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 ∼ 10 -10 erg/cm 2 /s. For VIRGO, we detect a non-zero signal between 0.75 to 1.50 MeV having marginal significance of about 2.5 σ , with the observed energy flux equal to ∼ 10 -9 ergs/cm 2 /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.