Colloquium Seminar: Thermal relaxation in accreting neutron stars: Unravelling the nuclear physics and plasma physics
Speaker: Alessandro Roggero, INT
Location: Auditorium
Time: 14:00
Neutron stars in low-mass X-Ray binaries (LMXBs) undergo long phases of accretion, years to decades, followed by a period of quiescence during which little to no accretion is occourring. Compression of the crust from the accreted material triggers nonequilibrium reactions like electron capture on nuclei and pycno-nuclear (ie. pressure induced) fusion which heat the inner layers of the crust. After the end of accretion the thermal relaxation of the crust has been monitored for several years. As I will explain in this talk, these measurements are extremely valuable to understand transport and thermal properties of dense matter. A particularly uncertain property of accreted crusts is the thermal conductivity. In this talk I will show how one can use Path Integral Monte Carlo (PIMC) simulations to faithfully constrain the low temperature thermal conductivity of the multi component plasma of rp-process ashes expected in the outer crust. In particular, this is achieved by expressing the non-trivial contribution to the response of the system purely in terms of correlation functions in "euclidean time", thus avoiding the numerically-unstable analytical continuation to real time. These new results further amplify the tension between microscopic models of the crust composition and cooling observations strongly suggesting that the crust is more pure than previously thought.