Analysis of the photometric variability of WR 40.

New photometric data on the star WR40 are presented and, together with data already published, are analyzed in a detailed and homogeneous manner in order to investigate the variability of the star. Good evidence is presented for the existence of a periodicity P = 6.250 + or - 0.078 day with a semiamplitude of 0.010 mag in the Stromgren b filter. Only part of the 0.1 mag peak-to-peak variation of the star can be explained in this way and other interesting features of the variability are outlined. The physical origin of the periodicity is discussed.