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THE GEMINI NICI PLANET-FINDING CAMPAIGN: DISCOVERY OF A SUBSTELLAR L DWARF COMPANION TO THE NEARBY YOUNG M DWARF CD–35 2722

2011; IOP Publishing; Volume: 729; Issue: 2 Linguagem: Inglês

10.1088/0004-637x/729/2/139

ISSN

1538-4357

Autores

Z. Wahhaj, Michael C. Liu, Beth Biller, Fraser Clarke, E. Nielsen, Laird M. Close, T. L. Hayward, Eric E. Mamajek, Michael C. Cushing, Trent J. Dupuy, Matthias Tecza, Niranjan Thatte, Mark Chun, Christ Ftaclas, Markus Hartung, I. Neill Reid, Evgenya L. Shkolnik, S. H. P. Alencar, Pawel Artymowicz, Alan P. Boss, E. M. de Gouveia Dal Pino, J. Gregorio‐Hetem, Shigeru Ida, Marc J. Kuchner, D. N. C. Lin, Douglas W. Toomey,

Tópico(s)

Astro and Planetary Science

Resumo

We present the discovery of a wide (67 AU) substellar companion to the nearby (21 pc) young solar-metallicity M1 dwarf CD−35 2722, a member of the ≈100 Myr AB Doradus association. Two epochs of astrometry from the NICI Planet-Finding Campaign confirm that CD−35 2722 B is physically associated with the primary star. Near-IR spectra indicate a spectral type of L4±1 with a moderately low surface gravity, making it one of the coolest young companions found to date. The absorption lines and near-IR continuum shape of CD−35 2722 B agree especially well the dusty field L4.5 dwarf 2MASS J22244381−0158521, while the near-IR colors and absolute magnitudes match those of the 5 Myr old L4 planetary-mass companion, 1RXS J160929.1−210524 b. Overall, CD−35 2722 B appears to be an intermediate-age benchmark for L dwarfs, with a less peaked H-band continuum than the youngest objects and near-IR absorption lines comparable to field objects. We fit Ames-Dusty model atmospheres to the near-IR spectra and find Teff= 1700–1900 K and log(g)= 4.5 ± 0.5. The spectra also show that the radial velocities of components A and B agree to within ±10 km s−1, further confirming their physical association. Using the age and bolometric luminosity of CD−35 2722 B, we derive a mass of 31 ± 8 MJup from the Lyon/Dusty evolutionary models. Altogether, young late-M to mid-L type companions appear to be overluminous for their near-IR spectral type compared with field objects, in contrast to the underluminosity of young late-L and early-T dwarfs.

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