Bulletin of the American Physical Society
Joint Fall 2021 Meeting of the Texas Sections of APS, AAPT, and SPS
Volume 66, Number 10
Thursday–Saturday, October 21–23, 2021; Houston; Central Time
Session M05: Astrophysics and Space Science I |
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Chair: Stephanie Ingle, Lee College Room: STEM 3133 |
Friday, October 22, 2021 2:00PM - 2:12PM |
M05.00001: An Invariant Characterization of the Levi-Civita Spacetimes Cooper Watson, William Julius, Matthew Gorban, David McNutt, Eric Davis, Gerald Cleaver In the years 1917--1919 Tullio Levi-Civita published a number of papers presenting new solutions to Einstein's equations. This work, while partially translated, remains largely inaccessible to English speaking researchers. In this paper we review these solutions, and present them in a modern readable manner. We will also compute both Cartan--Karlhede and Carminati--Mclenaghan invariants such that these solutions are invariantly characterized by two distinct methods. These methods will allow for these solutions to be totally and invariantly characterized. Because of the variety of solutions considered here, this paper will also be a useful reference for those seeking to learn to apply the Cartan--Karlhede algorithm in practice. [Preview Abstract] |
Friday, October 22, 2021 2:12PM - 2:24PM |
M05.00002: Extension of local spiral structure based on massive OB-stars to Gaia EDR3 William Chisholm, Louis Strigari Gaia Early Data Release 3 provides precise parallaxes for a large sample of massive OB-stars. This precise astrometry allows for an investigation of local Milky Way spiral structure. We use a compiled list of OB-stars in the local galactic arms containing astrometric solutions derived from Gaia DR2, and we crossmatch given Gaia DR2 sources to find Gaia EDR3 counterparts. Additionally, a crossmatch with Hipparcos was performed. We have compiled a list of ~250 O-type sources and ∼4,000 B-type sources with 5D astrometric solutions. The improvements on the accuracies of these sources substantiate previous analysis of local spiral structure. [Preview Abstract] |
Friday, October 22, 2021 2:24PM - 2:36PM |
M05.00003: Relic abundance of a new dark matter WIMP annihilating to WW* and ZZ* Caden LaFontaine, Bailey Tallman, Sabrina Hernandez, Diego Cristancho Guerrero, Spencer Ellis, Trevor Croteau, Brandon Torres, Roland Allen We report calculations of the annihilation cross-section for the dark matter WIMP that we have proposed, here represented by H. For annihilation to real particles, WW and ZZ, we make the approximation that the W, Z, and H masses are nearly equal. We find that the total annihilation cross-section is more than an order of magnitude too large for $m_Z > m_H > m_W$, and about a factor of 2 larger still for $m_H > m_Z$. (Without this approximation, the cross-sections would be even larger.) For annihilation to one real particle and one virtual, WW* and ZZ*, we make the approximation of neglecting the masses of the fermions (which are all relatively small). If $m_H$ is well below $m_W$, the total cross-section is more than an order of magnitude too small. As the H mass approaches $m_W$ from below, however, there is resonant behavior involving the W propagator, and for a mass of about 72 GeV the cross-section has the value corresponding to the observed relic abundance. This annihilation cross-section is consistent with the limits set by observation of gamma-ray emissions from dwarf spheroidal galaxies by Fermi-LAT, and with gamma-ray emissions from the Galactic center that have been interpreted as possible evidence of dark matter annihilation. [Preview Abstract] |
Friday, October 22, 2021 2:36PM - 2:48PM |
M05.00004: Fermi-LAT gamma-ray observations -- potential support for a multicomponent dark matter scenario Bailey Tallman, Caden LaFontaine, Diego Cristancho Guerrero, Sabrina Hernandez, Trevor Croteau, Brandon Torres, Spencer Ellis, Roland Allen There is tension between observations of gamma-ray emission from dwarf spheroidal galaxies, and other sources, and the most natural supersymmetric dark matter candidates. On the other hand, several independent analyses suggest that the observed emissions of gamma rays from the Galactic center are consistent with annihilation of dark matter particles of some kind, with masses somewhat below 100 GeV [1-4]. We will describe a multicomponent dark matter scenario with a subdominant neutralino and a dominant higgson [5] of mass $\sim 72$ GeV which is fully consistent with experiment and observation. [1] Lisa Goodenough and Dan Hooper, arXiv:0910.2998 [hep-ph]. [2] Vincenzo Vitale and Aldo Morselli (for the Fermi/LAT Collaboration), arXiv:0912.3828 [astro-ph.HE]. [3] Christopher Karwin, Simona Murgia, Tim M. P. Tait, Troy A. Porter, and Philip Tanedo, Phys. Rev. D 95, 103005 (2017), arXiv 1612.05687 [hep-ph]. [4] Rebecca K. Leane and Tracy R. Slatyer, Phys. Rev. Lett. 123, 241101 (2019), arXiv:1904.08430 [astro-ph.HE]. [5] Caden LaFontaine, Bailey Tallman, Spencer Ellis, Trevor Croteau, Brandon Torres, Sabrina Hernandez, Diego Cristancho Guerrero, Jessica Jaksik, Drue Lubanski, and Roland Allen, Universe 7, 270 (2021), arXiv:2107.14390 [hep-ph], and references therein. [Preview Abstract] |
