Bulletin of the American Physical Society
Far West Section Fall 2022 Meeting
Volume 67, Number 10
Friday–Saturday, October 7–8, 2022; University of Hawaiʻi at Mānoa, Honolulu, HI
Session P01: Astrophysics |
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Chair: C. D. Hoyle, Cal Poly Humboldt Room: University of Hawai'i at Manoa, East-West Center Keoni |
Saturday, October 8, 2022 10:30AM - 10:42AM |
P01.00001: Approximate Bayesian Computation Applied to the Diffuse Gamma-Ray Sky Eric Baxter, Jacob Christy, Jason Kumar Many sources contribute to the diffuse gamma-ray background (DGRB), including star forming galaxies, active galactic nuclei, and cosmic ray interactions in the Milky Way. Exotic sources, such as dark matter annihilation, may also make some contribution. The photon counts-in-pixels distribution is a powerful tool for analyzing the DGRB and determining the relative contributions of different sources. Although informative, including photon energy information in a likelihood analysis of the counts-in-pixels distribution quickly becomes computationally intractable as the number of source types and energy bins increase. I will present how the likelihood-free method of Approximate Bayesian Computation (ABC) can be applied to the problem. I consider a mock analysis that includes contributions from dark matter annihilation in galactic subhalos as well as astrophysical backgrounds. I will show that the results acquired using ABC are consistent with the exact likelihood when energy information is discarded, and that significantly tighter parameter constraints can be obtained with ABC when energy information is included. Likelihood free methods such as ABC offer potent tools for analyzing the DGRB and understanding its varied origins. |
Saturday, October 8, 2022 10:42AM - 10:54AM |
P01.00002: Hard X-Ray View of Two Extreme Blazars Luana de Almeida Pacheco Utilizing the NuSTAR telescope, we study the hard x-ray spectrum of 1ES 0229+200 and H1426+428 using data collected during flaring and non-flaring periods. The data were cleaned and calibrated using NuSTARDAS software. Hard x-ray observations of similar sources have shown that the synchrotron radiation mirrors inverse Compton scattering, thus the study of high-energy x-rays can potentially provide more insight into the behavior of high-energy gamma-rays. We compare the observations of the flaring and non-flaring states, finding that for the two observations of H1426+428, the low state shows curvature, peaking at 10 kev, while the synchrotron emission of the high state peaks above 10 kev and shows no curvature. 1ES 0229+200, observed six times over two epochs, displays only marginal variability, with a spectrum that can be well described with a log-parabolic model, peaking beyond 10 keV. |
Saturday, October 8, 2022 10:54AM - 11:06AM |
P01.00003: Properties of Forbush Decreases observed with the AMS-02 daily proton flux Siqi Wang, Veronica Bindi, Cristina Consolandi, Claudio Corti, Christopher Light, Andrew Kuhlman A Forbush decrease (FD) is a sudden reduction of Galactic Cosmic Rays (GCRs), due to disturbances in the interplanetary magnetic field, usually caused by intense transient solar activities such as Interplanetary Coronal Mass Ejections (ICMEs) and Corotating Interaction Regions (CIRs). With the high-precision daily proton data measured by the Alpha Magnetic Spectrometer (AMS-02) on the International Space Station from May, 2011 to October, 2019, we identified more than one hundred FD events, with an automatic method. The properties of a selected set of ICME-caused and CIR-caused FD events were analyzed, using proton data with fine rigidity bins from 1 GV to 100 GV. The rigidity dependence of fluxes during FDs will be presented, separately for ICME and CIR FDs. The correlation between FD properties such as magnitude and maximum affected rigidity and synchronous solar wind parameters will also be presented, separately for ICME and CIR FDs. |
Saturday, October 8, 2022 11:06AM - 11:18AM |
P01.00004: The Development of Quicklook Software for the Prototype Schwarzschild-Couder Telescope Bryan Ochoa The Cherenkov Telescope Array (CTA) is an ongoing project to build the next generation ground-based gamma-ray observatory, which will serve as an open observatory to the astrophysics community. The U.S members of the CTA collaboration have pioneered the development of an innovative prototype Schwarzschild-Couder telescope (pSCT), which is based on a dual-mirror optical system. We are developing software which will allow for the gamma-ray events detected by the telescope to be displayed in nearly real time, which we refer to as Quicklook software. The telescope currently outputs its data in Flexible Image Transport System (FITS) file format, with only one server being able to access the data output. Our goal is to add the capability to access the data output with more than one server. We will share the status of our work on the Quicklook software, which will include a modification of the pSCT software to create many small FITS files which can be quickly calibrated for viewing, and later combined into a single large file. |
Saturday, October 8, 2022 11:18AM - 11:30AM |
