Non-gray, Month-long Brightening of KIC 8462852 in the Immediate Aftermath of a Deep Dip

Abstract

We present an analysis of the results of long-term, multi-band photometric monitoring of the enigmatic star, KIC 8462852. Observations in the B, g′, V, r′, and IC passbands have been acquired at University College London Observatory between 2017 May and 2018 September. We interrogate the wavelength dependence of the ∼month-long dimming and brightening exhibited by the target star over an 85 day interval, immediately following a days-long ∼5% drop in brightness on Julian Date (JD) 2,458,203. Between JD 2,458,215–300 we measure brightness variations which correspond to relative extinctions of , Ag′/AV = 1.16 ± 0.11, Ar′/AV = 0.80 ± 0.25 and AIc/AV = 0.49 ± 0.19, from which we infer an Ångström absorption coefficient of 1.33 ± 0.43 (). As with the days-long “dips”, the wavelength dependence of the longer-term brightness variations must also be associated with extinction arising from a dust distribution containing a substantial fraction of submicron-sized grains. This implies some common mechanism is responsible for the star’s variability over both these short and longer timescales.