A Note on Soft Factors for Closed String Scattering

Abstract: In this note, it is shown that closed string graviton scattering amplitudes obey the same subleading soft limit as field theory graviton scattering amplitudes. The result is derived using a combination of recent results and methods including the subleading soft expansion for type I open string gluon disk scattering amplitudes, the single value projection for multiple $\zeta$ values, and the KLT relations in field and string theory.