English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Because WISE J085510.83$-$071442.5 (hereafter WISE 0855-0714) is the coldestknown brown dwarf ($\sim250$ K) and one of the Sun's closest neighbors (2.2pc), it offers a unique opportunity for studying a planet-like atmosphere in anunexplored regime of temperature. To detect and characterize inhomogeneities inits atmosphere (e.g., patchy clouds, hot spots), we have performed time-seriesphotometric monitoring of WISE 0855-0714 at 3.6 and 4.5 micron with the SpitzerSpace Telescope during two 23~hr periods that were separated by several months.For both bands, we have detected variability with peak-to-peak amplitudes of4-5% and 3-4% in the first and second epochs, respectively. The light curvesare semi-periodic in the first epoch for both bands, but are more irregular inthe second epoch. Models of patchy clouds have predicted a large increase inmid-IR variability amplitudes (for a given cloud covering fraction) with theappearance of water ice clouds at $T_{\rm eff}<$375 K, so if such clouds areresponsible for the variability of WISE 0855-0714, then its small amplitudes ofvariability indicate a very small deviation in cloud coverage betweenhemispheres. Alternatively, the similarity in mid-IR variability amplitudesbetween WISE 0855-0714 and somewhat warmer T and Y dwarfs may suggest that theyshare a common origin for their variability (i.e., not water clouds). Inaddition to our variability data, we have examined other constraints on thepresence of water ice clouds in the atmosphere of WISE 0855-0714, including therecent mid-IR spectrum from \citet{ske16}. We find that robust evidence of suchclouds is not yet available.

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