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Spitzer Light Curves of the Young, Planetary-mass TW Hya Members 2MASS J11193254–1137466AB and WISEA J114724.10–204021.3

Schneider, Adam C. and Hardegree-Ullman, Kevin K. and Cushing, Michael C. and Kirkpatrick, J. Davy and Shkolnik, Evgenya L. (2018) Spitzer Light Curves of the Young, Planetary-mass TW Hya Members 2MASS J11193254–1137466AB and WISEA J114724.10–204021.3. Astronomical Journal, 155 (6). Art. No. 238. ISSN 0004-6256. doi:10.3847/1538-3881/aabfc2.

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We present Spitzer Space Telescope time-series photometry at 3.6 and 4.5 μm of 2MASS J11193254−1137466AB and WISEA J114724.10−204021.3, two planetary-mass, late-type (~L7) brown dwarf members of the ~10 Myr old TW Hya Association. These observations were taken in order to investigate whether or not a tentative trend of increasing variability amplitude with decreasing surface gravity seen for L3–L5.5 dwarfs extends to later-L spectral types and to explore the angular momentum evolution of low-mass objects. We examine each light curve for variability and find a rotation period of 19.39^(+0.33)_(−0.28) hr and semi-amplitudes of 0.798^(+0.081)_(−0.083)% at 3.6 μm and 1.108^(+0.093)_(−0.094)% at 4.5 μm for WISEA J114724.10−204021.3. For 2MASS J11193254−1137466AB, we find a single period of 3.02^(+0.04)_(−0.03) hr with semi-amplitudes of 0.230^(+0.036)_(−0.035)% at 3.6 μm and 0.453 ± 0.037% at 4.5 μm, which we find is possibly due to the rotation of one component of the binary. Combining our results with 12 other late-type L dwarfs observed with Spitzer from the literature, we find no significant differences between the 3.6 μm amplitudes of low surface gravity and field gravity late-type L brown dwarfs at Spitzer wavelengths, and find tentative evidence (75% confidence) of higher amplitude variability at 4.5 μm for young, late-type Ls. We also find a median rotation period of young brown dwarfs (10–300 Myr) of ~10 hr, more than twice the value of the median rotation period of field-age brown dwarfs (~4 hr), a clear signature of brown dwarf rotational evolution.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Schneider, Adam C.0000-0002-6294-5937
Hardegree-Ullman, Kevin K.0000-0003-3702-0382
Cushing, Michael C.0000-0001-7780-3352
Kirkpatrick, J. Davy0000-0003-4269-260X
Shkolnik, Evgenya L.0000-0002-7260-5821
Additional Information:© 2018. The American Astronomical Society. Received 2018 March 17; revised 2018 April 17; accepted 2018 April 18; published 2018 May 17. We wish to thank the anonymous referee for a helpful report that improved the quality of this work. A.S. and E.S. appreciate support from NASA/Habitable Worlds grant NNX16AB62G (PI E. Shkolnik). 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. Software: photutils (Bradley et al. 2016), emcee (Foreman-Mackey et al. 2013), lifelines (Davidson-Pilon 2016).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:brown dwarfs
Issue or Number:6
Record Number:CaltechAUTHORS:20180518-130813607
Persistent URL:
Official Citation:Adam C. Schneider et al 2018 AJ 155 238
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86453
Deposited By: George Porter
Deposited On:18 May 2018 20:21
Last Modified:15 Nov 2021 20:38

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