J/A+A/566/A111 Brown dwarf atmosphere monitoring (BAM) (Wilson+, 2014)
The brown dwarf atmosphere monitoring (BAM) project.
I. The largest near-IR monitoring survey of L and T dwarfs.
Wilson P.A., Rajan A., Patience J.
<Astron. Astrophys. 566, A111 (2014)>
=2014A&A...566A.111W 2014A&A...566A.111W
ADC_Keywords: Stars, dwarfs ; Stars, variable ; Photometry
Keywords: techniques: photometric - brown dwarfs - stars: low-mass -
stars: atmospheres
Abstract:
Using the SofI instrument on the 3.5m 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 hour period in the Js-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.
Description:
Target and master reference star light curves for the BAM sample. This
data is used to generate the light curves in Fig. 5.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 80 17 Variables identified in this study
lcs.dat 56 113 Variable objects light curves
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- SName Short name
13 A1 --- q_Name [AB] Variability confidence (1)
15- 37 A23 --- Name Star full name
39- 42 A4 --- SpType MK spectral type
44- 47 F4.2 h Dur [1.9/3.4] Observation duration
49 I1 --- Nref [3/8] Number of reference stars used
51- 52 I2 --- dof [4/12] Number of degrees of freedom
54- 57 F4.1 --- chi2 [1.8/19] Reduced χ2 value
59- 61 F3.1 --- eta [1/4] Reduced robust median statistic η (1)
63- 66 F4.2 % Q [0.3/1.6] Photometric uncertainty
68- 71 F4.2 % p [0/10] p-value (1)
73- 76 F4.1 % Amp [1/11] Amplitude of variation (2)
78- 80 F3.1 % e_Amp [0.5/2] rms uncertainty on Amp
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Note (1): Variability donfidence based on p-value (probability of being
constant) and the reduced median statistic η (normalized deviations
from the median values. The confidence class is defined as:
A = Variables with p-value ≤5% and η≥1.0
B = Variables with 5%< p-value <=10% and {eta}>=1.0
Note (2): These peak-to-trough amplitudes are calculated as the difference
between the minimum and maximum points in the light curve. In some cases,
these might represent the lower limit of the true amplitude, especially for
brown dwarfs which exhibit variability on longer time scales.
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Byte-by-byte Description of file: lcs.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- SName Short name of object, as in table3
13- 20 F8.6 d Time [0/0.14] Days since first Data point
22- 29 F8.6 --- Target [0.95/1.07] Target flux
31- 38 F8.6 --- e_Target [0.002/0.012] Target flux uncertainty
40- 47 F8.6 --- Master [0.96/1.05] Master reference flux
49- 56 F8.6 --- e_Master [0.0008/0.012] Master reference flux uncertainty
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Acknowledgements:
Paul A. Wilson, paw(at)astro.ex.ac.uk
(End) Patricia Vannier [CDS] 10-Jun-2014