Name/Affiliation: Gregory N. Mace (UCLA)
Brown Dwarf Variability in Multi-Epoch WISE Photometry
The discussion of brown dwarf variability has shifted from initial identification to examining durations and amplitudes across the M, L, T, and Y spectral types. Rotational periods, phase shifts between infrared passbands, and variations in amplitude are all tracers of underlying physical traits that are not fully understood. We employ multi-epoch photometry from the Wide-field Infrared Survey Explorer (WISE) at 3.4 and 4.6 microns to investigate brown dwarf variability at these wavelengths. From a Sun-synchronous polar orbit, WISE observed overlapping fields on subsequent orbits and obtained about a dozen observations in ~24 hours. As Earth continued in its orbit around the Sun, each patch of the sky received about a day of coverage, and over the course of ~13 months WISE completed more than two all-sky passes. This provides us with roughly a dozen photometric measurements spread over a day, followed by a similar sampling roughly six months later. From a census of ~1500 known brown dwarfs, we quantify variability on these timescales as a function of spectral type. We especially discuss subsets of this census like the unusually red and blue L dwarfs and the L/T transition.