Date/Time
Date(s) - 08/10/2008
3:20 pm - 4:20 pm

Title: Mapping the neutron star crust in low mass X-ray binaries

Speaker: Dr. Andrew Cumming

Institute: McGill University

Location: ABB 102

Description:

Long term monitoring of accreting neutron stars has opened up new ways to investigate the physics of dense matter in neutron star interiors. In this talk, I start with a reminder of neutron star structure, including the sequence of nuclear transformations that the accreted hydrogen and helium is predicted to undergo as it is compressed by further accretion towards nuclear density. I then discuss recent work to try to test this picture by “taking the temperature” of the neutron star interior using theoretical models of X-ray observations of neutron stars in low mass X-ray binaries. First, I will show that long duration thermonuclear flashes observed while accretion is ongoing give us a glimpse of conditions in the outer liquid ocean. These conditions are set by burning of the accreted hydrogen by the rp-process, involving heavy nuclei close to the proton drip line. Second, I will show that observations of neutron star cooling after an accretion outburst allow us to map out conditions in the solid crust. In particular, I will show that the current observations constrain the depth at which the neutron star crust transitions from a classical to quantum crystal, and constrain the impurity fraction of the crust.