Parallaxes of Southern Extremely Cool objects (PARSEC) II: Spectroscopic Follow-up and Parallaxes of 52 Targets

Abstract

We present near-infrared spectroscopy for 52 ultracool dwarfs, including two newly discovered late-M dwarfs, one new late-M subdwarf candidate, three new L and four new T dwarfs. We also present parallaxes and proper motions for 21 of them. Four of the targets presented here have previous parallax measurements, while all the others are new values. This allow us to populate further the spectral sequence at early types (L0-L4). Combining the astrometric parameters with the new near-infrared spectroscopy presented here, we are able to investigate further the nature of some of the objects. In particular, we find that the peculiar blue L1 dwarf SDSS J133148.92-011651.4 is a metal-poor object, likely a member of the galactic thick disk. We discover a new M subdwarf candidate, 2MASS J20115649-6201127. We confirm the low-gravity nature of EROS-MP J0032-4405, DENIS-P J035726.9-441730, and 2MASS J22134491-2136079. We present two new metal-poor dwarfs: the L4pec 2MASS J19285196-4356256 and the M7pec SIPS2346-5928. We also determine the effective temperature and bolometric luminosity of the 21 targets with astrometric measurements, and we obtain a new polynomial relation between effective temperature and near-infrared spectral type. The new fit suggests a flattening of the sequence at the transition between M and L spectral types. This could be an effect of dust formation, that causes a more rapid evolution of the spectral features as a function of the effective temperature.

Accepted for publication in AJ. 37 pages, 17 figures, 6 tables

References in corpus (25)

• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• The Evolution of L and T Dwarfs in Color-Magnitude Diagrams
• The Hawaii Infrared Parallax Program. I. Ultracool Binaries and the L/T Transition
• On the Luminosity of Young Jupiters
• The First Hundred Brown Dwarfs Discovered by the Wide-field Infrared Survey Explorer (WISE)
• The Discovery of Y Dwarfs Using Data from the Wide-field Infrared Survey Explorer (WISE)
• The 0.8-14.5 micron Spectra of Mid-L to Mid-T Dwarfs: Diagnostics of Effective Temperature, Grain Sedimentation, Gas Transport, and Surface Gravity
• Young L Dwarfs Identified in the Field: A Preliminary Low-Gravity, Optical Spectral Sequence from L0 to L5
• Meeting the Cool Neighbors. IX. The Luminosity Function of M7-L8 Ultracool Dwarfs in the Field
• The Brown Dwarf Kinematics Project (BDKP). III. Parallaxes for 70 Ultracool Dwarfs
• A Sample of Very Young Field L Dwarfs and Implications for the Brown Dwarf "Lithium Test" at Early Ages
• Revised metallicity classes for low-mass stars: dwarfs (dM), subdwarfs (sdM), extreme subdwarfs (esdM), and ultra subdwarfs (usdM)
• Discovery of 11 New T Dwarfs in the Two Micron All-Sky Survey, Including a Possible L/T Transition Binary
• The Young Planet-mass Object 2M1207b: a cool, cloudy, and methane-poor atmosphere
• Finding benchmark brown dwarfs to probe the IMF as a function of time
• Discovery of a T Dwarf Binary with the Largest Known J-Band Flux Reversal
• The Gemini NICI Planet-Finding Campaign: Discovery of a Multiple System Orbiting the Young A Star HD 1160
• Discovery of the benchmark metal poor T8 dwarf BD+01 2920B
• The Properties of the 500 K Dwarf UGPS J072227.51-054031.2, and a Study of the Far-Red Flux of Cold Brown Dwarfs
• New, nearby bright southern ultracool dwarfs
• SSPMJ1102-3431 brown dwarf characterization from accurate proper motion and trigonometric parallax
• The sub-stellar birth rate from UKIDSS
• Southern Infrared Proper Motion Survey II: A sample of low mass stars with μ> 0.1''/yr
• The Solar Neighborhood. XVIII. Discovery of new proper motion stars with 0.40 arcsec yr^-1 > mu >= 0.18 arcsec yr^-1 between declinations -90 degrees and -47 degrees
• Resolved Hubble Space spectroscopy of ultracool binary systems

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