Bulletin of the American Physical Society
Mid-Atlantic Section Meeting 2021
Volume 66, Number 18
Friday–Sunday, December 3–5, 2021; Rutgers University, New Brunswick, New Jersey
Session E03: Astrophysics IV |
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Chair: Richard Miller, Johns Hopkins Applied Physics Laboratory Room: 202A |
Saturday, December 4, 2021 2:00PM - 2:36PM |
E03.00001: Time Variations of GeV-range Cosmic Rays Invited Speaker: Pierre-Simon Mangeard Time variations of the flux of low-energy (GeV-range) cosmic rays are observed at Earth. On one hand, the flux of Galactic cosmic rays is modulated by the long term magnetic activity of the Sun (11- and 22-year solar cycle). On the other hand, the propagation of transient solar activities in the local space environment disrupts the flux of cosmic rays impinging Earth with a time scale from seconds to weeks (Forbush decreases, Solar Energetic Particles). For about six decades, ground-based neutron monitors have been the premier instruments to measure the time variations of the cosmic rays and provide an unique insight of the Sun's influence on Earth. The United States, which owns and operates ten neutron monitor stations (newly called the Simpson Neutron Monitor Network), is one of the main data providers to the worldwide neutron monitor network. At the dawn of the new solar cycle, I present the status of the neutron monitor network, its key role, alongside space instruments such as AMS-02, to measure the future time variations of the cosmic rays. I discuss recent developments of the neutron monitor observations based on details of the timing distributions of the neutron detections that extend the reach in energy of the neutron monitor network. Finally, preliminary results of the large solar event observed on October 28$^{\mathrm{th}}$, 2021 are presented. [Preview Abstract] |
Saturday, December 4, 2021 2:36PM - 2:48PM |
E03.00002: Analyzing Cosmic Ray Elemental Spectra Yuca Chen, Eun-Suk Seo Various balloon-borne and space-based experiments have provided direct measurements of cosmic-ray elemental spectra for a wide energy range. Compiled for an element range from $\textrm{ Z } = 1 \textrm{ to } 14$ over an energy range of ${\sim 2} \textrm{ - } {2 \times 10^5}$ GeV/n, the data were fit with a simple power-law $F = CE^{-\gamma}$ over small energy intervals. To examine the energy dependence of the individual fluxes of each element, detailed variations of the spectral indices were obtained as a function of energy in a model-independent way. Elements are classified into groups based on their energy-dependent behavior. Differences among groups will be presented and their implications will be discussed. [Preview Abstract] |
Saturday, December 4, 2021 2:48PM - 3:00PM |
E03.00003: A Leptohadronic Particle Transport Model for 3C 454.3 Tiffany Lewis A blazar is a galaxy whose central supermassive black hole is accreting so much material so quickly, that it launches and sustains a massive, powerful jet that happens to be pointed at Earth. The beamed emission from this kind of jet makes blazars the most numerous extragalactic source in X-rays and gamma-rays. In November 2010, one particular blazar, 3C 454.3 was observed across the electromagnetic spectrum while experiencing an unusually bright flare. To study the acceleration of particles in such an event, we create a numerical model of the particle population, accounting for each physical process affecting particle energetics. Here, we develop and apply a new particle transport model, co-solving the electron and proton Fokker-Planck equations. Each equation treats relevant particle acceleration and cooling terms, within a single homogeneous zone near the base of the blazar jet. Both leptonic and leptohadronic models represent the data well. Upcoming observations of high-energy polarization, from AMEGO/AMEGO-X may help to distinguish between the models. [Preview Abstract] |
Saturday, December 4, 2021 3:00PM - 3:12PM |
E03.00004: High Precision Ringdown Modeling: Multimode Fits and BMS Frames Neev Khera, Lorena Magana Zertuche, Keefe Mitman, Leo Stein, Michael Boyle, Nils Deppe, Nils Fischer, Francois Herbert, Dante Iozzo, Lawrence Kidder, Jordan Moxon, Harald Pfeiffer, Mark Scheel, Saul Teukolsky, William Throwe Quasi-normal mode (QNM) modeling is an invaluable tool for studying strong gravity, characterizing remnant black holes, and testing general relativity. To date, most studies have focused on the dominant $(2,2)$ mode. But, as gravitational wave observatories become more sensitive, they can resolve higher-order modes. Multimode fits will be critically important, and in turn require a more thorough treatment of the asymptotic frame at null infinity. We present a technique to systematically fit a QNM model containing many modes, and also illustrate the importance of mapping the numerical waveforms to the correct Bondi-Metzner-Sachs frame of numerical simulations to obtain high accuracy. [Preview Abstract] |
Saturday, December 4, 2021 3:12PM - 3:24PM |
