New gravitational memories

The conventional gravitational memory effect is a relative displacement in the position of two detectors induced by radiative energy flux. we find a new type of gravitational ‘spin memory’ in which beams on clockwise and counterclockwise orbits acquire a relative delay induced by radiative angular momentum flux. it has recently been shown that the displacement memory formula is a fourier transform in time of weinberg’s soft graviton theorem. here we see that the spin memory formula is a fourier transform in time of the recently-discovered subleading soft graviton theorem.