Investigating Brown Dwarf Variability at 3.4 & 4.6µm with

Abstract. Multi-epoch photometry from AllWISE provides the opportu-nity to investigate variability at 3.4 and 4.6µm for most known brown dwarfs. WISE observed the same patch of sky repeatedly and within a day’s time, roughly 12 observations were obtained on a given patch of sky; then, an-other 12 were obtained roughly six months later when that patch of sky was again in view. For most of the sky, AllWISE contains two separate epochs of about a dozen observations each, although ∼30 % of the sky has three such epochs available in AllWISE. With the AllWISE multi-epoch photometry of ∼1500 known M, L, T, and Y dwarfs, I computed the Stetson J Index and quantified variability as a function of spectral type. I found that the average single-exposure photometric uncertainty in AllWISE (∼0.2 magnitudes) is too large to robustly identify flux variability smaller than ∼20%. However, multi-epoch photometry from AllWISE remains a useful resource in cases where flux variability is known to be present with large amplitudes, or for bright nearby objects with lower photometric uncertainties. 1. Summary The study of brown dwarf flux variability has progressed rapidly. Early observa-tions of variability proved its existence (Bailer-Jones & Mundt, 2001; Gelino et al., 2002; Clarke et al., 2008), but more recent studies have measured periodic-ity, wavelength/pressure dependencies, and long term evolution (Artigau et al.