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A Sensitive Search for Variability in Late L Dwarfs: The Quest for Weather

Morales-Calderón, M. and Stauffer, J. R. and Kirkpatrick, J. Davy and Carey, S. and Gelino, C. R. and Barrado y Navascués, D. and Rebull, L. and Lowrance, P. and Marley, M. S. and Charbonneau, D. and Patten, B. M. and Megeath, S. T. and Buzasi, D. (2006) A Sensitive Search for Variability in Late L Dwarfs: The Quest for Weather. Astrophysical Journal, 653 (2). pp. 1454-1463. ISSN 0004-637X.

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We have conducted a photometric monitoring program of three field late L brown dwarfs (DENIS-P J0255-4700, 2MASS J0908+5032, and 2MASS J2244+2043) looking for evidence of nonaxisymmetric structure or temporal variability in their photospheres. The observations were performed using Spitzer IRAC 4.5 and 8 μm bandpasses and were designed to cover at least one rotational period of each object; 1 σ rms uncertainties of less than 3 mmag at 4.5 μm and around 9 mmag at 8 μm were achieved. Two out of the three objects studied exhibit some modulation in their light curves at 4.5 μm—but not 8 μm—with periods of 7.4 hr (DENIS 0255) and 4.6 hr (2MA 2244) and peak-to-peak amplitudes of 10 and 8 mmag. Although the lack of detectable 8 μm variation suggests an instrumental origin for the detected variations, the data may nevertheless still be consistent with intrinsic variability, since the shorter wavelength IRAC bandpasses probe more deeply into late L dwarf atmospheres than the longer wavelengths. A cloud feature occupying a small percentage (1%-2%) of the visible hemisphere could account for the observed amplitude of variation. If, instead, the variability is indeed instrumental in origin, then our nonvariable L dwarfs could be either completely covered with clouds or objects whose clouds are smaller and uniformly distributed. Such scenarios would lead to very small photometric variations. Follow-up IRAC photometry at 3.6 and 5.8 μm bandpasses should distinguish between the two cases. In any event, the present observations provide the most sensitive search to date for structure in the photospheres of late L dwarfs at mid-IR wavelengths, and our photometry provides stringent upper limits to the extent to which the photospheres of these transition L dwarfs are structured.

Item Type:Article
Related URLs:
URLURL TypeDescription
Stauffer, J. R.0000-0003-3595-7382
Kirkpatrick, J. Davy0000-0003-4269-260X
Carey, S.0000-0002-0221-6871
Rebull, L.0000-0001-6381-515X
Lowrance, P.0000-0001-8014-0270
Marley, M. S.0000-0002-5251-2943
Charbonneau, D.0000-0002-9003-484X
Megeath, S. T.0000-0001-7629-3573
Additional Information:Copyright is not claimed for this article. Received 2006 June 2; accepted 2006 July 21. We acknowledge use of the L and T dwarf archives at, maintained by two of us (J. D. K. and C.R.G.) and Adam Burgasser. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. M. M.-C. also acknowledges the funding provided by the Spitzer Visiting Graduate Students Fellowship Program. Facilities: Spitzer ( IRAC)
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Spitzer Visiting Graduate Student FellowshipUNSPECIFIED
Subject Keywords:stars: individual (DENIS-P J0255–4700, 2MASS J0908+5032, 2MASS J2244+2043); stars: low-mass, brown dwarfs; stars: variables: other
Issue or Number:2
Record Number:CaltechAUTHORS:20110616-112409859
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Official Citation:A Sensitive Search for Variability in Late L Dwarfs: The Quest for Weather M. Morales-Calderón et al. 2006 ApJ 653 1454
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:24032
Deposited By: Jason Perez
Deposited On:16 Jun 2011 18:52
Last Modified:26 Feb 2020 19:02

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