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Title: AN INDEPENDENT ANALYSIS OF THE BROWN DWARF ATMOSPHERE MONITORING (BAM) DATA: LARGE-AMPLITUDE VARIABILITY IS RARE OUTSIDE THE L/T TRANSITION

Abstract

Observations of variability can provide valuable information about the processes of cloud formation and dissipation in brown dwarf atmospheres. Here we report the results of an independent analysis of archival data from the Brown dwarf Atmosphere Monitoring (BAM) program. Time series data for 14 L and T dwarfs reported to be significantly variable over timescales of hours were analyzed. We confirm large-amplitude variability (amplitudes >2%) for 4 out of 13 targets and place upper limits of 0.7%-1.6% on variability in the remaining sample. For two targets we find evidence of weak variability at amplitudes of 1.3% and 1.6%. Based on our revised classification of variable objects in the BAM study, we find strong variability outside the L/T transition to be rare at near infrared wavelengths. From a combined sample of 81 L0-T9 dwarfs from the revised BAM sample and the variability survey of Radigan et al., we infer an overall observed frequency for large-amplitude variability outside the L/T transition of 3.2{sub −1.8}{sup +2.8}%, in contrast to 24{sub −9}{sup +11}% for L9-T3.5 spectral types. We conclude that while strong variability is not limited to the L/T transition, it occurs more frequently in this spectral type range, indicative of larger or moremore » highly contrasting cloud features at these spectral types.« less

Authors:
 [1]
  1. Space Telescope Science Institute, 3700 San Martin Drive Baltimore MD 21218 (United States)
Publication Date:
OSTI Identifier:
22364797
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 797; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; CLASSIFICATION; CLOUDS; DWARF STARS; MONITORING; NEAR INFRARED RADIATION; STELLAR ATMOSPHERES

Citation Formats

Radigan, Jacqueline. AN INDEPENDENT ANALYSIS OF THE BROWN DWARF ATMOSPHERE MONITORING (BAM) DATA: LARGE-AMPLITUDE VARIABILITY IS RARE OUTSIDE THE L/T TRANSITION. United States: N. p., 2014. Web. doi:10.1088/0004-637X/797/2/120.
Radigan, Jacqueline. AN INDEPENDENT ANALYSIS OF THE BROWN DWARF ATMOSPHERE MONITORING (BAM) DATA: LARGE-AMPLITUDE VARIABILITY IS RARE OUTSIDE THE L/T TRANSITION. United States. https://doi.org/10.1088/0004-637X/797/2/120
Radigan, Jacqueline. 2014. "AN INDEPENDENT ANALYSIS OF THE BROWN DWARF ATMOSPHERE MONITORING (BAM) DATA: LARGE-AMPLITUDE VARIABILITY IS RARE OUTSIDE THE L/T TRANSITION". United States. https://doi.org/10.1088/0004-637X/797/2/120.
@article{osti_22364797,
title = {AN INDEPENDENT ANALYSIS OF THE BROWN DWARF ATMOSPHERE MONITORING (BAM) DATA: LARGE-AMPLITUDE VARIABILITY IS RARE OUTSIDE THE L/T TRANSITION},
author = {Radigan, Jacqueline},
abstractNote = {Observations of variability can provide valuable information about the processes of cloud formation and dissipation in brown dwarf atmospheres. Here we report the results of an independent analysis of archival data from the Brown dwarf Atmosphere Monitoring (BAM) program. Time series data for 14 L and T dwarfs reported to be significantly variable over timescales of hours were analyzed. We confirm large-amplitude variability (amplitudes >2%) for 4 out of 13 targets and place upper limits of 0.7%-1.6% on variability in the remaining sample. For two targets we find evidence of weak variability at amplitudes of 1.3% and 1.6%. Based on our revised classification of variable objects in the BAM study, we find strong variability outside the L/T transition to be rare at near infrared wavelengths. From a combined sample of 81 L0-T9 dwarfs from the revised BAM sample and the variability survey of Radigan et al., we infer an overall observed frequency for large-amplitude variability outside the L/T transition of 3.2{sub −1.8}{sup +2.8}%, in contrast to 24{sub −9}{sup +11}% for L9-T3.5 spectral types. We conclude that while strong variability is not limited to the L/T transition, it occurs more frequently in this spectral type range, indicative of larger or more highly contrasting cloud features at these spectral types.},
doi = {10.1088/0004-637X/797/2/120},
url = {https://www.osti.gov/biblio/22364797}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 797,
place = {United States},
year = {Sat Dec 20 00:00:00 EST 2014},
month = {Sat Dec 20 00:00:00 EST 2014}
}