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Previously, we have shown in Li et al. (2018) that very weak $\gamma$-rayexcesses ($\sim 2\sigma$) appear in some Milky Way dwarf spheroidal galaxies(dSphs, including candidates) and the combination analysis of 12 nearby dSphsyields a local significance of $>4\sigma$. In this work, we adopt a longer dataset (i.e., the 12 years of Fermi-LAT data), the latest Fermi-LAT software aswell as background models to update the searches of $\gamma$-ray emission fromthese sources. Very weak $\gamma$-ray excesses ($>$ 2 $\sigma$) are found inthe directions of three dSphs, including Reticulum II, Bootes II and Willman 1.In the direction of Reticulum II, the peak TS value of the excess reaches$\sim$11. However, different from the previous analysis with the 9 years ofFermi-LAT data, now the location of the gamma-ray emission is significantlyaway from the center of Reticulum II because of the enhancement of "offset"$\gamma$-rays above 10 GeV since 2017. The detected weak excess is likely dueto the contamination of an astrophysical $\gamma$-ray source with a TS value of$\sim 22$, irrelevant to the dark matter inside Reticulum II. The possibleexcesses in the directions of Bootes II and Willman 1 are weaker with lowerpeak TS values ($\sim 7$). If interpreted as annihilation of dark matterparticles into $\tau^+\tau^-$, the dark mass mass of $m_\chi \sim 14$ GeV and$\sim 80$ GeV are found for Bootes II and Willman 1, respectively. Much moredata are needed to clarify whether these two potential signals are real andthen reveal their origins.

Search for gamma-ray emission from the 12 nearby dwarf spheroidal galaxies with 12 years of Fermi-LAT data