A pilot search for MeV gamma-ray emission from five galaxy clusters using archival COMPTEL data

We search for MeV gamma-ray emission between 0.75-30 MeV from five galaxy clusters, viz. Coma, VIRGO, SPT-CL J2012-5649, Bullet, and El Gordo, using archival data from the COMPTEL telescope. For this purpose we use three search templates: point source, radial disk and radial Gaussian. We do not detect any signals from Coma, SPT-CL J2012-5649, Bullet and El Gordo clusters with the 95% c.l. photon energy flux limit $\sim {10}^{-10}\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{/}\mathrm{c}{\mathrm{m}}^2\mathrm{/}\mathrm{s}$. For VIRGO, we detect a non-zero signal between 0.92 to 1.63 MeV having marginal significance of about $2.5\sigma$, with the observed energy flux $\sim {10}^{-9}\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{s}\mathrm{/}\mathrm{c}{\mathrm{m}}^2\mathrm{/}\mathrm{s}$. However, we do not confirm the previously reported evidence in literature for a gamma-ray line from Coma and VIRGO clusters between 5-7 MeV.