Pulse Profiles from Spinning Neutron Stars in the Hartle-Thorne Approximation

Abstract

We present a new numerical algorithm for the calculation of pulse profiles from spinning neutron stars in the Hartle-Thorne approximation. Our approach allows us to formally take into account the effects of Doppler shifts and aberration, of frame dragging, as well as of the oblateness of the stellar surface and of its quadrupole moment. We confirm an earlier result that neglecting the oblateness of the neutron-star surface leads to ~5-30% errors in the calculated profiles and further show that neglecting the quadrupole moment of its spacetime leads to ~1-5% errors at a spin frequency of 600 Hz. We discuss the implications of our results for the measurements of neutron-star masses and radii with upcoming X-ray missions, such as NASA's NICER and ESA's LOFT.