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 T03: Astrophysics and Space Science II |
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Chair: Walter Thompson, UHCL Room: STEM 2115 |
Saturday, October 23, 2021 10:00AM - 10:36AM |
T03.00001: Resonant Mode Coupling in Red Giants Invited Speaker: Nevin Weinberg Asteroseismic studies of red giants generally assume that the oscillation modes can be treated as linear perturbations to the background star. However, Kepler observations show that the oscillation amplitudes increase dramatically as stars ascend the red giant branch. Thus, the linear approximation may not always be valid. In previous work, we showed that mixed modes in red giants are unstable to nonlinear three-wave interactions over a broad range of stellar mass and evolutionary state. Here we solve the amplitude equations that describe the nonlinear mode dynamics for large networks of resonantly coupled modes. We find that nonlinear interactions can lower the energy of gravity-dominated mixed modes by $>80\%$ compared to linear theory predictions. However, they have only a mild influence on the energy of pressure-dominated mixed modes. We conclude that resonant mode coupling can have a potentially detectable effect on the oscillations of highly evolved red giants, though it cannot account for the population of moderately evolved red giants that exhibit dipole modes with unusually small amplitudes. [Preview Abstract] |
Saturday, October 23, 2021 10:36AM - 10:48AM |
T03.00002: TTU directed searches for continuous gravitational waves Benjamin Owen I summarize the Texas Tech group's recent searches of publicly available Advanced LIGO data for continuous gravitational waves. Detections of gravitational waves from mergers of binary black holes and/or neutron stars have become common. Continuous wave signals from single neutron stars have not yet been detected, so they are the new frontier. Continuous gravitational waves couple to the crystal layers of the star and possibly the viscosity and thermal properties of the fluid core, unlike the bulk properties revealed in binary mergers; so they can open up a new window into neutron star interiors. [Preview Abstract] |
Saturday, October 23, 2021 10:48AM - 11:00AM |
T03.00003: Calculation of Large-Scale Structure Power Spectra in a Spherical Fourier Bessel Basis Brandon Khek, Henry Gebhardt, Olivier Dore Upcoming deep (high redshift) wide-angle (large survey area) galaxy redshift surveys such as the High-Latitude Spectroscopic Survey of the Nancy Grace Roman Space Telescope and SPHEREx are estimated to measure the redshifts of millions of galaxies. A spherical Fourier Bessel (SFB) basis for the power spectrum will fully maximize the extraction of cosmological information from this data, and using this basis, we exploit the statistical efficiency of calculations in the Fourier space by naturally separating the angular and radial components over a sphere. In this project, we provide code written in Julia to calculate the SFB power spectrum which is customizable for the parameters set by the survey data and assumed cosmology. By providing robust calculations of the SFB power spectrum, our code plays a crucial role in the analysis of wide-angle galaxy surveys and ensures unbiased results on large scales. The code will eventually be leveraged to study how physical effects, such as baryon acoustic oscillations, redshift-space distortions, primordial non-Gaussianity, and modified theories of gravity, manifest themselves in the SFB power spectrum. [Preview Abstract] |
Saturday, October 23, 2021 11:00AM - 11:12AM |
T03.00004: Density Anomalies in the Subsurface of Mars Determined from the Gravity Field Juan Hinojosa The high degree and order (n,m \textgreater 20) Bouguer gravity field of Mars was used to calculate the subsurface density anomalies in eleven study areas associated with past volcanic activity. The sources of the gravity field were modeled with a Pratt layer of uniform thickness. A series of density anomalies consistent with the gravity field in each area was generated by varying the thickness and depth of the Pratt layer. The densities associated with the gravity lows in each area were then analyzed to determine the combinations of model parameters that would yield densities equal to the density of basalt magma (2700 \textit{kg m}$^{-3})$. The depth to sources was constrained by observing the rate of decay of the near-surface, short-wavelength Bouguer gravity power spectrum. Using the depth to sources, a maximum Pratt layer thickness coinciding with the 2700-\textit{kg m}$^{-3}$ density curve was obtained. The results indicate that subsurface densities corresponding to basalt magma are consistent with the observed Bouguer gravity field in all of the study areas for values of Pratt layer thickness of \textasciitilde 7--16 \textit{km}. Furthermore, the results appear to suggest that Mars may still contain isolated pockets of basalt magma in its subsurface. [Preview Abstract] |
Saturday, October 23, 2021 11:12AM - 11:24AM |
T03.00005: The Host Galaxies of Hybrid Morphology Radio Sources Victoria Catlett, Andra Stroe The relativistic jets from powerful radio galaxies take on one of two morphological classifications, called Fanaroff-Riley I (FR-I) and II (FR-II), based on the location of their termination hot spot. Hybrid morphology radio sources (HyMoRS) contain one of each type of jet, presenting a unique opportunity to study the conditions which give rise to the dichotomy. We conduct the first investigation into whether the host galaxy properties can influence jet formation. Through optical spectroscopy and ultraviolet-optical-infrared photometry, we analyze the emission characteristics, and we evaluate the broad characteristics of five HyMoRS host galaxies at intermediate redshifts (0.4 \textless z\textless 1.5). We discuss how the results allow us to differentiate between formation theories. [Preview Abstract] |
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