The dynamical status of the galaxy cluster Abell 115

Aims. We present the results of a new spectroscopic and photometric survey of the hot, binary X‐ray cluster A115 at z = 0.193, containing a radio relic. Methods. Our analysis is based on new spectroscopic data obtained at the Telescopio Nazionale Galileo for 115 galaxies and on new photometric data obtained at the Isaac Newton Telescope in a large field. We combine galaxy velocity and position informa tion to select 85 galaxies recognized as cluster members, determine global dynamical properties and detect substructures. Results. We find that A115 appears as a well isolated peak in the redshif t space, with a global line‐of‐sight (LOS) velocity dispersion �v = 1362 +126 −108 km s −1 . Our analysis confirms the presence of two structures of clus ter‐type well recognizable in the plane of the sky and shows that they differ of∼ 2000 km s −1 in the LOS velocity. The northern, high velocity subcluster (A115N) is likely centred on the second brightest cluster galaxy (BCM‐A, coincident with radio source 3C28) and the northern X‐ray peak. The southern, low velocity subcluster (A115S) is likely centred on the first br ightest cluster galaxy (BCM‐B) and the southern X‐ray peak. We estimate