Rotational Corrections to Neutron-Star Radius Measurements from Thermal Spectra

Understand

We calculate the rotational broadening in the observed thermal spectra of neutron stars spinning at moderate rates in the Hartle-Thorne approximation.

• These calculations accurately account for the effects of the second-order Doppler boosts as well as for the oblate shapes and the quadrupole moments of the neutron stars.
• We find that fitting the spectra and inferring the bolometric fluxes under the assumption that a star is not rotating causes an underestimate of the inferred fluxes and, thus, radii.
• The correction depends on the stellar spin, radius, and observer's inclination.