Preliminary parallaxes of 40 L and T dwarfs from the US naval observatory infrared astrometry program

F. J. Vrba, A. A. Henden, C. B. Luginbuhl, H. H. Guetter, J. A. Munn, B. Canzian, A. J. Burgasser, J. Davy Kirkpatrick, Xiaohui Fan, T. R. Geballe, D. A. Golimowski, G. R. Knapp, S. K. Leggett, D. P. Schneider, J. Brinkmann

Research output: Contribution to journalArticle

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Abstract

We present preliminary trigonometric parallaxes and proper motions for 22 L dwarfs and 18 T dwarfs measured using the ASTROCAM infrared imager on the US Naval Observatory (USNO) 1.55 m Strand Astrometric Reflector. The results presented here are based on observations obtained between 2000 September and 2002 November; about half of the objects have an observational time baseline of Δt = 1.3 yr and half Δt = 2.0 yr. Despite these short time baselines, the astrometric quality is sufficient to produce significant new results, especially for the nearer T dwarfs. Seven objects are in common with the USNO optical CCD parallax program for quality control and seven in common with the European Southern Observatory 3.5m New Technology Telescope parallax program. We compare astrometric quality with both of these programs. Relative to absolute parallax corrections are made by employing Two Micron All Sky Survey and/or Sloan Digital Sky Survey photometry for reference-frame stars. We combine USNO infrared and optical parallaxes with the best available California Institute of Technology (CIT) system photometry to determine M J, M H, and M K values for 37 L dwarfs between spectral types L0 and L8 and 19 T dwarfs between spectral types T0.5 and T8 and present selected absolute magnitude versus spectral type and color diagrams, based on these results. Luminosities and temperatures are estimated for these objects. Of special interest are the distances of several objects that are at or near the L-T dwarf boundary so that this important transition can be better understood. The previously reported early to mid T dwarf luminosity excess is clearly confirmed and found to be present at J, H, and K. The large number of objects that populate this luminosity-excess region indicate that it cannot be due entirely to selection effects. The T dwarf sequence is extended to M j ≈ 16.9 by 2MASS J041519-0935, which, at d = 5.74 pc, is found to be the least luminous [log(L/L ) = -5.58] and coldest (T eff ≈ 760 K) brown dwarf known. Combining results from this paper with earlier USNO CCD results we find that, in contrast to the L dwarfs, there are no examples of lowvelocity (V tan < 20 km s -1) T dwarfs. This is consistent with the T dwarfs in this study being generally older than the L dwarfs. We briefly discuss future directions for the USNO infrared astrometry program.

Original languageEnglish (US)
Pages (from-to)2948-2968
Number of pages21
JournalAstronomical Journal
Volume127
Issue number5 1781
DOIs
StatePublished - May 2004

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astrometry
observatories
observatory
parallax
luminosity
photometry
charge coupled devices
proper motion
quality control
European Southern Observatory
strands
reflectors
diagrams
programme
telescopes
color
stars
diagram
temperature

Keywords

  • Astrometry
  • Color-magnitude diagrams
  • Stars: distances
  • Stars: late-type
  • Stars: low-mass, brown dwarfs

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Vrba, F. J., Henden, A. A., Luginbuhl, C. B., Guetter, H. H., Munn, J. A., Canzian, B., ... Brinkmann, J. (2004). Preliminary parallaxes of 40 L and T dwarfs from the US naval observatory infrared astrometry program. Astronomical Journal, 127(5 1781), 2948-2968. https://doi.org/10.1086/383554

Preliminary parallaxes of 40 L and T dwarfs from the US naval observatory infrared astrometry program. / Vrba, F. J.; Henden, A. A.; Luginbuhl, C. B.; Guetter, H. H.; Munn, J. A.; Canzian, B.; Burgasser, A. J.; Kirkpatrick, J. Davy; Fan, Xiaohui; Geballe, T. R.; Golimowski, D. A.; Knapp, G. R.; Leggett, S. K.; Schneider, D. P.; Brinkmann, J.

In: Astronomical Journal, Vol. 127, No. 5 1781, 05.2004, p. 2948-2968.

Research output: Contribution to journalArticle

Vrba, FJ, Henden, AA, Luginbuhl, CB, Guetter, HH, Munn, JA, Canzian, B, Burgasser, AJ, Kirkpatrick, JD, Fan, X, Geballe, TR, Golimowski, DA, Knapp, GR, Leggett, SK, Schneider, DP & Brinkmann, J 2004, 'Preliminary parallaxes of 40 L and T dwarfs from the US naval observatory infrared astrometry program', Astronomical Journal, vol. 127, no. 5 1781, pp. 2948-2968. https://doi.org/10.1086/383554
Vrba FJ, Henden AA, Luginbuhl CB, Guetter HH, Munn JA, Canzian B et al. Preliminary parallaxes of 40 L and T dwarfs from the US naval observatory infrared astrometry program. Astronomical Journal. 2004 May;127(5 1781):2948-2968. https://doi.org/10.1086/383554
Vrba, F. J. ; Henden, A. A. ; Luginbuhl, C. B. ; Guetter, H. H. ; Munn, J. A. ; Canzian, B. ; Burgasser, A. J. ; Kirkpatrick, J. Davy ; Fan, Xiaohui ; Geballe, T. R. ; Golimowski, D. A. ; Knapp, G. R. ; Leggett, S. K. ; Schneider, D. P. ; Brinkmann, J. / Preliminary parallaxes of 40 L and T dwarfs from the US naval observatory infrared astrometry program. In: Astronomical Journal. 2004 ; Vol. 127, No. 5 1781. pp. 2948-2968.
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T1 - Preliminary parallaxes of 40 L and T dwarfs from the US naval observatory infrared astrometry program

AU - Vrba, F. J.

