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Title: Deep thermal infrared imaging of HR 8799 bcde: new atmospheric constraints and limits on a fifth planet

We present new L' (3.8 μm) and Brα (4.05 μm) data and reprocessed archival L' data for the young, planet-hosting star HR 8799 obtained with Keck/NIRC2, VLT/NaCo, and Subaru/IRCS. We detect all four HR 8799 planets in each data set at a moderate to high signal-to-noise ratio (S/N ≳ 6-15). We fail to identify a fifth planet, 'HR 8799 f', at r < 15 AU at a 5σ confidence level: one suggestive, marginally significant residual at 0.''2 is most likely a point-spread function artifact. Assuming companion ages of 30 Myr and the Baraffe planet cooling models, we rule out an HR 8799 f with a mass of 5 M{sub J} (7 M{sub J} ), 7 M{sub J} (10 M{sub J} ), or 12 M{sub J} (13 M{sub J} ) at r {sub proj} ∼ 12 AU, 9 AU, and 5 AU, respectively. All four HR 8799 planets have red early T dwarf-like L' – [4.05] colors, suggesting that their spectral energy distributions peak in between the L' and M' broadband filters. We find no statistically significant difference in HR 8799 cde's color. Atmosphere models assuming thick, patchy clouds appear to better match HR 8799 bcde's photometry than models assuming amore » uniform cloud layer. While non-equilibrium carbon chemistry is required to explain HR 8799 b and c's photometry/spectra, evidence for it from HR 8799 d and e's photometry is weaker. Future, deep-IR spectroscopy/spectrophotometry with the Gemini Planet Imager, SCExAO/CHARIS, and other facilities may clarify whether the planets are chemically similar or heterogeneous.« less
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [10] ;  [11]
  1. Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada)
  2. Department of Astrophysical Science, Princeton University, 4 Ivy Lane, Princeton, NJ 08544 (United States)
  3. European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago (Chile)
  4. Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan)
  5. Department of Astronomy, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan)
  6. Exoplanets and Stellar Astrophysics Laboratory, NASA Goddard Space Flight Center, Code 667, Greenbelt, MD 20771 (United States)
  7. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
  8. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
  9. Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyago, 407-2 Nishigaichi, Sayo, Hyogo 679-5313 (Japan)
  10. School of Engineering, Physics, and Mathematics, University of Dundee, Dundee DD1 4HN (United Kingdom)
  11. National Astronomical Observatory of Japan, 650 N. Aohoku Place, Hilo, HI 96720 (United States)
Publication Date:
OSTI Identifier:
22370026
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 795; 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; CARBON; COLOR; ENERGY SPECTRA; EQUILIBRIUM; IMAGE PROCESSING; INFRARED SPECTRA; LAYERS; LIMITING VALUES; MASS; PHOTOMETRY; PLANETS; RESOLUTION; SATELLITE ATMOSPHERES; SATELLITES; SIGNAL-TO-NOISE RATIO; SPECTROPHOTOMETRY; STARS