Photometric Monitoring of the Coldest Known Brown Dwarf with the Spitzer Space Telescope

Abstract

Because WISE J085510.83$-$071442.5 (hereafter WISE 0855-0714) is the coldest known brown dwarf ($\sim 250$ K) and one of the Sun's closest neighbors (2.2 pc), it offers a unique opportunity for studying a planet-like atmosphere in an unexplored regime of temperature. To detect and characterize inhomogeneities in its atmosphere (e.g., patchy clouds, hot spots), we have performed time-series photometric monitoring of WISE 0855-0714 at 3.6 and 4.5 micron with the Spitzer Space Telescope during two 23~hr periods that were separated by several months. For both bands, we have detected variability with peak-to-peak amplitudes of 4-5% and 3-4% in the first and second epochs, respectively. The light curves are semi-periodic in the first epoch for both bands, but are more irregular in the second epoch. Models of patchy clouds have predicted a large increase in mid-IR variability amplitudes (for a given cloud covering fraction) with the appearance of water ice clouds at $T_{\mathrm{eff}}<$375 K, so if such clouds are responsible for the variability of WISE 0855-0714, then its small amplitudes of variability indicate a very small deviation in cloud coverage between hemispheres. Alternatively, the similarity in mid-IR variability amplitudes between WISE 0855-0714 and somewhat warmer T and Y dwarfs may suggest that they share a common origin for their variability (i.e., not water clouds). In addition to our variability data, we have examined other constraints on the presence of water ice clouds in the atmosphere of WISE 0855-0714, including the recent mid-IR spectrum from \citet{ske16}. We find that robust evidence of such clouds is not yet available.

arXiv comment5 pages, 3 figures, 2 machine readable tables avaiable at https://www.dropbox.com/s/c8vbzcnk5ut8t64/tab1.txt?dl=0 and https://www.dropbox.com/s/olop66rke57fb2m/tab2.txt?dl=0 , respectively. Accepted for publication in The Astrophysical Journal

References in corpus (45)

• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• The Infrared Array Camera (IRAC) for the Spitzer Space Telescope
• The Spitzer Space Telescope Mission
• Precipitating Condensation Clouds in Substellar Atmospheres
• The Evolution of L and T Dwarfs in Color-Magnitude Diagrams
• Absolute Calibration of the Infrared Array Camera on the Spitzer Space Telescope
• The 3.6-8.0 Micron Broadband Emission Spectrum of HD 209458b: Evidence for an Atmospheric Temperature Inversion
• Neglected Clouds in T and Y Dwarf Atmospheres
• The 0.8-14.5 micron Spectra of Mid-L to Mid-T Dwarfs: Diagnostics of Effective Temperature, Grain Sedimentation, Gas Transport, and Surface Gravity
• Point Source Extraction with MOPEX
• Weather on Other Worlds. II. Survey Results: Spots Are Ubiquitous on L and T Dwarfs
• Evidence for Cloud Disruption in the L/T Dwarf Transition
• Activity in Very Cool Stars: Magnetic Dissipation in late-M and L Dwarf Atmospheres
• Distances, Luminosities, and Temperatures of the Coldest Known Substellar Objects
• Spitzer Infrared Spectrograph Observations of M, L, and T Dwarfs
• A Patchy Cloud Model for the L to T Dwarf Transition
• Strong Brightness Variations Signal Cloudy-to-Clear Transition of Brown Dwarfs
• A global cloud map of the nearest known brown dwarf
• Discovery of a ~250 K Brown Dwarf at 2 pc from the Sun
• Water Clouds in Y Dwarfs and Exoplanets
• A Theory for the Radius of the Transiting Giant Planet HD 209458b
• Atmospheric dynamics of brown dwarfs and directly imaged giant planets
• Brown Dwarf Photospheres are Patchy: A Hubble Space Telescope Near-infrared Spectroscopic Survey Finds Frequent Low-level Variability
• New H2 collision-induced absorption and NH3 opacity and the spectra of the coolest brown dwarfs
• $ExtrasolarStorms$: Pressure-dependent Changes In Light Curve Phase In Brown Dwarfs From Simultaneous $Hubble$ and $Spitzer$ Observations
• An independent analysis of the brown dwarf atmosphere monitoring (BAM) data: large-amplitude variability is rare outside the L/T transition
• The Brown dwarf Atmosphere Monitoring (BAM) Project I: The largest near-IR monitoring survey of L- & T-dwarfs
• Spectral Variability from the Patchy Atmospheres of T and Y Dwarfs
• Temperature Fluctuations as a Source of Brown Dwarf Variability
• The First Spectrum of the Coldest Brown Dwarf
• Weather on Other Worlds I: Detection of Periodic Variability in the L3 Dwarf DENIS-P J1058.7-1548 with Precise Multi-Wavelength Photometry
• The First Detection of Photometric Variability in a Y Dwarf: WISE J140518.39+553421.3
• A Monitoring Campaign for Luhman 16AB. I. Detection of Resolved Near-Infrared Spectroscopic Variability
• Indications of Water Clouds in the Coldest Known Brown Dwarf
• The Spectral Energy Distribution of the Coldest Known Brown Dwarf
• Maps of Evolving Cloud Structures in Luhman 16AB from HST Time-Resolved Spectroscopy
• Observed Variability at 1um and 4um in the Y0 Brown Dwarf WISEP J173835.52+273258.9
• NEOWISE-R Observation of the Coolest Known Brown Dwarf
• A New Parallax Measurement for the Coldest Known Brown Dwarf
• Temperature constraints on the coldest brown dwarf known WISE 0855-0714
• The Collapse of the Wien Tail in the Coldest Brown Dwarf? Hubble Space Telescope Near-Infrared Photometry of WISE J085510.83-071442.5
• Measuring High-Precision Astrometry with the Infrared Array Camera on the Spitzer Space Telescope
• Rotation periods and astrometric motions of the Luhman 16AB brown dwarfs by high-resolution lucky-imaging monitoring
• Deep $z$-band observations of the coolest Y dwarf
• A Search for Substellar Companions to the Two Nearest Brown Dwarf Systems

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