AU - Henden, A. A.

AU - Luginbuhl, C. B.

AU - Guetter, H. H.

AU - Munn, J. A.

AU - Canzian, B.

AU - Burgasser, A. J.

AU - Kirkpatrick, J. Davy

AU - Fan, Xiaohui

AU - Geballe, T. R.

AU - Golimowski, D. A.

AU - Knapp, G. R.

AU - Leggett, S. K.

AU - Schneider, D. P.

AU - Brinkmann, J.

PY - 2004/5

Y1 - 2004/5

N2 - We present preliminary trigonometric parallaxes and proper motions for 22 L dwarfs and 18 T dwarfs measured using the ASTROCAM infrared imager on the US Naval Observatory (USNO) 1.55 m Strand Astrometric Reflector. The results presented here are based on observations obtained between 2000 September and 2002 November; about half of the objects have an observational time baseline of Δt = 1.3 yr and half Δt = 2.0 yr. Despite these short time baselines, the astrometric quality is sufficient to produce significant new results, especially for the nearer T dwarfs. Seven objects are in common with the USNO optical CCD parallax program for quality control and seven in common with the European Southern Observatory 3.5m New Technology Telescope parallax program. We compare astrometric quality with both of these programs. Relative to absolute parallax corrections are made by employing Two Micron All Sky Survey and/or Sloan Digital Sky Survey photometry for reference-frame stars. We combine USNO infrared and optical parallaxes with the best available California Institute of Technology (CIT) system photometry to determine M J, M H, and M K values for 37 L dwarfs between spectral types L0 and L8 and 19 T dwarfs between spectral types T0.5 and T8 and present selected absolute magnitude versus spectral type and color diagrams, based on these results. Luminosities and temperatures are estimated for these objects. Of special interest are the distances of several objects that are at or near the L-T dwarf boundary so that this important transition can be better understood. The previously reported early to mid T dwarf luminosity excess is clearly confirmed and found to be present at J, H, and K. The large number of objects that populate this luminosity-excess region indicate that it cannot be due entirely to selection effects. The T dwarf sequence is extended to M j ≈ 16.9 by 2MASS J041519-0935, which, at d = 5.74 pc, is found to be the least luminous [log(L/L ⊙) = -5.58] and coldest (T eff ≈ 760 K) brown dwarf known. Combining results from this paper with earlier USNO CCD results we find that, in contrast to the L dwarfs, there are no examples of lowvelocity (V tan < 20 km s -1) T dwarfs. This is consistent with the T dwarfs in this study being generally older than the L dwarfs. We briefly discuss future directions for the USNO infrared astrometry program.

AB - We present preliminary trigonometric parallaxes and proper motions for 22 L dwarfs and 18 T dwarfs measured using the ASTROCAM infrared imager on the US Naval Observatory (USNO) 1.55 m Strand Astrometric Reflector. The results presented here are based on observations obtained between 2000 September and 2002 November; about half of the objects have an observational time baseline of Δt = 1.3 yr and half Δt = 2.0 yr. Despite these short time baselines, the astrometric quality is sufficient to produce significant new results, especially for the nearer T dwarfs. Seven objects are in common with the USNO optical CCD parallax program for quality control and seven in common with the European Southern Observatory 3.5m New Technology Telescope parallax program. We compare astrometric quality with both of these programs. Relative to absolute parallax corrections are made by employing Two Micron All Sky Survey and/or Sloan Digital Sky Survey photometry for reference-frame stars. We combine USNO infrared and optical parallaxes with the best available California Institute of Technology (CIT) system photometry to determine M J, M H, and M K values for 37 L dwarfs between spectral types L0 and L8 and 19 T dwarfs between spectral types T0.5 and T8 and present selected absolute magnitude versus spectral type and color diagrams, based on these results. Luminosities and temperatures are estimated for these objects. Of special interest are the distances of several objects that are at or near the L-T dwarf boundary so that this important transition can be better understood. The previously reported early to mid T dwarf luminosity excess is clearly confirmed and found to be present at J, H, and K. The large number of objects that populate this luminosity-excess region indicate that it cannot be due entirely to selection effects. The T dwarf sequence is extended to M j ≈ 16.9 by 2MASS J041519-0935, which, at d = 5.74 pc, is found to be the least luminous [log(L/L ⊙) = -5.58] and coldest (T eff ≈ 760 K) brown dwarf known. Combining results from this paper with earlier USNO CCD results we find that, in contrast to the L dwarfs, there are no examples of lowvelocity (V tan < 20 km s -1) T dwarfs. This is consistent with the T dwarfs in this study being generally older than the L dwarfs. We briefly discuss future directions for the USNO infrared astrometry program.

KW - Astrometry

KW - Color-magnitude diagrams

KW - Stars: distances

KW - Stars: late-type

KW - Stars: low-mass, brown dwarfs

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U2 - 10.1086/383554

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