Infrared Parallaxes for Methane T Dwarfs

By C. Tinney, A. Burgasser, J. D. Kirkpatrick. 2003

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We report final results from our 2.5 yr infrared parallax program carried out with the European Southern Observatory 3.5 m New Technology Telescope and the SOFI infrared camera. Our program targeted precision astrometric observations of 10 T-type brown dwarfs in the J band. Full astrometric solutions (including trigonometric parallaxes) for nine T dwarfs are provided along with proper-motion solutions for a further object. We find that HgCdTe-based infrared cameras are capable of delivering precision differential astrometry. For T dwarfs, infrared observations are to be greatly preferred over the optical, both because they are so much brighter in the infrared, and because their prominent methane absorptions lead to similar effective wavelengths through the J filter for both target and reference stars, which in turn results in a dramatic reduction in differential color refraction effects. We describe a technique for robust bias estimation and linearity correction with the SOFI camera, along with an upper limit to the astrometric distortion of the SOFI optical train. Color-magnitude and spectral type–magnitude diagrams for both L and T dwarfs are presented that show complex and significant structure, with major import for luminosity function and mass function work on T dwarfs. Based on the width of the early L dwarf and late T dwarf color magnitude diagrams, we conclude the brightening of early T dwarfs in the J passband (the "early T hump") is not an age effect, but due to the complexity of brown dwarf cooling curves. Finally, empirical estimates of the "turn on" magnitudes for methane absorption in field T dwarfs and in young stars clusters are provided. These make the interpretation of the T6 dwarf σ Ori J053810.1-023626 as a σ Ori member problematic.

Subfields: Astronomy and Astrophysics, Computational Mechanics

View Paper: https://www.semanticscholar.org/paper/8c81c5cc00d47377bb657bf4489cc6890416e7b1

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Citations in the corpus

SpeX SPECTROSCOPY OF UNRESOLVED VERY LOW MASS BINARIES. I. IDENTIFICATION OF 17 CANDIDATE BINARIES STRADDLING THE L DWARF/T DWARF TRANSITION (2009, background): “More remarkably, surface fluxes in the 1.0–1.3 µm region are observed to increase amongst early-type T dwarfs, the so-called “J-band bump” (Dahn et al. 2002; Tinney et al. 2003).”
FUNDAMENTAL PARAMETERS AND SPECTRAL ENERGY DISTRIBUTIONS OF YOUNG AND FIELD AGE OBJECTS WITH MASSES SPANNING THE STELLAR TO PLANETARY REGIME (2015, background): “…(2013), (16) Saumon et al. (2007), (17) Dahn et al. (2002), (18) Vrba et al. (2004), (19) Leggett et al. (2012), (20) Burgasser et al. (2008c), (21) Tinney et al. (2003), (22) Faherty et al. (2014), (23)Mamajek (2005), (24) Manjavacas et al. (2014), (25) Burningham et al. (2011), (26) Geballe et…”
New spectral types L and T (2005, methodology): “For L and T dwarfs in the field, trigonometric parallaxes have been obtained by Dahn et al. (2002), Tinney et al. (2003), Thorstensen & Kirkpatrick (2003), and Vrba et al. (2004).”
The Field Substellar Mass Function Based on the Full-sky 20 pc Census of 525 L, T, and Y Dwarfs (2020, methodology): “All parallaxes are given on the absolute reference grid; data from Tinney et al. (2003) and Tinney et al. (2014), along with USNO data from Kirkpatrick et al. (2019), were converted from relative to absolute as described in section 8 of Kirkpatrick et al. (2019).”
THE HAWAII INFRARED PARALLAX PROGRAM. I. ULTRACOOL BINARIES AND THE L/T TRANSITION, (2012, methodology): “In the case of 2MASS J1534−2952AB, we retrieved the epochs of the observations from the ESO archive and assumed a range of astrometric precision based on the values given in Tinney et al. (2003), namely (7 mas to 20 mas)/ √ 8 added in quadrature to the DCR offset error of 2–6 mas.”
Meeting the Cool Neighbors. IX. The Luminosity Function of M7-L8 Ultracool Dwarfs in the Field (2006, background): “Trigonometric parallax results show that brown dwarfs brighten from MJ ∼ 15 at spectral type T0 to MJ ∼ 14.5 at type T3/4 (Dahn et al. 2002; Tinney et al. 2003; Vrba et al. 2004).”
WEATHER ON OTHER WORLDS. II. SURVEY RESULTS: SPOTS ARE UBIQUITOUS ON L AND T DWARFS (2014, background): “…the relatively large uncertainties in the proper motions of our targets, determined at the time exclusively from ground-based parallax programs (Tinney et al. 2003; Vrba et al. 2004; Faherty et al. 2009), prevented us from obtaining sufficiently accurate positions to ensure placement on the…”
Binaries and the L Dwarf/T Dwarf Transition (2006, background): “…polynomial toMK data 9 based on photometry (Geballe et al. 2002; Leggett et al. 2002; Knapp et al. 2004) and parallax data (Dahn et al. 2002; Tinney et al. 2003; Vrba et al. 2004) for 26 unresolved field L and T dwarfs with combined uncertainties 0.2 mag; and component absolute magnitudes…”
BANYAN. VII. A NEW POPULATION OF YOUNG SUBSTELLAR CANDIDATE MEMBERS OF NEARBY MOVING GROUPS FROM THE BASS SURVEY (2015, unknown): “…Monet et al. (1992); Pérez-Garrido et al. (2014); Phan Bao et al. (2008); Pinfield et al. (2008); Strauss et al. (1999); Thompson et al. (2013); Tinney et al. (2003, 2014); van Leeuwen (2007); Warren et al. (2007); Wilson et al. (2003); Zapatero Osorio et al. (2014); and van Altena et al.…”
Individual Dynamical Masses of Ultracool Dwarfs (2017, methodology): “However, both Liu et al. (2008) and Konopacky et al. (2010) used the parallax of 73.6 ± 1.2 mas from Tinney et al. (2003) to convert their angular semimajor axes into physical units and thereby compute dynamical masses.”
MID-INFRARED PHOTOMETRY OF COLD BROWN DWARFS: DIVERSITY IN AGE, MASS, AND METALLICITY (2010, background): “…paral- laxes for M, L and T dwarfs in the sample were taken from: Costa et al. (2006), Dahn et al. (2002); the Hipparcos catalog (ESA 1997); Smart et al. (2010, and private communication 2009); Tinney (1996); Tinney et al. (1995, 2003); van Altena, Lee & Hoffleit (1995); Vrba et al. (2004).”