planet frequency in 47 Tuc is at least an order of magnitude below that for the solar neighborhood. The cause of the absence of close-in planets in 47 Tuc is not yet known; presumably the low metallicity and/or crowding of 47 Tuc interfered with planet formation, with orbital evolution to close-in positions, or with planet survival.

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