Quadrupole Moments of Rapidly Rotating Compact Objects in Dilatonic Einstein-Gauss-Bonnet Theory

TL;DR

This paper investigates the quadrupole moments of rapidly rotating black holes and neutron stars within dilatonic Einstein-Gauss-Bonnet theory, revealing significant deviations from Kerr black holes and extending universal relations for neutron stars.

Contribution

It provides the first detailed analysis of quadrupole moments in EGBd theory, highlighting their differences from Kerr solutions and confirming the universality of the I-Q relation in this modified gravity context.

Findings

EGBd black holes have larger quadrupole moments than Kerr black holes.

The I-Q universal relation extends to EGBd neutron stars.

Quadrupole moments are influenced by the dilaton field.

Abstract

We consider rapidly rotating black holes and neutron stars in dilatonic Einstein-Gauss-Bonnet (EGBd) theory and determine their quadrupole moments, which receive a contribution from the dilaton. The quadrupole moment of EGBd black holes can be considerably larger than the Kerr value. For neutron stars, the universality property of the $\hat I$-$\hat Q$ relation between the scaled moment of inertia and the scaled quadrupole moment appears to extend to EGBd theory.