The I-Q relations for rapidly rotating neutron stars in $f(R)$ gravity

Understand

In the present paper we study the behavior of the normalized $I$-$Q$ relation for neutron stars in a particular class of $f(R)$ theories of gravity, namely the $R^2$ gravity that is one of the most natural and simplest extensions of general relativity in the strong field regime.

• We study both the slowly and rapidly rotating cases.
• The results show that the $I$-$Q$ relation remain nearly equation of state independent for fixed values of the normalized rotational parameter, but the deviations from universality can be a little bit larger compared to the general relativistic case.
• What is the most interesting in our studies, is that the differences with the pure Einstein's theory can be large reaching above 20\%.