Bulletin of the American Physical Society
APS April Meeting 2023
Volume 68, Number 6
Minneapolis, Minnesota (Apr 15-18)
Virtual (Apr 24-26); Time Zone: Central Time
Session F13: Transient & Time-Domain Astronomy |
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Sponsoring Units: DAP Chair: Margaret Millhouse, Georgia Institute of Technology Room: Marquette IV - 2nd Floor |
Sunday, April 16, 2023 8:30AM - 8:42AM |
F13.00001: Search for Gamma Ray Transient Activity with the HAWC Observatory at the locations of Fast Radio Bursts ELIJAH J Willox Over the past few years the number of known fast radio bursts (FRBs) has grown rapidly, yet we still don't have a clear picture of the progenitors of these events. Multiwavelength follow up of these transients will help constrain the available models for FRBs, and the HAWC Gamma-Ray Observatory has data covering a large number of FRBs. The HAWC data set contains contemporaneous observations of over 200 FRB events which was searched for short time scale gamma-ray emission. For each FRB, a time window of 100s before to 500s after the reported time were searched for bursts of 1 s, 5 s and 10 s duration. We then perform a simulation of the background at that location and distance over the same duration, and the two resulting distributions are compared to see the probability of a gamma-ray excess on any time window surrounding the FRB. The limits placed on the short timescale gamma-ray emission is also used to set an energy ratio of TeV gamma ray to radio detection which can be used to constrain models used to explain FRBs. |
Sunday, April 16, 2023 8:42AM - 8:54AM |
F13.00002: The IXPE view of GRB 221009A Michela Negro We present the IXPE observation of GRB~221009A which includes upper limits on the linear polarization degree of both prompt and afterglow emission in the soft X-ray energy band.GRB~221009A is an exceptionally bright gamma-ray burst (GRB) that reached Earth on 2022 October 9 after traveling through the dust of the Milky Way. The Imaging X-ray Polarimetry Explorer (IXPE) pointed at GRB~221009A on October 11 observing, for the first time, the 2--8 keV X-ray polarization of a GRB afterglow. Additionally, IXPE captured halo-rings of dust-scattered photons which are echoes of the GRB prompt emission, allowing for assessment on the prompt GRB emission. In this presentation we report the results of the IXPE observation of GRB 221009A. |
Sunday, April 16, 2023 8:54AM - 9:06AM |
F13.00003: An independent view of the z~5 star-forming galaxy population Huei M Sears Long gamma-ray bursts (GRBs) are created in the deaths of the most massive stars, and since massive stars do not live long, we know that they're created at the sites of recent star-formation and as such are created in star-forming galaxies. Current capabilities in observing star-forming galaxies at high redshift (z > 5) are limited in depth, but our ability to localize a GRB to its host galaxy is luminosity independent, and GRBs therefore are able to identify and probe low-luminosity star-forming galaxies that are often otherwise missed. In this project, I use rest-frame UV magnitudes of 23 GRB host galaxies at z~5 measured from new HST imaging to construct a UV luminosity function and measure a detection fraction (i.e. the fraction of those galaxies which are brighter than the detection limit of our imaging set up). By comparing these characterizations of this galaxy sample to those of star-forming galaxies, I answer the following questions: 1) What star-forming universe do GRBs trace? and 2) What does that traced universe tell us about star-formation? |
Sunday, April 16, 2023 9:06AM - 9:18AM |
F13.00004: Multi-scale Modeling of Gamma-ray Bursts Nicole M Lloyd-Ronning, Roseanne M Cheng, Lailani Kenoly, Ken Luu, Celia Toral
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Sunday, April 16, 2023 9:18AM - 9:30AM |
F13.00005: Particle Acceleration and Radiation Signatures from Relativistic Plasma Turbulence Luca Comisso Nature's most powerful high-energy sources are capable of accelerating particles to high energy and radiating it away on extremely short timescales, even shorter than the light crossing time of the system. It is yet unclear what physical processes can produce such an efficient acceleration, despite the copious radiative losses. By means of radiative particle-in-cell simulations, we show that magnetically dominated plasma turbulence generates a non-thermal particle spectrum with a hard power-law range (slope p∼1) within a few eddy turnover times. The particle spectrum becomes even harder (p |
Sunday, April 16, 2023 9:30AM - 9:42AM |
F13.00006: Simulated Kilonova Spectra Interpolation with Comparison to AT2017gfo Observations Marko Ristic, Richard O'Shaughnessy, V. Ashley Villar, Ryan Wollaeger, Oleg Korobkin, Chris L Fryer, Christopher J Fontes Neutron star mergers could be the primary channel for heavy-element nucleosynthesis in the Universe. Kilonovae provide, via observations of their spectra, a direct avenue to assess how much this channel contributes to r-process abundances. In this work, we present a simple kilonova spectral interpolation technique trained against our existing library of kilonova radiative transfer simulations which use state-of-the-art, physically-motivated atomic opacities and lines. Our model accurately reflects spectra for anisotropic (axisymmetric) time-dependent kilonova models over our presently four-dimensional kilonova model space. We compare our interpolated spectra to the AT2017gfo spectral data and find parameters consistent with our previous inferences deduced from long-term multiwavelength light curve observations. However, the spectral observations have significant systematic short-wavelength residuals relative to our models, which we cannot explain within our existing framework. Similar to previous studies, we argue an additional blue component is required. We find that a light, slow-moving lanthanide-free component could supplement early-time short-wavelength model deficits. |
Sunday, April 16, 2023 9:42AM - 9:54AM |
F13.00007: Signatures of heavy element nucleosynthesis in transients Nick Ekanger The astrophysical sources where heavy elements are synthesized are not fully understood and are windows into a rich array of high-energy astrophysics. We model and compare these astrophysical sources, such as the outflows of protomagnetars and compact object mergers, and make detailed predictions for the nucleosynthesis distributions from such sites. We also make estimates for the signatures of heavy element synthesis. We find that protomagnetars can synthesize moderately heavy nuclei and are compelling sources of ultra-high-energy cosmic rays after acceleration. We also find that compact object mergers, like binary neutron star and black hole-neutron star mergers, can undergo a robust r-process and source detectable kilonovae. |
Sunday, April 16, 2023 9:54AM - 10:06AM |
F13.00008: Detecting optical transients using artificial neural networks and reference images from different surveys Wendy Mendoza We present a technique to detect optical transients based on an artificial neural networks method. We describe the architecture of two networks capable of comparing images of the same part of the sky taken by different telescopes. One image corresponds to the epoch in which a potential transient could exist; the other is a reference image of an earlier epoch. We use data obtained by the Dr. Cristina V. Torres Memorial Astronomical Observatory and archival reference images from the Sloan Digital Sky Survey. We trained a convolutional neural network and a dense layer network on simulated source samples and then tested the trained networks on samples created from real image data. Autonomous detection methods replace the standard process of detecting transients, which is normally achieved by source extraction of a difference image followed by human inspection of the detected candidates. Replacing the human inspection component with an entirely autonomous method would allow for a rapid and automatic follow-up of interesting targets of opportunity. The toy-model pipeline we present here is not yet able to replace human inspection, but it might provide useful hints to identify potential candidates. The method will be further expanded and tested on telescopes participating in the Transient Optical Robotic Observatory of the South Collaboration. |
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