Bulletin of the American Physical Society
52nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 66, Number 6
Monday–Friday, May 31–June 4 2021; Virtual; Time Zone: Central Daylight Time, USA
Session C01: Atomic Physics and KilonovaeInvited Live
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Chair: Thad Walker, Wisconsin |
Tuesday, June 1, 2021 10:30AM - 11:00AM Live |
C01.00001: Neutron Star Mergers and Gravitational Waves: The Atomic Physics Connection Invited Speaker: Eve A Chase Neutron star mergers may reveal the cosmic origins of elements past the iron peak. During these highly energetic stellar mergers, neutron-rich material can assemble into heavy elements such as gold and uranium through rapid neutron capture (r-process) nucleosynthesis. The radioactive decay of these heavy elements powers a cascade of emission from gamma-rays to ultraviolet, optical, and infrared wavelengths, known as a kilonova. In this talk, I will present both the electromagnetic and gravitational-wave signatures of neutron star mergers, with a specific focus on rate estimates for current and upcoming gravitational-wave detectors, including the LIGO and Virgo interferometers. Additionally, I will describe efforts to constrain the cosmic origin of r-process elements through kilonova observations and motivate the essential role of atomic physics calculations in the process. |
Tuesday, June 1, 2021 11:00AM - 11:30AM Live |
C01.00002: Atomic Physics and the Spectral Modeling of Kilonovae Invited Speaker: Chris J Fontes Neutron star mergers are promising candidates for the observation of an electromagnetic (EM) signal coincident with gravitational waves. The 2017 observation of GW170817 [1] appears to be such an event, with gravitational waves confirmed by subsequent EM signals ranging from the infrared to x-ray portions of the spectrum. The atomic properties of the elements produced during these events are predicted to play an important role in the electromagnetic transients called kilonovae. Specfically, the radiative opacity plays an important role in determining the characteristics of the EM radiation that can penetrate the expanding media and ultimately be observed from Earth. The broad range of EM radiation observed from this recent event suggests that a significant fraction of the periodic table, from the fourth to seventh rows, is relevant. The presence of heavy r-process elements poses a particularly significant challenge to the accurate calculation of opacities and radiation transport, due to the appearance of dense forests of absorption lines arising from near-neutral lanthanide and actinide elements. We use the Los Alamos suite of atomic physics and plasma modeling codes [2] to investigate the use of detailed, fine-structure opacities [3-4] to model the EM emission from kilonovae. Our simulations [5-7] predict emission in a range of EM bands, depending on issues such as the presence of winds, elemental composition, and viewing angle. This talk emphasizes various atomic-physics aspects of the spectral modeling of neutron star mergers. |
Tuesday, June 1, 2021 11:30AM - 12:00PM Live |
C01.00003: The smoking gun of the r-process: first spectroscopic identification of the cosmic production site of r-process neutron capture Invited Speaker: Darach J Watson The rapid (r) neutron capture process that creates half of all the elements heavier than iron was first postulated six decades ago. But the event or events in which the r-process creates the heavy elements has only recently been confirmed spectroscopically. I present here the identification of the neutron-capture element strontium in the spectral series of the kilonova, AT2017gfo, emerging from the gravitational-wave–discovered neutron star merger, GW170817, the only kilonova where detailed spectra have so far been recorded. This identification of a neutron-capture element associated with the collision of two extreme-density stars firmly establishes the origin of r-process elements. |
Tuesday, June 1, 2021 12:00PM - 12:30PM Live |
C01.00004: Searching for High-Z Elements in Neutron Star Merger Ejecta Invited Speaker: Joan Marler Multi-messenger astronomy, in which gravitational wave detections are combined with subsequent measurements across the electromagnetic spectrum, provides new opportunities to study the physics in the extreme environments of neutron star mergers. Of particular interest is a deeper understanding of the heavy-element nucleosynthesis expected to occur in the ejecta from this neutron-rich environment, the so-called r-process. The laboratory spectroscopic data on the vast range of heavy elements (Rb-U), including the lanthanides and actinides, are so severely limited at present that emission models are only in qualitative agreement with the observed spectra. To partially alleviate this situation, a computational/experimental laboratory astrophysics collaboration between Clemson University, Auburn University, the University of Georgia, and Queen's University Belfast has been formed to generate reliable line lists for a range of r-process elements from neutral to triply charged. This talk will focus on experimental progress on investigations of the electronic structure of these elements using the Compact Toroidal Hybrid plasma experiment at Auburn University and CUEBIT (Clemson University Electron Beam Ion Trap). This work is done in collaboration with the groups of Brendan McLaughlin (QUB), Michael Fogle (AU) , Phillip Stancil (UGA), and Chad Sosolik (CU). |
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