Type: 
SSO Seminar
Date-Time: 
Wednesday, May 20, 2015 - 16:00 to 17:00
Location: 
Weniger 304
Event Speaker: 
Atul Chhotray and Christopher Mauney
Local Contact: 
Guenter Schneider
Abstract: 

Monte Carlo Simulations of Gamma-Ray Burst Prompt Emission (Atul Chhotray)

GRBs (Gamma-Ray Bursts) are one of the most powerful and farthest explosions in the universe. One of the crucial questions plaguing the study of GRBs is the mysterious mechanism responsible for the prompt gamma-ray emission. In particular, the non-thermal nature and the softness of the observed spectrum are unresolved issues. To tackle these we perform Monte Carlo simulations of radiation-matter interactions in a scattering dominated photon-lepton plasma. In our model, the plasma (initially in equilibrium) is driven out of equilibrium by energy injection mimicking the effect of energy dissipation via shocks or magnetic reconnection. We show how equilibrium restoration leads to transient yet observable non-thermal features such as power-law tails, high energy bumps etc. On comparing our synthetic spectra with observations (Band Spectrum) we predict spectral correlations and conclude why photon-rich plasmas are a better GRB plasma candidate than pair-enriched plasmas.

The Formation of Stardust: Astrophysics by way of Quantum Chemistry (Christopher Mauney)

Cosmic dust was long considered a triviality by theorists and a nuisance by observers. However, as is a common theme in the field of physics, what was once mundane is discovered to be a rich source of insight, knowledge, and mystery. Dust, the molecular grains that form in the cooling expansion of stellar winds and supernova remnants, plays a key role in planetary, stellar, and galactic evolution. Earth, it’s life, our very selves are the result of the dust from generations of dead stars. Clearly, and understanding of dust formation and its evolution through the galaxy is not only an interesting task, but a vital one. Much research in recent years has unlocked many key answers. However, questions remain. One difficult, but immediate question in particular, which has repercussions throughout astrophysics: What is the main source of dust in the galaxy? Our work focuses on contributing to the answer of this question. We begin by scaling down to the grains themselves, using modern quantum methods to determine grain properties. This data is used to refine and update current dust formation (or nucleation) models, offering a more accurate model of the creation of dust grains in astrophysical environments.