Friday, October 22, 2021 2:48PM - 3:00PM |
M05.00005: The relic abundance of dark matter -- a nontrivial physics and mathematics problem Trevor Croteau, Spencer Ellis, Brandon Torres, Sabrina Hernandez, Diego Cristancho Guerrero, Bailey Tallman, Caden LaFontaine, Roland Allen A vast number of dark matter candidates have been proposed, but almost none of them have provided a well-defined and natural explanation of the observed abundance of dark matter. We will discuss the following aspects of this problem: (1) The ''WIMP miracle'': A weakly interacting massive particle can have very roughly the observed abundance if its mass is $\sim 100$ GeV and the interactions responsible for annihilation in the early universe are not too strong (or too weak). (2) A nonlinear Boltzmann equation can be derived that yields the relic abundance in the present universe, but this equation is quite nontrivial to solve. One approach will be described. (3) The cross-section for annihilation has been found to be too large for the most natural dark matter candidate of supersymmetry, a relatively light neutralino, making the relic density too small by about an order of magnitude. (4) We propose a candidate, resulting from an extended Higgs sector, that will yield the observed abundance with a particle mass of about 72 GeV, as described in two other talks at this conference. [Preview Abstract] |
Friday, October 22, 2021 3:00PM - 3:12PM |
M05.00006: Probing the outermost radii of classical dSphs with Gaia EDR3 Yuewen Qi, Paul Zivick, Andrew Pace, Alexander Riley, Louis Strigari We use Gaia EDR3 data to identify stars associated with six classical dwarf spheroidals (Draco, Ursa Minor, Sextans, Carina, Fornax, Sculptor) at their outermost radii, beyond their tidal limits. For four of the star candidates selected from EDR3 astrometry (two in Sextans, one in Sculptor, and one in Draco) we find radial velocity matches, indicating that these stars are associated with their respective dwarf spheroidals (dSphs) at high probability, even though they reside beyond the King tidal limit. Many of our candidates, including stars with radial velocity confirmation, lie along the orbital track of the satellites. Follow-up spectra on all of our candidates, including possible metallicity information, will help confirm their association with their respective dSphs, and could represent the first evidence for extended stellar halos or tidal debris around these classical dSphs. [Preview Abstract] |
Friday, October 22, 2021 3:12PM - 3:24PM |
M05.00007: Two regimes of tidal-stream circularization by supermassive black holes Michael Kesden, Joseph Rossi, Juan Servin Stars that approach a supermassive black hole (SMBH) too closely can be disrupted by the tidal gravitational field of the SMBH. The resulting debris forms a tidal stream orbiting the SMBH which can collide with itself due to relativistic apsidal precession. These self-collisions dissipate energy, causing the stream to circularize. We perform kinematic simulations of these stream self-collisions to estimate the efficiency of this circularization as a function of SMBH mass $M_\bullet$ and penetration factor $\beta$, the ratio of the tidal radius to the pericenter distance. We uncover two distinct regimes depending on whether the time $t_c$ at which the most tightly bound debris circularizes is greater or less than the time $t_{\rm fb}$ at which the mass fallback rate peaks. The bolometric light curve of energy dissipated in the stream self-collisions has a single peak at $t > t_{\rm fb}$ in the slow circularization regime ($t_c > t_{\rm fb}$), but two peaks (one at $t < t_{\rm fb}$ and a second at $t_{\rm fb}$) in the fast circularization regime ($t_c < t_{\rm fb}$). Tidal streams will circularize in the slow (fast) regime for apsidal precession angles less (greater) than 0.2 radians which occur for $\beta < (>) (M_\bullet/10^6M_\odot)^{-2/3}$. [Preview Abstract] |
Friday, October 22, 2021 3:24PM - 3:36PM |
