Volume 601, May 2017
|Number of page(s)||11|
|Section||Planets and planetary systems|
|Published online||03 May 2017|
Mid-infrared characterization of the planetary-mass companion ROXs 42B b
1 ETH Zürich, Institut für Astronomie, Wolfgang-Pauli-Strasse 27, 8093 Zürich, Switzerland
2 Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
3 Department of Physics and Astronomy, University of Hawaii-Hilo, 200 W Kawili St, Hilo, HI 96720, USA
4 Lawrence Livermore National Laboratory, 7000 East Ave, Livermore, CA 94550, USA
5 Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, USA
6 National Astronomical Observatory of Japan, Subaru Telescope, Hilo, HI, USA
7 Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA
8 Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA
9 Institute for Physics/IGAM, NAWI Graz, University of Graz, Universitätsplatz 5/II, 8010 Graz, Austria
10 Space Telescope Science institute, Baltimore, MD 21218, USA
11 Institut de Recherche sur les Exoplanètes et Université de Montréal, Montréal, QC, Canada
12 Faculty of Science, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada
13 Institute for Astronomy, 34 ’Ohi’a Ku St. Pukalani, HI, USA
Received: 24 October 2016
Accepted: 18 February 2017
We present new Keck/NIRC2 3–5 μm infrared photometry of the planetary-mass companion to ROXS 42B in L′, and for the first time in Brackett-α (Brff) and in Ms-band. We combine our data with existing near-infrared photometry and K-band (2–2.4 μm) spectroscopy and compare these data with models and other directly imaged planetary-mass objects using forward modeling and retrieval methods in order to characterize the atmosphere of ROXS 42B b. The ROXS 42B b 1.25–5 μm spectral energy distribution most closely resembles that of GSC 06214 B and κ And b, although it has a slightly bluer Ks−Ms color than GSC 06214 B and thus currently lacks evidence of a circumplanetary disk. We cannot formally exclude the possibility that any of the tested dust-free/dusty/cloudy forward models describe the atmosphere of ROXS 42B b well. However, models with substantial atmospheric dust/clouds yield temperatures and gravities that are consistent when fit to photometry and spectra separately, whereas dust-free model fits to photometry predict temperatures/gravities inconsistent with the ROXS 42B b K-band spectrum and vice-versa. Atmospheric retrieval on the 1–5 μm photometry places a limit on the fractional number density of CO2 of log (nCO2) < 2.7, but provides no other constraints so far. We conclude that ROXS 42B b has mid-IR photometric features that are systematically different from other previously observed planetary-mass and field objects of similar temperature. It remains unclear whether this is in the range of the natural diversity of targets at the very young (~2 Myr) age of ROXS 42B b or unique to its early evolution and environment.
Key words: stars: pre-main sequence / planets and satellites: individual: ROXS42Bb / planets and satellites: detection
© ESO, 2017
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