GALEX photometry of the open cluster NGC 752

Ultraviolet photometry from the GALEX mission is compiled for a sample of main sequence stars and red giants in the open cluster NGC 752. This is one of the few ensembles of coveal near-solar abundance FGK stars for which near-ultraviolet and far-ultraviolet magnitudes are available from GALEX. Cluster members are identified on the basis of Gaia proper motion and parallax data. Two-colour diagrams, including $(NUV-B, B-V)$ and $(FUV-B, B-V)$ , are presented by combining the GALEX photometry with Johnson $BV$ photometry. In all diagrams which include the $NUV$ magnitude in one of the colours a clear offset is seen between the unevolved main sequence and the main sequence turn-off stars. However, in the $(FUV-B, B-V)$ diagram the main sequence and the turn-off stars overlap. There is evidence of scatter in the $(FUV-B)$ colours of main sequence stars redward of $(B-V) \sim 0.50$ that may be related to differences in stellar activity. A GALEX-only colour-magnitude diagram of NGC 752 in which $NUV$ apparent magnitude is plotted against the $(FUV-NUV)$ colour shows much less separation of the main sequence turn-off stars and red giants from the dwarf sequence than does a traditional $(V, B-V)$ colour-magnitude diagram. Indeed, in the former diagram the red giants of NGC 752 fall very close to the main sequence.