Abstract
We have conducted a photometric monitoring program of 3 field late-L brown dwarfs using Spitzer/IRAC 4.5 and 8μm bandpasses. The aim of this work is to look for evidences of non-axisymmetric structure in their photospheres. The fact that two out of the three targets exhibit some variations in their light curves in one of the two bandpasses studied suggests an instrumental origin for the detected variations. On the other hand the data may still be consistent with intrinsic variability since the fluxes at different wavelengths come from different vertical regions of the atmosphere. In either case, the present observations provide the most sensitive search to date for structure in the photospheres of late-L dwarfs at mid-IR wavelengths, and our photometry provides stringent upper limits to the extent to which the photospheres of these transition L dwarfs are structured.
