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2013ApJ...772...79A - Astrophys. J., 772, 79 (2013/August-1)

A near-infrared spectroscopic study of young field ultracool dwarfs.

ALLERS K.N. and LIU M.C.

Abstract (from CDS):

We present a near-infrared (0.9-2.4 µm) spectroscopic study of 73 field ultracool dwarfs having spectroscopic and/or kinematic evidence of youth (~10-300 Myr). Our sample is composed of 48 low-resolution (R ~ 100) spectra and 41 moderate-resolution spectra (R ≳ 750-2000). First, we establish a method for spectral typing M5-L7 dwarfs at near-IR wavelengths that is independent of gravity. We find that both visual and index-based classification in the near-IR provides consistent spectral types with optical spectral types, though with a small systematic offset in the case of visual classification at J and K band. Second, we examine features in the spectra of ∼10 Myr ultracool dwarfs to define a set of gravity-sensitive indices based on FeH, VO, K I, Na I, and H-band continuum shape. We then create an index-based method for classifying the gravities of M6-L5 dwarfs that provides consistent results with gravity classifications from optical spectroscopy. Our index-based classification can distinguish between young and dusty objects. Guided by the resulting classifications, we propose a set of low-gravity spectral standards for the near-IR. Finally, we estimate the ages corresponding to our gravity classifications.

Abstract Copyright:

Journal keyword(s): brown dwarfs - infrared: stars - planets and satellites: atmospheres - stars: low-mass

Simbad objects: 138

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2019.09.16-01:21:17

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