TY - JOUR
T1 - Spitzer Light Curves of the Young, Planetary-mass TW Hya Members 2MASS J11193254-1137466AB and WISEA J114724.10-204021.3
AU - Schneider, Adam C.
AU - Hardegree-Ullman, Kevin K.
AU - Cushing, Michael C.
AU - Kirkpatrick, J. Davy
AU - Shkolnik, Evgenya
N1 - Funding Information:
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.
Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved..
PY - 2018/6
Y1 - 2018/6
N2 - 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.
AB - 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.
KW - brown dwarfs
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U2 - 10.3847/1538-3881/aabfc2
DO - 10.3847/1538-3881/aabfc2
M3 - Article
AN - SCOPUS:85048144598
SN - 0004-6256
VL - 155
JO - Astronomical Journal
JF - Astronomical Journal
IS - 6
M1 - 238
ER -