TY - JOUR
T1 - The brown dwarf atmosphere monitoring (BAM) project
T2 - I. the largest near-IR monitoring survey of L and T dwarfs
AU - Wilson, P. A.
AU - Rajan, A.
AU - Patience, Jennifer
N1 - Funding Information:
Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 188.C-0493. We would like to thank the anonymous referee for valuable suggestions that helped improve this paper. PAW acknowledges support from STFC. J.P. was supported by a Leverhulme research project grant (F/00144/BJ), and funding from an STFC standard grant. This research has made use of the SIMBAD database and VizieR catalogue access tool, CDS, Strasbourg, France. The original description of the VizieR service was published in Ochsenbein et al. 2000, A&AS 143, 23. This research has benefitted from the M, L, T, and Y dwarf compendium housed at DwarfArchives.org. This research made use of Astropy, a community-developed core Python package for Astronomy (Robitaille et al. 2013). We thank F. Pont, R. De Rosa and D. K. Sing for valuable feedback and discussion.
PY - 2014/6
Y1 - 2014/6
N2 - Using the SofI instrument on the 3.5 m New Technology Telescope, we have conducted an extensive near-infrared monitoring survey of an unbiased sample of 69 brown dwarfs spanning the L0 to T8 spectral range, with at least one example of each spectral type. Each target was observed for a 2-4 h period in the J s-band, and the median photometric precision of the data is ∼0.7%. A total of 14 brown dwarfs were identified as variables with min-to-max amplitudes ranging from 1.7% to 10.8% over the observed duration. All variables satisfy a statistical significance threshold with a p-value ≤5% based on comparison with a median reference star light curve. Approximately half of the variables show pure sinusoidal amplitude variations similar to 2MASSJ2139+0220, and the remainder show multi-component variability in their light curves similar to SIMPJ0136+0933. It has been suggested that the L-T transition should be a region of a higher degree of variability if patchy clouds are present, and this survey was designed to test the patchy cloud model with photometric monitoring of both the L-T transition and non-transition brown dwarfs. The measured frequency of variables is 13+10%-4 across the L7-T4 spectral range, indistinguishable from the frequency of variables of the earlier spectral types (30+11-8%), the later spectral types (13+10-4 %), or the combination of all non-transition region brown dwarfs (22+7-5%). The variables are not concentrated in the transition, in a specific colour, or in binary systems. Of the brown dwarfs previously monitored for variability, only ∼60% maintained the state of variability (variable or constant), with the remaining switching states. The 14 variables include 9 newly identified variables that will provide important systems for follow-up multi-wavelength monitoring to further investigate brown dwarf atmosphere physics.
AB - Using the SofI instrument on the 3.5 m New Technology Telescope, we have conducted an extensive near-infrared monitoring survey of an unbiased sample of 69 brown dwarfs spanning the L0 to T8 spectral range, with at least one example of each spectral type. Each target was observed for a 2-4 h period in the J s-band, and the median photometric precision of the data is ∼0.7%. A total of 14 brown dwarfs were identified as variables with min-to-max amplitudes ranging from 1.7% to 10.8% over the observed duration. All variables satisfy a statistical significance threshold with a p-value ≤5% based on comparison with a median reference star light curve. Approximately half of the variables show pure sinusoidal amplitude variations similar to 2MASSJ2139+0220, and the remainder show multi-component variability in their light curves similar to SIMPJ0136+0933. It has been suggested that the L-T transition should be a region of a higher degree of variability if patchy clouds are present, and this survey was designed to test the patchy cloud model with photometric monitoring of both the L-T transition and non-transition brown dwarfs. The measured frequency of variables is 13+10%-4 across the L7-T4 spectral range, indistinguishable from the frequency of variables of the earlier spectral types (30+11-8%), the later spectral types (13+10-4 %), or the combination of all non-transition region brown dwarfs (22+7-5%). The variables are not concentrated in the transition, in a specific colour, or in binary systems. Of the brown dwarfs previously monitored for variability, only ∼60% maintained the state of variability (variable or constant), with the remaining switching states. The 14 variables include 9 newly identified variables that will provide important systems for follow-up multi-wavelength monitoring to further investigate brown dwarf atmosphere physics.
KW - Brown dwarfs
KW - Stars: atmospheres
KW - Stars: low-mass
KW - Techniques: photometric
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U2 - 10.1051/0004-6361/201322995
DO - 10.1051/0004-6361/201322995
M3 - Article
AN - SCOPUS:84902979354
VL - 566
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
SN - 0004-6361
M1 - A111
ER -