Compact Objects Schedule

CASCA 2013 Schedule for Compact Objects

Compact Objects
Location: Hennings 202 Chair: Sharon Morsink
1100 Heyl, Jeremy The Structure Neutron-Star Magnetic Fields
  If the superconducting nuclear material of a neutron star contains magnetic flux tubes, the magnetic field is likely to vary rapidly on the scales where QED effects are important. We construct a cylindrically symmetric toy model of a flux tube lattice in which the influence of neighbouring flux tubes is taken into account. We find an attractive non-local Casimir force between flux tubes that will dramatically affect the structure of the internal magnetic fields of neutron stars with surface fields weaker than a few trillion gauss. This may have consequences for magnetic field decay and pulsar glitches.
1115 Stevens, Abigail * Using X-ray Light Curves to Constrain the Neutron Star Equation of State
  The equation of state for ultra-dense matter has puzzled astrophysicists for decades. This is because the conditions of ultra-dense matter, such as those found in neutron stars, are not terrestrially replicable. X-ray light curves from low-mass X-ray binary systems, with neutron star primaries, have proven to be useful tools in the study of the neutron star equation of state. Theory predicts that the X-ray light curve resulting from a Type I X-ray burst on the surface of a rapidly rotating neutron star can be used to determine the characteristics of the burst ignition spot and place constraints on the neutron star's mass and radius. We discuss the development of spherical and oblate neutron star models that, providing parameter values, yield an X-ray light curve comparable to that which would be measured by an X-ray timing telescope like RXTE. This simulation code, used with a genetic fitting algorithm, will provide us with an opportunity to disentangle the effects of various aspects of the neutron star and hotspot on the outputted light curve, showing which parameter degeneracies will have the greatest impact on the observable.
1130 Gill, Ramandeep Study of high energy processes in relativistic plasmas near compact sources
  We develop a numerical code to investigate the emission properties of relativistic plasmas near compact objects. The code simulates all high energy processes involved in generating the observed spectra of X-ray binaries, AGN, and Gamma-ray bursts. The interaction of charged particle species and photons is dealt in a self-consistent manner using a Fokker-Planck treatment of the problem. Currently, the code solves time-dependent kinetic equations of homogeneous and isotropic particle and photon distributions in a fixed geometry. We intend to generalize the code further to study anisotropic particle/photon populations.
1145 Vulic, Neven * Searching for Faint X-Ray Binaries in M31
  The population of low-luminosity (< 10^35 erg/s) X-Ray Binaries (XRBs) has been investigated in our Galaxy and M31 but not further. We have used data from the Chandra X-Ray Observatory and the Hubble Space Telescope to investigate the faint population of XRBs in M31. A stacking analysis of the X-ray data at the positions of optically-identified star clusters was completed to probe low-luminosity X-ray sources. We will present preliminary results from the stacking analysis along with an optical counterpart comparison.
1200 pickup, heather Tidally induced type 1a supernovae in white dwarf - intermediate mass black hole binaries
  We investigate the possibility of inducing type 1a supernovae in white dwarf - intermediate mass black hole binaries, through resonantly transferring energy from the orbit to the oscillations of the star or tidally inducing these oscillations through repeated close passages as it orbits. Because the resulting oscillations can be of order unity and contain about 0.1 MeV per nucleon, exceeding the energy required for the ignition of the star by a factor of about 10-30, non-linear damping of the oscillations and other non-linear processes such as shocks may be able to efficiently thermalize this energy culminating in an irregular type 1a supernova. To study this we use a massively parallelized, eulerian hydrodynamics code that allows us to resolve the white dwarf as well as the orbit, with a realistic equation of state employed for the white dwarf to accurately model it's oscillation spectrum, that enables us to observe the consequences of these oscillations upon the orbit and to follow the unstable mass transfer period.
1215 Madsen, Erik * Detecting pulsars in fast, eccentric orbits
  In recent years, many pulsars have been found in globular clusters, many of which are millisecond pulsars (MSPs) in binary systems. Unlike binary MSPs in the Galactic Disk, these are sometimes in eccentric orbits. Standard methods for pulsar detection become less effective for faster orbits, but just how much less effective is an important problem that is not simple to solve. Analytic approaches to this problem that assume circular orbits have been taken in the past, but until this year none had accounted for orbital eccentricity. I am approaching this problem empirically, simulating pulsar data with a wide range of parameters and running standard search algorithms to explore how these parameters affect our sensitivity.