Higher-derivative Heterotic Kerr-Sen Black Holes

TL;DR

This paper derives four-derivative corrections to heterotic Kerr-Sen black holes, revealing modifications in multipole moments that could help distinguish string theory effects in gravitational wave observations.

Contribution

It provides the first computation of higher-derivative corrections to heterotic Kerr-Sen black holes, including their multipole moments, and compares them to Kerr and Kerr-Newman solutions.

Findings

Multipole moments differ from Kerr at four-derivative level.

Corrections distinguish heterotic black holes from Kerr-Newman.

Potential observational signatures in gravitational wave data.

Abstract

We obtain the four-derivative corrections to the Kerr-Sen solution in heterotic supergravity, which includes the Gibbons-Maeda-Garfinkle-Horowitz-Strominger solution as a limiting case. In particular, we first embed the Kerr solution into heterotic supergravity and compute the higher-derivative corrections. We then obtain the corrections to the Kerr-Sen solution by performing an $O(2,1)$ boost of the Kerr solution, which, in contrast to the two-derivative case, requires field redefinitions to make the $O(2,1)$ invariance of the action manifest. Finally, we compute the multipole moments and find that they are distinct from those of the Kerr solution at the four-derivative level. We also find that the multipole moments are distinct from those of the Kerr-Newman solution in Einstein-Maxwell theory at the four-derivative level, even for the most general choice of four-derivative corrections. This gives a way to experimentally distinguish traces of string theory in gravitational wave data.