Rapidly Spinning Neutron Stars and the Equation of State of Dense Matter

Wednesday, January 29, 2020 11:30 am - 11:30 am EST

Astronomy Seminar Series

Sharon Morsink

Neutron stars are tiny stars with ultra-strong magnetic and gravitational fields and densities larger than nuclear. Their small size and large average densities allow them to spin at very rapid rates, with surface velocities that are a large fraction of the speed of light. The very large gravitational fields and relativistic rotation rates make it necessary to use Einstein's theory of general relativity to describe these stars.  The pulsed X-ray emission from hot spots on the surface of a rotating neutron star contains encoded information about the neutron star’s gravitational field and the properties of the spot’s emission pattern. Disentangling these effects in the pulsed emission seen by X-ray timing observatories such as NICER, ASTROSAT, eXTP, and STROBE-X will allow the determination of the neutron star’s mass and radius, leading (eventually) to a determination of the neutron star equation of state. In this talk I will review some of the aspects of relativity that make rapidly rotating neutron stars excellent targets for determining the equation of state of cold dense matter.  I will introduce the method for extracting the neutron star’s properties from its observed waveform, and highlight some recent X-ray pulsar observations made by the NICER X-ray telescope.

Relativistic astrophysics is the application of the theory of general relativity (the theory of strong gravitational fields) to problems in astrophysics. The strongest gravitational fields in the universe are associated with compact objects (neutron stars and black holes). The main focus is on providing a clearer understanding of the electromagnetic and gravitational radiation produced by compact objects.  Sharon’s  research is theoretical and she uses a mix of analytical and numerical techniques.