The Hellens and Downs Curve for Gravitational Wave Backgrounds

Gravitational waves have a characteristic way of varying as a function of frequency. And so if pulsars are close together, they have a stronger correlation to the gravitational wave background. But then interestingly, because gravitational waves have this quadrampolar shape, which is like a cosine sort of shape, the signal increases again in distance. So having those two things at the same time makes us very confident that what we're seeing now is evidence for the gravitational wavebackground.