Not a message, but rather, natural emissions. Stars generate HUGE magnetic fields. Planets orbiting and spinning within these fields disrupt them, and can produce radio waves as a result. Analysis of these emissions can tell astronomers more about the exoplanet. It is yet another clever technique to tease out info from these staggeringly distant objects.
/johnny
What I’m going to have to look up is the definition of a radio light curve. The term doesn’t make sense to me.