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Reading the Record of Ancient Impacts
Thursday 31 October 2013, 11:30


11:30 - 12:00: Charla de Michael Gabler

Title: Neutron star seismology with magnetar oscillations

Neutron stars are unique astrophysical laboratories that allow to study the behavior of matter at supranuclear densities. The analysis of their oscillation spectra is one possibility to gain information on their interior. We study the magneto-elastic oscillations of highly magnetized neutron stars (magnetars) which are believed to be the origin of quasi-periodic oscillations observed in giant flares of soft gamma-ray repeaters. Our simulations covering the origin of the oscillations in the stellar interior and a possible modulation mechanism in the exterior suggest the presence of superfluid species in the core of the magnetar. The star is simulated with a GRMHD code which we extended by description of the solid crust and superfluid effects in the core. For the exterior emission mechanism we built a new Monte-Carlo Code to describe resonant cyclotron scattering which is coupled to a Particle-in-Line Code that calculates the consistent momentum distribution of the charge carriers in the magnetosphere.

12:00 - 12:30: Charla de Bruno Peres

Title: Towards improving numerical simulations of core-collapse supernovae

Two different paths that represent an improvement in the numerical simulations of core-collapse supernovae will be explored. The first one consists on taking into account the presence of hyperons in the hot and dense matter. To test this, I run simulations up to black hole formation. Results including phase transition to hyperonic matter and gravitational waves extraction will be shown. The second proposed path is to treat the general relativistic Boltzmann equation, unavoidable for an accurate treatment of the neutrinos, with spectral methods, in an attempt to be less demanding in computational power than usual finite differences codes. Test cases will be shown.

12:30 - 13:30: Charla Peter Goldreich

Title: Reading the Record of Ancient Impacts

Debris from asteroids and comets continually bombards the Earth. Large impacts launch ejecta on trajectories that transport it thousands of kilometers from the impact site. These events are recorded in discrete layers of sub-millimeter size spherules in sea floor sediments. Larger, rarer, and interestingly shaped objects are found on land. I will describe the physical processes that occur in energetic impacts. Emphasis will be given to the mechanisms that determine the sizes and shapes of the ejecta and the cooling of the fireball. Analogies with structure formation in an expanding universe following a hot big bang will be exploited.




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