P01.00005: Searching for velocity-dependent dark matter annihilation signals from extragalactic halos Aleczander Paul, Jason Kumar, Eric Baxter, Jack Runburg I consider gamma-ray signals of dark matter annihilation in extragalactic halos in the case where dark matter annihilates from a p-wave or d-wave state. In these cases, signals from extragalactic halos are enhanced relative to other targets, because the typical relative speed of the dark matter is larger in extragalactic halos. I perform a mock data analysis of gamma rays produced by dark matter annihilation in halos detected by the Sloan Digital Sky Survey. I find that searches of extragalactic halos with the current Fermi exposure can produce evidence for dark matter annihilation, though it is difficult to distinguish the p-wave and d-wave scenarios. With a factor 10x larger exposure, though, discrimination of the velocity-dependence is possible. |
Saturday, October 8, 2022 11:30AM - 11:42AM |
P01.00006: Bridging the Gap of Demographic Tension in Tidal Disruption Events Thomas Hong Tsun Wong, Lixin Jane Dai, Hugo Pfister Tidal disruption events (TDEs) are valuable probes of the demographics of supermassive black holes as well as the dynamics and population of stars in the centers of galaxies. We focused on studying how the debris disk formation and circularization processes can impact the possibility of observing prompt flares in TDEs. First, we investigate how the efficiency of disk formation is determined by the key parameters, namely, the black hole mass, the stellar mass, and the orbital penetration parameter that quantifies how close the disrupted star would orbit around the black hole. Then we calculate the intrinsic differential TDE rate as a function of these three parameters. Combining these two results, we find that the rates of TDEs with prompt disk formation are significantly suppressed around lighter black holes, which provides a plausible explanation for why the observed TDE host black hole mass distribution peaks around 106 solar masses. Therefore, the consideration of the disk formation efficiency is crucial for recovering the intrinsic black hole demographics from TDEs. |
Saturday, October 8, 2022 11:42AM - 11:54AM |
P01.00007: Estimating the Computational Requirements for the Large Data Output of the Prototype Schwarzschild-Couder Telescope Bryce Hoecker The prototype Schwarzschild-Couder Telescope (pSCT) is a dual mirror atmospheric gamma-ray telescope with a wide field of view and an increase in resolution/pixel count over current similar telescopes. The pSCT is being tested for possible inclusion in Cherenkov Telescope Array (CTA) Project, which is slated to be the largest and most sensitive gamma-ray observatory yet, with over a hundred telescopes in both the northern and southern hemisphere. A major hurdle in the development of the pSCT is how to process the large data stream that will be coming out of the telescope, as the number of pixels needed to be processed simultaneously is almost 10x other current telescopes. This data needs to be saved to a Flexible Image Transport System (FITS) file which can be hundreds or thousands of Gigabytes in size. On top of the large data stream, which will need large and powerful computers to process, we are tasked with implementing a quicklook or live-view imaging software. This work concentrates on utilizing the CFITSIO libraries provided by NASA and writing the code that will make this quicklook software be as fast as possible and take the least amount of computer resources possible, as current methods require a lot of processing time to compute the data. |
Saturday, October 8, 2022 11:54AM - 12:06PM |
P01.00008: Analysis of the blazar Markarian 421 with VERITAS Anthony Lazos Markarian 421 (Mrk 421) is a well observed and highly variable blazar: an active galactic nucleus (AGN) with its relativistic jet pointed at Earth. Observations of Mrk 421 at VERITAS (the Very Energetic Radiation Imaging Telescope Array System) began in 2007, and it has been observed almost nightly in the winter since 2018, weather permitting. We analyzed the most up to date dataset with the most recent instrument response functions, some of which we created specifically for this analysis, to create a light curve showing the measured flux each day as a function of time. We will present the Mrk 421 light curve and other results from this work. |
Saturday, October 8, 2022 12:06PM - 12:18PM |
P01.00009: Analysis of >100 GeV Gamma-Ray Data from Gamma-Ray Bursts Thura Dwe
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Saturday, October 8, 2022 12:18PM - 12:30PM |
P01.00010: High Energy Gamma-rays Jasmine s Asfour-palacios We study the emission mechanisms at work within very high-energy blazars by observing them when they are in a flaring state. For this to occur, it is necessary to be able to determine which sources are in active states. The space-based Fermi Large Area Telescope has a wide field of view, allowing it to efficiently monitor the sky for flaring blazars. Fermi is stationed in space to detect gamma rays directly whereas VERITAS, a ground-based gamma-ray observatory, detects gamma-ray-initiated showers from the ground. Our project seeks to create a trigger when a source is flaring in order to send an alert to the VERITAS team so they can direct the telescopes to observe the flare. Our mission is to focus on two state criteria to indicate a source is in a flaring state: the number of high-energy photons and the ratio of high-energy photons to low-energy photons. We aim to set thresholds that will allow telescopes such as VERITAS to trigger on approximately 10 total high states per year. |
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