Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session B04: Cecilia Payne-Gaposchkin Thesis Award Finalist SessionInvited
|
Hide Abstracts |
Sponsoring Units: DAP Chair: Loverde Marilena, Stony Brook University Room: Sheraton Plaza F |
Saturday, April 13, 2019 10:45AM - 11:21AM |
B04.00001: MHD turbulence: resolving astrophysical puzzles Invited Speaker: Siyao Xu Turbulence and magnetic fields are ubiquitous in the Universe. Their importance to astronomy cannot be overestimated. Constructing predictive theories of the magnetic field generation by turbulence, the dissipation of MHD turbulence, and the interaction of energetic particles and magnetized turbulence are at the core of my thesis. These fundamental non-linear processes are usually addressed numerically. My thesis work provided analytical predictions, which either have been confirmed by numerical simulations or are in physical regimes beyond current computational power. In my talk, I will present some examples for the application of my theories in resolving diverse long-standing astrophysical puzzles, and in particular, a new mechanism of particle acceleration in high-energy astrophysical environments such as Gamma-Ray Bursts. |
Saturday, April 13, 2019 11:21AM - 11:57AM |
B04.00002: Signatures of the First Stars in Relics of the First Galaxies Invited Speaker: Alexander Ji In the billion years after the big bang, the first stars and galaxies polluted the universe with the first heavy elements and produced high energy photons that reionized the intergalactic medium. Understanding this early era is at the frontier of modern astrophysics and cosmology, but direct observations are challenging. An alternate approach is to study the old dwarf galaxies that orbit our Milky Way galaxy today, which descended from the first galaxies and contain stars that retain a record of their past. I will first explore theoretical models to interpret the chemical signatures preserved in these relic stars, tracing them to their present day locations in the Milky Way. I then use high-resolution spectroscopy to measure the chemical abundances of stars in three ultra-faint dwarf galaxies. The key result is a serendipitous discovery with important implications for the origin of the elements. Stars in the galaxy Reticulum II display extremely enhanced r-process abundances 2-3 orders of magnitude higher than in other ultra-faint dwarf galaxies. The neutron-capture material in Reticulum II was thus synthesized in a single prolific event, likely a neutron star binary merger, addressing a 60-year-old question about the astrophysical origin of r-process elements. |
Saturday, April 13, 2019 11:57AM - 12:33PM |
B04.00003: Hunting for the Heaviest Elements with Multi-Messenger Astronomy Invited Speaker: Jennifer Barnes The merger of a neutron star with a second neutron star or a black hole produces a quasi-thermal transient powered by the radioactive decay of unstable nuclei assembled during the merger by rapid neutron capture (the r-process). This emission, called a kilonova, is a promising electromagnetic (EM) counterpart to the gravitational wave signals produced by such mergers. Observations of kilonovae allow the determination of the mass and composition of the material ejected by a merger, which is important for constraining the neutron star equation of state and understanding the astrophysical origin of r-process elements. However, interpreting observations requires robust models of kilonova emission, and the construction of such models is challenging due to the complexity of the r-process and the lack of relevant experimental data. I will present theoretical work that enabled the development of detailed and accurate kilonova models. I will discuss the optical properties of r-process material, and show how theoretically-derived synthetic r-process opacities changed our expectation of kilonova colors, provided a tool to differentiate light from heavy regimes of r-process nucleosynthesis, and facilitated the development of multi-component kilonova models. Next, I will show how modeling the transport of radioactive decay products in the kilonova ejecta improved predictions of kilonova light curves and established a connection between bolometric luminosity and the details of r-process radioactive decay. Finally, I will review the role of these models in the interpretation of the EM emission from the first detected neutron star merger, GW170817. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700