E03.00005: Correcting stellar activity from radial velocity measurements using frequency domain linear regression in exoplanet searches Victor Ramirez Delgado, Joan Caicedo Vivas, Sarah Dodson-Robinson High precision radial velocity (RV) measurements have created the need for better diagnostics of stellar activity in exoplanet detection. Stellar surface activity produces periodic and quasiperiodic signals such as rotation, and oscillations that can mimic or hide a real planet RV signal. We introduce a new computational method of correcting for stellar activity, by using data from indicators, such as H$\alpha $ and S-index, that trace the activity from the surface of stars. Our algorithm performs Fast Fourier Transforms (FFT) on time series of RVs and activity indicators to analyze periodic signals from a target star. These manifest as peaks centered at different frequencies. To model the activity present in the RV, multiple linear regression is computed, using the indicator's FFTs as the explanatory variables, to predict the RV FFT. Our activity model is then transformed into the time domain and subtracted from the original RVs, and thereby obtain the residuals. Applying our method to the data set of CoRoT-7 (Queloz et. al (2009))(Haywood et. al (2014)), results in a significant power reduction in the peak coming from the star's rotation period. The peak associated with the period of planet c remains unaffected, providing promising results for the analysis efficacy. [Preview Abstract] |
Saturday, December 4, 2021 3:24PM - 3:36PM |
E03.00006: Exotic Compact Objects: The Dark White Dwarf Michael Ryan, David Radice, Sarah Shandera Dissipative dark matter models provide a solution to the dark matter problem while opening up the possibility for exotic compact object formation. These objects, ranging from dark black holes down to dark white dwarfs, have the potential for unique characteristics that set them apart from their baryonic counterparts. Furthermore, gravitational wave observations of their mergers may provide the only direct window on a potentially entirely hidden sector. We present here an introduction to dark white dwarfs, with a focus on how dark microphysics drive macroscopic characteristics distinct from astrophysical compact objects. We also discuss some implications for gravitational wave observations, further highlighting the need for third generation detectors. [Preview Abstract] |
Saturday, December 4, 2021 3:36PM - 3:48PM |
E03.00007: New Calculation of Gravity Frequency in Solar Systems Gh. Saleh It is clear that all the stars and planets revolve in orbits around each other which there are Gravitational Force Lines (gravitational fluxes) between them, and the effect of these lines creates stability and balance among planets and stars. In fact, it can be said that the force related to kinetic energy of a planet is always in action with the gravity force lines and causes equilibrium, and the kinetic energy of the planets has been always equal to the energy of the gravitational waves. If there is any relation between gravity and electromagnetic force it must be in their energy too. So: $\frac{1}{2}mv^2$=$nh\vartheta{}$ , where “n” is the number of force lines passing through the surface of the planet. So we have: $n=\ \frac{S}{S_p}=\frac{4\pi{}r^2}{4\pi{}r_p^2}=\frac{r^2}{r_p^2}$ , where “S” is the planet area and “S$_{p}$” is the smallest possible area for a unit of electromagnetic wave (photon). Therefore: $\vartheta{}=\frac{r_p^2}{2h}\ \times{}\frac{mv^2}{r^2}$ . As: $\frac{r_p^2}{2h}=constant\cong{}\frac{1}{10}$ , so the gravitational frequency of the planet will be equal to: \[ \vartheta{}=\frac{mv^2}{10r^2}=\ \frac{E_k}{5r^2} \] where “E$_{k}$” is the kinetic energy of the planet and the speed of planets (v) is the effect of the central star force. [Preview Abstract] |
Saturday, December 4, 2021 3:48PM - 4:00PM |
E03.00008: The discovery of the characteristics of the energy of the universe and the conservation of mass and energy to analyze the changing laws of the universe Han Yong Quan The characteristic of cosmic energy is that it is an independent whole, without any matter and its effect, that is, potential energy cannot exist in the universe. The total energy of the universe can be expressed as E$=$1/2 (mv2). The starting state of my universe is that v tends to zero, m tends to infinity, and the density tends to infinity. E$=$m1c2. According to the meaning of Einstein's mass-energy equation, we know that m1 is the mass lost in the universe and c is the speed of light. When the lost mass of the universe is m1, the energy produced can accelerate the movement of all the remaining mass in the universe to the speed of light---transformed into photons and become a universe without static mass. At this time, the universe still only has kinetic energy, and there is no potential energy. The energy of the universe can also be used. Expressed as: E$=$1/2(m-m1)c2, then: 1/2(mv2)$=$1/2(m-m1)c2, the solution is: m1$=$m(1-v2/c2). When v1 approaches 0, the state of the beginning of the universe, that is, the big bang is about to begin, the universe begins to expand from rest, the mass gradually becomes smaller, the energy gradually becomes larger, and the mass and energy are conserved [Preview Abstract] |
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