Mid-infrared characterization of the planetary-mass companion ROXs 42B b

Sebastian Daemgen, Kamen Todorov, Jasmin Silva, Derek Hand, Eugenio V. Garcia, Thayne Currie, Adam S. Burrows, Keivan G. Stassun, Thorsten Ratzka, John H. Debes, David Lafreniere, Ray Jayawardhana, Serge Correia

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


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.

Original languageEnglish (US)
Article numberA65
JournalAstronomy and Astrophysics
StatePublished - May 1 2017

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Planets and satellites: detection
  • Planets and satellites: individual: ROXS42Bb
  • Stars: pre-main sequence


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