Long duration solar gamma ray flares
Lisa Winter, LANL
Long duration solar gamma ray flares (LDGRFs) present a challenge to models of solar flares. While the gamma ray emission initially was thought to be the high energy extension of emission produced at the footprints of flare loops, LDGRFs are more energetic than expectations and last hours after the X-ray emission subsides. Evidence of gamma ray emission from flares on the backside of the Sun prompted the idea that LDGRFs instead are created from acceleration of particles in the shock waves of coronal mass ejections (CMEs). To determine which of these scenarios is more likely, we conducted a study of the flare and CME properties for LDGRFs detected by the Fermi Gamma-Ray Observatory. We also performed a reverse association analysis to determine which flares and CMEs do not produce gamma-ray emission. In this talk, these results are presented, showing that LDGRFs are most likely associated with CME acceleration.
Asteroseismology of Red Giants: The Detailed Modeling of Red Giants in Eclipsing Binary Systems
Jean McKeever, NMSU
Asteroseismology is an invaluable tool that allows one to peer into the inside of a star and know its fundamental stellar properties with relative ease. There has been much exploration of solar-like oscillations within red giants with recent advances in technology, leading to new innovations in observing. The Kepler mission, with its 4-year observations of a single patch of sky, has opened the floodgates on asteroseismic studies. Binary star systems are also an invaluable tool for their ability to provide independent constraints on fundamental stellar parameters such as mass and radius. The asteroseismic scaling laws link observables in the light curves of stars to the physical parameters in the star, providing a unique tool to study large populations of stars quite easily. In this work we present our 4-year radial velocity observing program to provide accurate dynamical masses for 16 red giants in eclipsing binary systems. From this we find that asteroseismology overestimates the mass and radius of red giants by 15% and 5% respectively. We further attempt to model the pulsations of a few of these stars using stellar evolution and oscillation codes. The goal is to determine which masses are correct and if there is a physical cause for the discrepancy in asteroseismic masses. We find there are many challenges to modeling evolved stars such as red giants and we address a few of the major concerns. These systems are some of the best studied systems to date and further exploration of their asteroseismic mysteries is inevitable.