Bulletin of the American Physical Society
86th Annual Meeting of the APS Southeastern Section
Volume 64, Number 19
Thursday–Saturday, November 7–9, 2019; Wrightsville Beach, North Carolina
Session G04: Cosmology, Astrophysics and Gravitation |
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Chair: Cori Fletcher, Universities Space Research Association Room: Holiday Inn Resort Oceanwatch |
Friday, November 8, 2019 2:00PM - 2:12PM |
G04.00001: Gamma ray burst contributions from natural nuclear criticality events Robert Hayes The energy spectra from the rising and trailing edges of fast rise exponential decay (FRED) gamma ray bursts (GRB) along with the time dependence of its exponential decay is shown to be effectively identical to that from terrestrial pulsed criticality events. This is argued to occur in a similar fashion as that of the Oklo event (Krane 1988). The Oklo natural nuclear reactor from Gabon Africa went critical around a billion years ago having at that time enriched uranium present due to reverse radioactive decay of the shorter half-life fissile isotope $^{\mathrm{235}}$U. The same event which gave rise to Oklo (and the tightest constraints on the fine structure constant) are argued to still be present in the interstellar media providing new criticality events in accretion disks. These would pulse as they become critical, thermally expand driving them subcritical and then coalescing again by gravity into a critical accretion disk sectional mass giving rise to pulsing. In this sense, it has been shown that all the major features seen in FRED GRB can be explained by criticality events comparable to the Oklo event (Hayes 2013). Source terms from neutron star mergers are then considered in terms of potential contributors including long lived isotopic abundances. References: Hayes R. B (2013) Nuclear criticality as a contributor to gamma ray burst events. Astrophys. Space Sci. 345, 147-154. Krane K (1988) Introductory Nuclear Physics; John Wiley and Sons; ISBN 978-0471805533 [Preview Abstract] |
(Author Not Attending)
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G04.00002: Variable Nature of Accretion-Disk Wind Structure in NGC 3783 Mary Ogborn, Keigo Fukumura Seyfert galaxies are a sub-class of active galactic nuclei (AGNs) that are bright sources of UV and X-Rays in which outflows are ubiquitously observed and are thought to be produced from accretion disks around supermassive black holes (SMBHs). These ionized outflows manifest themselves as blueshifted absorption features in X-ray (aka. warm absorbers), allowing for spectroscopic analysis to learn more about the physical conditions of the plasma as well as the AGN itself. NGC 3783 is a Type 1 Seyfert galaxy at redshift z=0.00976 hosting a SMBH of 3e7 solar-masses. By using multi-epoch data obtained with Chandra X-Ray Observatory’s High Energy Transmission Grating Spectrometer (HETGS), we analyze the archival HETGS data and model the detected warm absorbers based on the magnetically driven disk-wind scenario by the action of a global magnetic field. The proposed study constrains two primary model parameters: wind density and the inclination angle for a given density slope that also help determine the warm absorber’s property (e.g. velocity, column density, ionization state and distance). Our goal is to determine the physical conditions of the observed warm absorbers in each epoch for NGC 3783 and further explore its potential time variability over multiple epochs. [Preview Abstract] |
Friday, November 8, 2019 2:24PM - 2:36PM |
G04.00003: Analysis of X-Class Solar Flares in the AIA 131A Channel Alya Sharbaugh, Amy Winebarger, Mary Kidd This project represents a small part of the general study by NASA's Marshall Space Flight Center into how the evolution of high temperature plasma is dependent upon the morphology of solar flares. Data for this analysis was provided by the Solar Dynamics Observatory (SDO), a NASA satellite launched in 2011 as part of the Living With a Star initiative. The SDO carries an instrument called the Atmospheric Imaging Assembly (AIA) which uses Fe V, XX, and XXIII to focus on flaring regions of the Sun. This presentation will detail the process of filtering usable satellite data using SunPy, modeling different parameters of solar flares, and mapping images of flares to create movies. [Preview Abstract] |
Friday, November 8, 2019 2:36PM - 2:48PM |
G04.00004: Developing a Laboratory-scale Kilonova Apparatus Martin Driggers, Matt Meyers, Patrick Johnson, Chad Sosolik Kilonova are currently the predicted source of all elements heavier than iron. Following the recent measurement of light from a kilonova event, emissions spectra from these heavier elements is necessary to verify this theory. We have designed and built an apparatus capable of creating heavy metal ions that emit spectra relevant to kilonova events. This apparatus consists of a vacuum chamber containing a tunable RHEED electron gun and a metal target. The electron gun bombards the target producing ions. The target consists of a box with an entrance port for the electrons and a viewing port to observe the spectra. To test our apparatus, we measured the ion current produced from a copper target. We also captured long exposure images of the target and found that the beam does produce visible light. While we have so far been unable to verify the copper spectra produced, we are modifying our apparatus with a higher-current electron gun to produce higher-intensity spectra for this experiment. [Preview Abstract] |
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