Bulletin of the American Physical Society
2019 Joint Fall Meeting of the Texas Sections of APS, AAPT and Zone 13 of the SPS
Volume 64, Number 18
Friday–Saturday, October 25–26, 2019; Lubbock, Texas
Session H01: Astrophysics & Space Science |
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Chair: Joe Romano, Texas Tech University Room: Student Union Building Matador Room |
Saturday, October 26, 2019 10:06AM - 10:18AM |
H01.00001: What is the longest Gamma-Ray Burst that can be powered when a massive star collapses? Valeria U. Hurtado, Aldo Batta, Enrico Ramirez-Ruiz, Ariadna Murguia-Berthier, Nicole Lloyd-Ronning, Rosa Wallace Everson Gamma-Ray Bursts (GRBs) are the most powerful events in the Universe. They are bursts of gamma-rays lasting anywhere from less than a second to thousands of seconds, and are divided into different categories depending on the duration of their gamma-ray emission. Each duration class of GRB is hypothesized to come from a distinct progenitor - for example, GRBs lasting 10's of seconds are believed to come from the collapse of a massive star, while GRBs lasting less than a few seconds are believed to come from neutron star mergers. However, for Ultra-Long Gamma-Ray Bursts (ULGRBs) - GRBs lasting up to thousands of seconds, their progenitors are yet to be confirmed. We study one of the proposed models for ULGRBs: a massive evolved star that fails to go supernova after it collapses into a black hole. We tested our model using semi-analytic and numerical solutions with the hydrodynamical code MEZCAL. We show that the evolved stellar model is not suitable to explain ULGRBs after considering the contributions by the cocoon and feedback energies, which can unbind the stellar envelope on timescales shorter than the duration of ULGRBs. The analysis presented here provides constraints for the longest duration event that can be produced through this stellar collapse model. [Preview Abstract] |
Saturday, October 26, 2019 10:18AM - 10:30AM |
H01.00002: Multi-waveform cross-correlation search method for intermediate-duration gravitational waves from gamma-ray bursts Eric Sowell Gamma-ray Bursts (GRBs) are flashes of $\gamma$-rays thought to originate from rare forms of massive star collapse (long GRBs), or from mergers of compact binaries (short GRBs) containing at least one neutron star (NS). The nature of the post-explosion / post-merger remnant (NS versus black hole, BH) remains highly debated. In $\sim 50\%$ of both long and short GRBs, the temporal evolution of the X-ray afterglow that follows the flash of $\gamma$-rays is observed to ``plateau'' on timescales of $\sim 10^2-10^4$s since explosion, possibly signaling the presence of energy injection from a long-lived, highly magnetized NS (magnetar). The Cross-Correlation Algorithm (CoCoA) proposed by [R. Coyne et. al., Phys Rev D. {93} 104059 (2016)] aims to optimize searches for intermediate-duration ($10^2-10^4$s) gravitational waves (GWs) from GRB remnants. In this work, we test CoCoA on real data collected with ground-based GW detectors. We further develop the detection statistics on which CoCoA is based to allow for multi-waveform searches spanning a physically-motivated parameter space, so as to account for uncertainties in the physical properties of GRB remnants. [Preview Abstract] |
Saturday, October 26, 2019 10:30AM - 10:42AM |
H01.00003: Stream Evolution of Tidal Disruption Events of Main Sequence Stars by Supermassive Schwarzschild Black Holes Joe Rossi, Juan Servin, Michael Kesden When a star becomes close enough to a black hole that it falls within the tidal radius, the tidal gravitational field of the black hole is strong enough to rip the star apart. This forms a stream of debris which orbits and eventually circularizes about the black hole after relativistic precession causes the stream to collide with itself. It has been thought that the circularization process happens rather quickly. In this talk I will present a new model which shows that this might not be the case. Results will be presented outlining a lower limit for the time of the circularization process along with some of its other properties for various values of black hole mass and penetration factor, which defines the star’s angular momentum. [Preview Abstract] |
Saturday, October 26, 2019 10:42AM - 10:54AM |
H01.00004: Rates of Stellar Tidal Disruption Michael Kesden, Nicholas Stone, Eugene Vasiliev, Elena Rossi, Hagai Perets, Pau Amaro-Seoane Tidal disruption events occur rarely in any individual galaxy. Over the last decade, however, time-domain surveys have begun to accumulate statistical samples of these flares. What dynamical processes are responsible for feeding stars to supermassive black holes? At what rate are stars tidally disrupted in realistic galactic nuclei? What may we learn about supermassive black holes and broader astrophysical questions by estimating tidal disruption event rates from observational samples of flares? We address these questions in an upcoming review which summarizes current theoretical knowledge about rates of stellar tidal disruption, and compares theoretical predictions to the current state of observations. [Preview Abstract] |
Saturday, October 26, 2019 10:54AM - 11:06AM |
