The brown dwarf atmosphere monitoring (BAM) project - II. Multi-epoch monitoring of extremely cool brown dwarfs

A. Rajan, Jennifer Patience, P. A. Wilson, J. Bulger, R. J. De Rosa, K. Ward-Duong, C. Morley, F. Pont, Rogier Windhorst

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

With the discovery of Y dwarfs by the WISE mission, the population of field brown dwarfs now extends to objects with temperatures comparable to those of Solar system planets. To investigate the atmospheres of these newly identified brown dwarfs, we have conducted a pilot study monitoring an initial sample of three late-T dwarfs (T6.5, T8 and T8.5) and one Y dwarf (Y0) for infrared photometric variability at multiple epochs. With J-band imaging, each target was observed for a period of 1.0-4.5 h per epoch, which covers a significant fraction of the expected rotational period. These measurements represent the first photometric monitoring for these targets. For three of the four targets (2M1047, Ross 458C and WISE0458), multiepoch monitoring was performed, with the time span between epochs ranging from a few hours to ∼2 years. During the first epoch, the T8.5 target WISE0458 exhibited variations with a remarkable min-to-max amplitude of 13 per cent, while the second epoch light curve taken ∼2 years later did not note any variability to a 3 per cent upper limit. With an effective temperature of ∼600 K, WISE0458 is the coldest variable brown dwarf published to date, and combined with its high and variable amplitude makes it a fascinating target for detailed followup. The three remaining targets showed no significant variations, with a photometric precision between 0.8 and 20.0 per cent, depending on the target brightness. Combining the new results with previous multi-epoch observations of brown dwarfs with spectral types of T5 or later, the currently identified variables have locations on the colour-colour diagram better matched by theoretical models incorporating cloud opacities rather than cloud-free atmospheres. This preliminary result requires further study to determine if there is a definitive link between variability among late-T dwarfs and their location on the colour-colour diagram.

Original languageEnglish (US)
Pages (from-to)3775-3783
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Volume448
Issue number4
DOIs
StatePublished - 2015

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time measurement
atmospheres
atmosphere
monitoring
color-color diagram
diagram
solar system
free atmosphere
Wide-field Infrared Survey Explorer
planet
temperature
project
opacity
light curve
planets
brightness

Keywords

  • Brown dwarfs
  • General
  • Low-mass
  • Stars
  • Stars
  • Variables

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

The brown dwarf atmosphere monitoring (BAM) project - II. Multi-epoch monitoring of extremely cool brown dwarfs. / Rajan, A.; Patience, Jennifer; Wilson, P. A.; Bulger, J.; De Rosa, R. J.; Ward-Duong, K.; Morley, C.; Pont, F.; Windhorst, Rogier.

In: Monthly Notices of the Royal Astronomical Society, Vol. 448, No. 4, 2015, p. 3775-3783.

Research output: Contribution to journalArticle

Rajan, A. ; Patience, Jennifer ; Wilson, P. A. ; Bulger, J. ; De Rosa, R. J. ; Ward-Duong, K. ; Morley, C. ; Pont, F. ; Windhorst, Rogier. / The brown dwarf atmosphere monitoring (BAM) project - II. Multi-epoch monitoring of extremely cool brown dwarfs. In: Monthly Notices of the Royal Astronomical Society. 2015 ; Vol. 448, No. 4. pp. 3775-3783.
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T1 - The brown dwarf atmosphere monitoring (BAM) project - II. Multi-epoch monitoring of extremely cool brown dwarfs

AU - Rajan, A.

AU - Patience, Jennifer

AU - Wilson, P. A.

AU - Bulger, J.

AU - De Rosa, R. J.

AU - Ward-Duong, K.

AU - Morley, C.

AU - Pont, F.

AU - Windhorst, Rogier

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N2 - With the discovery of Y dwarfs by the WISE mission, the population of field brown dwarfs now extends to objects with temperatures comparable to those of Solar system planets. To investigate the atmospheres of these newly identified brown dwarfs, we have conducted a pilot study monitoring an initial sample of three late-T dwarfs (T6.5, T8 and T8.5) and one Y dwarf (Y0) for infrared photometric variability at multiple epochs. With J-band imaging, each target was observed for a period of 1.0-4.5 h per epoch, which covers a significant fraction of the expected rotational period. These measurements represent the first photometric monitoring for these targets. For three of the four targets (2M1047, Ross 458C and WISE0458), multiepoch monitoring was performed, with the time span between epochs ranging from a few hours to ∼2 years. During the first epoch, the T8.5 target WISE0458 exhibited variations with a remarkable min-to-max amplitude of 13 per cent, while the second epoch light curve taken ∼2 years later did not note any variability to a 3 per cent upper limit. With an effective temperature of ∼600 K, WISE0458 is the coldest variable brown dwarf published to date, and combined with its high and variable amplitude makes it a fascinating target for detailed followup. The three remaining targets showed no significant variations, with a photometric precision between 0.8 and 20.0 per cent, depending on the target brightness. Combining the new results with previous multi-epoch observations of brown dwarfs with spectral types of T5 or later, the currently identified variables have locations on the colour-colour diagram better matched by theoretical models incorporating cloud opacities rather than cloud-free atmospheres. This preliminary result requires further study to determine if there is a definitive link between variability among late-T dwarfs and their location on the colour-colour diagram.

AB - With the discovery of Y dwarfs by the WISE mission, the population of field brown dwarfs now extends to objects with temperatures comparable to those of Solar system planets. To investigate the atmospheres of these newly identified brown dwarfs, we have conducted a pilot study monitoring an initial sample of three late-T dwarfs (T6.5, T8 and T8.5) and one Y dwarf (Y0) for infrared photometric variability at multiple epochs. With J-band imaging, each target was observed for a period of 1.0-4.5 h per epoch, which covers a significant fraction of the expected rotational period. These measurements represent the first photometric monitoring for these targets. For three of the four targets (2M1047, Ross 458C and WISE0458), multiepoch monitoring was performed, with the time span between epochs ranging from a few hours to ∼2 years. During the first epoch, the T8.5 target WISE0458 exhibited variations with a remarkable min-to-max amplitude of 13 per cent, while the second epoch light curve taken ∼2 years later did not note any variability to a 3 per cent upper limit. With an effective temperature of ∼600 K, WISE0458 is the coldest variable brown dwarf published to date, and combined with its high and variable amplitude makes it a fascinating target for detailed followup. The three remaining targets showed no significant variations, with a photometric precision between 0.8 and 20.0 per cent, depending on the target brightness. Combining the new results with previous multi-epoch observations of brown dwarfs with spectral types of T5 or later, the currently identified variables have locations on the colour-colour diagram better matched by theoretical models incorporating cloud opacities rather than cloud-free atmospheres. This preliminary result requires further study to determine if there is a definitive link between variability among late-T dwarfs and their location on the colour-colour diagram.

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KW - Stars

KW - Variables

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