By combining H \upalpha flux measurements from the Sloan Digital Sky Survey ( SDSS ) with UV flux observations from the Galaxy Evolution Explorer ( GALEX ) , we examine the environmental dependence ( through central/satellite distinction ) of the rapid quenching and rejuvenation of galaxies . H \upalpha emissions trace the most massive stars , thereby indicating star-formation on timescales of \sim 10 Myr , while UV emission traces star-formation on timescales of \sim 100 Myr . These varying timescales are exploited to probe the most recent star-formation histories of galaxies . In this work , we define a class of transient galaxies which have UV emission typical of star formation but negligible H \upalpha emission . We find that the occurrence of these transients has a strong stellar mass dependence in both the satellite and central population . However , while at stellar masses greater than M _ { * } \sim 10 ^ { 10 } M _ { \odot } they occur with equal frequency regardless of environmental class , at lower stellar masses they are more common in satellites only , with an excess of about 1 per cent across all low stellar mass galaxies . These satellite transients also have a strong halo mass and group-centric radial dependence suggesting they are driven by an environmental process . Finally , we show that ‘ rejuvenating ’ galaxies , those with H \upalpha emission but not UV emission , are few in number and do not have a strong difference in their occurrence rate in centrals or satellites . These unique probes point to an environmental quenching mechanism which occurs on short timescales after the satellite has been in the group environment for a significant time – consistent with ‘ delayed-then-rapid ’ quenching .