PLANETS AROUND LOW-MASS STARS (PALMS). VI. DISCOVERY of A REMARKABLY RED PLANETARY-MASS COMPANION to the AB DOR MOVING GROUP CANDIDATE 2MASS J22362452+4751425

Brendan P. Bowler, Michael C. Liu, Dimitri Mawet, Henry Ngo, Lison Malo, Gregory N. Mace, Jacob N. McLane, Jessica R. Lu, Isaiah I. Tristan, Sasha Hinkley, Lynne A. Hillenbrand, Evgenya Shkolnik, Björn Benneke, William M J Best

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Abstract

We report the discovery of an extremely red planetary-mass companion to 2MASS J22362452+4751425, a ≈0.6 M o late-K dwarf likely belonging to the ∼120 Myr AB Doradus moving group. 2M2236+4751 b was identified in multi-epoch NIRC2 adaptive optics imaging at Keck Observatory at a separation of 37, or 230 ±20 AU in projection at the kinematic distance of 63 ±5 pc to its host star. Assuming membership in the AB Dor group, as suggested from its kinematics, the inferred mass of 2M2236+4751 b is 11-14 M Jup. Follow-up Keck/OSIRIS K-band spectroscopy of the companion reveals strong CO absorption similar to other faint red L dwarfs and lacks signs of methane absorption, despite having an effective temperature of ≈900-1200 K. With a (J-K)MKO color of 2.69 ±0.12 mag, the near-infrared slope of 2M2236+4751 b is redder than all of the HR 8799 planets and instead resembles the ≈23 Myr isolated planetary-mass object PSO J318.5-22, implying that similarly thick photospheric clouds can persist in the atmospheres of giant planets at ages beyond 100 Myr. In near-infrared color-magnitude diagrams, 2M2236+4751 b is located at the tip of the red L dwarf sequence and appears to define the "elbow" of the AB Dor substellar isochrone separating low-gravity L dwarfs from the cooler young T dwarf track. 2M2236+4751 b is the reddest substellar companion to a star and will be a valuable benchmark to study the shared atmospheric properties of young low-mass brown dwarfs and extrasolar giant planets.

Original languageEnglish (US)
Article number18
JournalAstronomical Journal
Volume153
Issue number1
DOIs
StatePublished - Jan 1 2017

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Keywords

  • planetary systems
  • planets and satellites: atmospheres
  • stars: individual (2MASS J22362452+4751425)
  • stars: low-mass

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Bowler, B. P., Liu, M. C., Mawet, D., Ngo, H., Malo, L., Mace, G. N., McLane, J. N., Lu, J. R., Tristan, I. I., Hinkley, S., Hillenbrand, L. A., Shkolnik, E., Benneke, B., & Best, W. M. J. (2017). PLANETS AROUND LOW-MASS STARS (PALMS). VI. DISCOVERY of A REMARKABLY RED PLANETARY-MASS COMPANION to the AB DOR MOVING GROUP CANDIDATE 2MASS J22362452+4751425. Astronomical Journal, 153(1), [18]. https://doi.org/10.3847/1538-3881/153/1/18