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Title: Hubble space telescope near-ir transmission spectroscopy of the super-Earth HD 97658B

Recent results from the Kepler mission indicate that super-Earths (planets with masses between 1-10 times that of the Earth) are the most common kind of planet around nearby Sun-like stars. These planets have no direct solar system analogue, and are currently one of the least well-understood classes of extrasolar planets. Many super-Earths have average densities that are consistent with a broad range of bulk compositions, including both water-dominated worlds and rocky planets covered by a thick hydrogen and helium atmosphere. Measurements of the transmission spectra of these planets offer the opportunity to resolve this degeneracy by directly constraining the scale heights and corresponding mean molecular weights of their atmospheres. We present Hubble Space Telescope near-infrared spectroscopy of two transits of the newly discovered transiting super-Earth HD 97658b. We use the Wide Field Camera 3's (WFC3) scanning mode to measure the wavelength-dependent transit depth in 30 individual bandpasses. Our averaged differential transmission spectrum has a median 1σ uncertainty of 23 ppm in individual bins, making this the most precise observation of an exoplanetary transmission spectrum obtained with WFC3 to date. Our data are inconsistent with a cloud-free solar metallicity atmosphere at the 10σ level. They are consistent at the 0.4σ levelmore » with a flat line model, as well as effectively flat models corresponding to a metal-rich atmosphere or a solar metallicity atmosphere with a cloud or haze layer located at pressures of 10 mbar or higher.« less
Authors:
 [1] ;  [2] ; ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9]
  1. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States)
  2. Las Cumbres Observatory Global Telescope Network, Goleta, CA 93117 (United States)
  3. Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States)
  4. Department of Physics, Grinnell College, Grinnell, IA 50112 (United States)
  5. Space Telescope Science Institute, Baltimore, MD 21218 (United States)
  6. Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
  7. Institut d'Astrophysique et de Géophysique, Universiteé de Liége, Liége 1 (Belgium)
  8. Centre de Recherche Astrophysique de Lyon, F-69364 Lyon (France)
  9. Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States)
Publication Date:
OSTI Identifier:
22370389
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 794; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION SPECTROSCOPY; ATMOSPHERES; DENSITY; EARTH PLANET; GLOBAL ASPECTS; HELIUM; HYDROGEN; INFRARED SPECTRA; MASS; METALLICITY; METALS; MOLECULAR WEIGHT; SCALE HEIGHT; SOLAR SYSTEM; SPACE; SUN; TELESCOPES; TRANSMISSION; WATER; WAVELENGTHS