M05.00008: A Simple Experiment Testing Quantum Mechanics and Gravity Louise Riofrio, Heather Sartain Quantum Astrobiology Center along with University of Houston and another Texas university will perform a novel experiment testing Planck masses and gravity. This research began with cosmology, an expanding Universe of scale R = ct, where c is speed of light and t is age of Universe. Gravity would then cause expansion to slow over time. The surprising prediction of the speed of light varying by 0.72 cm/sec/yr has been verified by data from our Lunar Laser Ranging Experiment, and may be further tested by the Atomic Clock Ensemble in Space aboard ISS. In Planck units two equations combine as M = R = t, suggesting that these tiny units are fundamental. The Planck mass is an observable quantity similar to a flea’s egg. We place two spherical masses on a level low-friction surface, grounded within a vacuum chamber, and observe for gravitational attraction. A negative result suggests that gravitational mass is quantized at the Planck scale. Quantum mechanics has applications for astrobiology and living cells, explaining why most cells are limited by the Planck mass. This continuing research may connect cosmology of the large Universe with the microscopic world. [Preview Abstract] |
Friday, October 22, 2021 3:36PM - 3:48PM |
M05.00009: Almost-Ideal Filtering: A Demonstration of New Signal Processing Tools in GW150914, The First Observation of Gravitational Waves Caleb Broodo, Gemunu Gunaratne aLIGO (The Advanced Laser Interferometer Gravitational-Wave Observatory) was designed to search for gravitational waves, opening up a new era of astronomy. As notably sensitive instruments (able to detect distortions of $10^{-18}$ m), the detectors are subjected to various vibrations caused by microseismic waves and anthropogenic sources (traffic, construction, etc.). This noise can drown out the minor astrophysical signals possibly embedded in the observation. It is therefore necessary to conduct careful signal processing in order to establish the presence of gravitational waves. In this presentation, we explore minor ways to improve techniques used in aLIGO’s matched-filtering analysis. We present a novel approach: adjusting Welch's method by replacing the default periodizing Hann window with a recently developed “kDAF” window. The kDAF window has a flat top with smooth roll-off, allowing it to consolidate lost information unaccounted for by the Hann window. This window exchange expects to improve the matched-filtering calculation by providing a better estimate to the detectors’ noise. A full demonstration of this approach has been done using aLIGO network data from the first confirmed BBH event GW150914, observed in 2015. More events will be pursued in future studies. [Preview Abstract] |
Friday, October 22, 2021 3:48PM - 4:00PM |
M05.00010: Will the black hole still collapse? Han Yong Quan The density of black holes is so huge that light cannot escape. Does nature have "matter" that is denser than black holes? exist! The black hole will also collapse and become a denser "matter" than the black hole. My theory of calculating the density of black holes at the 2021 spring meeting of the American Physical Society believed that the linear velocity at the edge of the black hole is the speed of light. If the black hole collapses again, the density will inevitably be greater, and its linear speed of rotation will inevitably exceed the speed of light. This "matter" is even darker than the black hole, and may be the dark matter that scientists are looking for. This theory provides new ideas for the exploration of the origin of the universe, because the observational facts now believe that the beginning of the universe was faster than light. [Preview Abstract] |
Friday, October 22, 2021 4:00PM - 4:12PM |
M05.00011: Lightcurves and Rotational Periods of Five Main Belt Asteroids Harum Ahmed, Kent Montgomery, Michael Cheek The lightcurves and rotational periods for five main belt asteroids: 3942 Churivannia: 2.516 \textpm 0.002 hours, 4673 Bortle: 2.643 \textpm 0.001 hours, 5186 Donalu: 3.154 \textpm 0.001 hours, 8441 Lapponica: 3.285 \textpm 0.001 hours, and 12259 Szukalski: 5.986 \textpm 0.001 hours are presented in this research. The rotational period of 3942 Churivannia and 12259 Szukalski were determined for the first time and the other three asteroids, 4673 Bortle, 5186 Donalu, and 8441 Lapponica, were observed to improve their previously established periods. The asteroid's apparent magnitude, declination, and opposition date were the criterion used to choose these asteroids. The lightcurves were plotted using photometric data taken over the course of several nights using two telescopes, one was the Texas A{\&}M University-Commerce 0.7-m telescope and the other was the SARA-CT 0.6-m telescope. The photometric data was calibrated, reduced and aligned using different softwares and the average difference in mag. between five comparison stars and each asteroid was found for each image and then plotted versus time, producing a lightcurve. The lightcurves were then analyzed to determine the shape and rotational period of each asteroid. [Preview Abstract] |
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