Speaker
Edward Brown
(MIchigan State University/Joint Institute for Nuclear Astrophysics)
Description
Many neutron stars accrete H- and He-rich matter from a stellar companion. Over the lifetime of the binary,
enough matter can be transferred to replace the crust of neutron star. As the material is compressed, the rising
electron Fermi energy induces electron captures. We calculate the evolution of a fluid element being compressed
to neutron drip under conditions appropriate for the crust of an accreting neutron star. We consider different
initial distributions of nuclei (X-ray burst and superburst ashes) and allow for electron captures into excited
states. The heating from these reactions sets the temperature of the neutron star crust at depths where
explosive burning of carbon (observed as a superburst) occurs, thus providing a possible constraint on the
heating from these captures. A
second constraint comes from neutron stars that accrete intermittently; when the accretion halts, the surface is
detectable with X-ray telescopes such as Chandra and XMM. We calculate the evolution of the X-ray luminosity
following the end of an accretion outburst using our new crust models.
Author
Edward Brown
(MIchigan State University/Joint Institute for Nuclear Astrophysics)
Co-authors
Prof.
Hendrik Schatz
(MIchigan State University/Joint Institute for Nuclear Astrophysics)
Prof.
Karl-Ludwig Kratz
(Universität Mainz)
Dr
Peter Möller
(Los Alamos National Laboratory)
Dr
Sanjib Gupta
(MIchigan State University/Joint Institute for Nuclear Astrophysics)
