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We report the detection of a large amplitude MIR outburst in the white dwarf(WD) 0145+234 in the NEOWISE Survey data. The source had a stable MIR fluxbefore 2018, and was brightened by about 1.0 magnitude in the W1 and W2 bandswithin half a year and has been continuously brightening since then. Nosignificant variations are found in the optical photometry data during the sameperiod. This suggests that this MIR outburst is caused by recent replenishingor redistribution of dust, rather than intrinsic variations of the WD. SEDmodeling of 0145+234 suggests that there was already a dust disk around the WDin the quiescent state, and both of the temperature and surface area of thedisk evolved rapidly since the outburst. The dust temperature was about 1770Kin the initial rising phase, close to the sublimation temperature of silicategrains, and gradually cooled down to around 1150K, while the surface areaincreased by a factor of about 6 during the same period. The inferred closestdistance of dust to the WD is within the tidal disruption radius of agravitationally bounded asteroid. We estimated the dust mass to be between$3\times10^{15}$ to $3\times10^{17}$ $\rho/(1 \mathrm g~cm^{-3})$ kg forsilicate grains of a power-law size distribution with a high cutoff size from0.1 to 1000 microns. We interpret this as a possible tidal breakup of anexo-asteroid by the WD. Further follow-up observations of this rare event mayprovide insights on the origin of dust disk and metal pollution in some whitedwarfs.

An On-going Mid-infrared Outburst in the White Dwarf 0145+234: Catching in Action of Tidal Disruption of an Exoasteroid?