Can the string scale be related to the cosmic baryon asymmetry?

In a previous work, a mechanism was presented by which baryon asymmetry can be generated during inflation from elliptically polarized gravitons. Nonetheless, the mechanism only generated a realistic baryon asymmetry under special circumstances, which requires an enhancement of the lepton number from an unspecified GUT. In this paper we provide a stringy embedding of this mechanism, demonstrating that if the model-independent axion is the source of the gravitational waves responsible for the lepton asymmetry, one can observationally constrain the string scale and coupling.