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The unknown $\gamma$-ray excess in the northwest region of Arp 220 wasrevisited by analyzing $\sim$11.8 years of the \textit{Fermi} Large AreaTelescope (\textit{Fermi}-LAT) data in this study. We found that its photonflux was approximately three times higher than that of the previous study inthe 0.2-100 GeV band, and the corresponding significance level$\sim8.15\sigma$was approximately four times higher than before. The light curves of 15 and 45time bins from the whole time all showed two active periods, and thevariability of the second period was more significant than that of the firstperiod. The spectral indices from the two active periods were not statisticallydifferent and were close to the range of $\gamma$-ray flat-spectrum radioquasars observed by \textit{Fermi}-LAT. Because the position of CRATESJ153246+234400 was consistent with the best-fit position of our analysis, wesuggest that CRATES J153246+234400 is more likely a $\gamma$-ray counterpartfor the variational region. For Arp 220, there was no significant variabilityin the $\gamma$-ray emission.

The Likely Counterpart to $\gamma$-Ray Excess from The Northwest Region of Arp 220