H01.00005: Isolated Binary Star Spin Evolution and its Implications for Binary Black Hole Precession Nathan Steinle, Michael Kesden A binary black hole (BBH) may astrophysically arise from isolated stellar binary evolution. The BBH spin momenta provide information on the specific formation history but are currently poorly constrained by observation. The important binary processes that determine the BBH progenitor spin evolution are tides, winds, common envelope (CE), supernova (SN) kicks and stellar core-envelope coupling. For a few physically motivated scenarios, we parameterize binary stellar evolution to study the relationship between these processes and the BBH properties. The O1 and O2 LIGO/Virgo sources have effective spin parameter $\chi_{\rm eff} \sim 0$ which is possibly explained by slow-spinning black hole progenitors due to strong stellar core-envelope coupling; however, if the coupling is weak then it can be explained by misalignments due to SN kicks. We identify likely precessing systems, i.e. for systems that primary SN occurs after a CE phase, binaries with initial mass ratio near unity, initial binary separations between $9000-12,000~R_{\odot}$, metallicity $Z \leq 0.1~Z_{\odot}$ and strong core-env. coupling or binaries with high initial progenitor spins, similar metallicity and weak core-env. coupling both produce maximally spinning black holes with appreciable misalignments. [Preview Abstract] |
Saturday, October 26, 2019 11:06AM - 11:18AM |
H01.00006: Search for R-modes from known Pulsar. Binod Rajbhandari, Benjamin Owen \textbf{gravitational waves are~ weak in signal but it can beat the spin down limits if observed for a longer time span. R-modes are the current quadruple oscillation of fluid in neutron star, which emits gravitational waves in 4/3 times the spin frequency in Newtonian case. We present here the first search of R-mode gravitational waves from known pulsar from a LIGO O1~ {\&} O2 run using the F-statistic method. We didn't find gravitational waves but set up a 95{\%} upper limit on amplitude strain.} [Preview Abstract] |
Saturday, October 26, 2019 11:18AM - 11:30AM |
H01.00007: Higher order equations to describe r-modes in Neutron Stars Giammarco Turriziani Colonna The structure and composition of Neutron Stars (NS) are unknown and the most promising way to understand them is through the Gravitational Waves (GW) asteroseismology, that is the study of the oscillations of the star through GWs. Between all the possible Quasi Normal Modes, the r-modes are the most promising source of GW because they can be unstable at an arbitrary angular velocity, due to the CFS instability mechanism. Other Quasi Normal Modes either are stable, which means that their amplitude are damped, or their instability turns on at very high angular velocities. This means that these other modes would be hardly detectable./ The frequencies of r-mode oscillations of rotating NS can be useful for guiding and interpreting GW and electromagnetic (EM) observations, which makes this study of relevance to both LIGO scientists, and astrophysicists. The frequencies of slowly rotating, barotropic and non magnetic Newtonian stars are well known, but subject to various corrections. The most important one is the relativistic correction, and the second most important is the rapid rotation correction. For this reason we decided to study the Lockitch-Andersson-Friedman (LAF) equations, that describe r-mode oscillations of stars in General Relativity (GR), and we aim to extend the [Preview Abstract] |
Saturday, October 26, 2019 11:30AM - 11:42AM |
H01.00008: Small-scale variabilities in the electric field and particle precipitation and their impacts on Joule heating Qingyu Zhu, Yue Deng, Astrid Maute, Authur Richmond In this study, the electric field and the particle precipitation at different spatial scale sizes have been investigated by utilizing the Dynamic Explorer 2 (DE-2) satellite dataset, focusing on conditions of moderately strong southward interplanetary magnetic field. DE-2 data have been binned over geomagnetic latitude and local time. It is found that, as compared with the large-scale average electric field and particle precipitation, the variabilities (i.e., departures from the large-scale average) of electric field and particle precipitation are not negligible. Moreover, the electric field variability tends to be anti-correlated with the particle precipitation variability in the auroral regions on small scale. The impacts associated with the small-scale electric field and particle precipitation variabilities on Joule heating have also been addressed in this study by using the Global Ionosphere and Thermosphere Model (GITM). It is found that although Joule heating can be significantly enhanced by the small-scale electric field variabilities, the corresponding change in the particle precipitation tends to depress such enhancement, which is not negligible on the dusk side. [Preview Abstract] |
Saturday, October 26, 2019 11:42AM - 11:54AM |
H01.00009: Study of Magnetopause Motion based on multiple Crossing of THEMIS Spacecraft Fatemeh Bagheri, Ramon E Lopez, Pauline Dredger, Richard Bonde, Cristina Xing, Chelsi Nelson, Nabin Chapagain, Michelle Bui The magnetopause is a thin current-carrying plasma surface layer which is the magnetic discontinuity separating the weaker interplanetary magnetic field from the stronger Earth magnetic field. The location of the magnetopause is determined by the balance between the pressure of the dynamic planetary magnetic field and the dynamic pressure of the solar wind. As the solar wind pressure increases or decreases, the magnetopause moves inward or outward in response. In this work, we study the magnetopause motion and structure based on observation from multiple crossings of the magnetopause of THEMIS spacecraft with simultaneous solar wind observations. The solar wind data shows the IMF was radial and the velocity of solar wind was almost constant.~ The thickness of the current layer is about one gyro diameter. The average magnetopause speeds were in the low 10's of km/s, however, speeds up to 100km/s were observed. During this period there is no evidence of hot flow anomalies in the magnetosheath near the magnetopause. Although the orientation of the IMF during the observations would have been predicted to cause wavy motions of the magnetopause boundary, in our study there is no evidence of such kind of motion.~~ [Preview Abstract] |
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