THE FIRST DETECTION OF PHOTOMETRIC VARIABILITY IN A Y DWARF: WISE J140518.39+553421.3

Journal Article · Wed Jun 01 00:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/823/2/152· OSTI ID:22666217

Cushing, Michael C.; Hardegree-Ullman, Kevin K.; Trucks, Jesica L. ^[1]; Morley, Caroline V.; Fortney, Jonathan J. ^[2]; Gizis, John E. ^[3]; Marley, Mark S.; Gelino, Christopher R. ^[4]; Kirkpatrick, J. Davy ^[5]; Mace, Gregory N. ^[6]

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1. The University of Toledo, 2801 West Bancroft Street, Mailstop 111, Toledo, OH 43606 (United States)
2. Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
3. Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)
4. NASA Ames Research Center, Moffett Field, CA 94035 (United States)
5. Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States)
6. Department of Astronomy, The University of Texas, Austin, TX 78712 (United States)

We present the first detection of the photometric variability in a spectroscopically confirmed Y dwarf. The Infrared Array Camera on board the Spitzer Space Telescope was used to obtain time series photometry of WISE J140518.39+553421.3 at 3.6 and 4.5 μ m over a 24-hr period at two different epochs separated by 149 days. Variability is evident at 4.5 μ m in the first epoch and at 3.6 and 4.5 μ m in the second epoch, which suggests that the underlying cause or causes of this variability change on the timescales of months. The second-epoch [3.6] and [4.5] light curves are nearly sinusoidal in form, in phase, have periods of roughly 8.5 hr, and have semi-amplitudes of 3.5%. We find that a simple geometric spot model with a single bright spot reproduces these observations well. We also compare our measured semi-amplitudes of the second-epoch light curves to predictions of the static, one-dimensional, partly cloudy, and hot spot models of Morley and collaborators, and find that neither set of models can reproduce the observed [3.6] and [4.5] semi-amplitudes simultaneously. Therefore, more advanced two-dimensional or three-dimensional models that include time-dependent phenomena like vertical mixing, cloud formation, and thermal relaxation are sorely needed in order to properly interpret our observations.

• OSTI ID: 22666217
• Journal Information: Astrophysical Journal, Vol. 823, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
AMPLITUDES
CAMERAS
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
DETECTION
DWARF STARS
INFRARED RADIATION
MASS
MIXING
ONE-DIMENSIONAL CALCULATIONS
PHOTOMETRY
RELAXATION
SPACE
STARS
TELESCOPES
THREE-DIMENSIONAL CALCULATIONS
TIME DEPENDENCE
TWO-DIMENSIONAL CALCULATIONS
VISIBLE RADIATION