ÃÛÌÒTV

I will discuss how we can use observations of accreting neutron stars to constrain the thermal properties of neutron star cores. Neutron stars in close binaries undergo accretion outbursts in which matter transferred from the companion star accretes onto the neutron star for months to years. The added material compresses the star, driving nuclear reactions that heat up the neutron star crust. I will focus on the response of the core to this hot blanket, and how we can use observations of the neutron star temperature after accretion ends to put the first limits on the heat capacity of the neutron star core and learn about its neutrino emissivity. These limits inform us about the composition of matter and superfluidity in the core: current limits rule out a colour-flavour-locked (CFL) phase occupying most of the core, and show that the neutron star in MXB 1659-29 must have a composition and superfluid properties that allow a fast neutrino cooling process.