Neutron-star Interior Composition ExploreR

One of the most significant developments in the measurement of the dense matter equation of state is going to come from the NICER detector, built as an astrophysics payload that will go on the International Space Station in 2016. Instead of focusing on spectroscopy, NICER will take a very different approach to measuring neutron star radii, based on the shapes and amplitudes of the pulsed emission observed from neutron star surfaces in multiple wavebands. Because of light bending effects in general relativity, these waveforms encode information about the neutron star space-time, and therefore, its radius and mass. We work on the most sophisticated calculations of these waveforms and methods, similar to image reconstruction and Doppler tomography, for extracting radius information from the upcoming data. We will be applying these techniques to the pulsars that NICER will observe in the next 2 years.



Our group works on the most sophisticated models of the waveforms produced by polar caps on rotation-powered neutron stars. The General Relativistic calculations take into account the Doppler effects, the oblateness of the star, the quadrupole moment of the spacetime, and the shapes of the polar caps to produce realistic waveforms for NICER targets. We also work on the statistical techniques to break the degeneracies between the inferred parameters and determine the neutron star radius and mass with high precision.