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Sharp spectral structures in the $\gamma$-ray band are an important darkmatter (DM) signature. Previously, a tentative line feature at $\sim 43~{\rmGeV}$ is reported in 16 nearby galaxy clusters (GCls) with 7.1 years ofFermi-LAT data, whose TS value is $\sim 16.7$. In this work, we search for linesignals and box-shaped structures using the stacked data from those 16 GClswith 11.4-yr P8R3 data. There is still a hint at $\sim {42~\rm GeV}$, dominatedby the radiation of Virgo and Ophiuchus clusters. Though the TS value was highup to 21.2 in October 2016, currently it has dropped to 13.1. Moreover, the TSvalue at $\sim {42~\rm GeV}$ decreases to 2.4 when the EDISP2 data are excludedfrom the analysis. Consequently, we do not find any statistically significantline-like signal and then set up the 95% confidence level upper limits on thethermally averaged cross section of DM annihilating into double photons. Thesame line search has been carried out for an alternative GCl sample from theTwo Micron All-Sky Survey but no any evidence has been found. We also searchfor box-shaped features in those 16 baseline GCls. No signal is found as welland the corresponding upper limits on the annihilation cross section are given.

Search for line-like and box-shaped spectral features from nearby galaxy clusters with 11.4 years of Fermi LAT data