Bulletin of the American Physical Society
Four Corners Section 2022 Meeting
Volume 67, Number 14
Friday–Saturday, October 14–15, 2022; Albuquerque, New Mexico
Session B04: Astrophysics I |
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Chair: Denise Stephens, Brigham Young University Room: UNM PAIS 1160 |
Friday, October 14, 2022 10:00AM - 10:24AM |
B04.00001: Characterizing magnetic activity through the lens of sub-subgiant stars Invited Speaker: Natalie Gosnell As our knowledge of stellar evolution unfolds the complexities introduced by magnetic stellar activity become more apparent. One example is seen in sub-subgiants, magnetically active stars with starspots that sit below the subgiant branch and red of the main sequence on a cluster color-magnitude diagram. Sub-subgiants exhibit strong variable light curves as starspots rotate in and out of view. There is much to learn from one such system: S1063, a prototypical sub-subgiant in M67 with a rotation period of 23.5 days. A two-temperature spectral decomposition technique allows us to constrain the surface conditions of S1063, including the spot covering fraction and spot and ambient photosphere temperatures. We link these surface condition constraints to a multi-year light curve, finding the spot covering fraction varies between 20% to 45% over four years. This analysis brings to light some important nuances when considering observational and theoretical comparisons of spotted stars. We are currently expanding this study by observing field sub-subgiants using IGRINS with contemporaneous or near-contemporaneous TESS coverage. This technique opens the possibility of characterizing the surface conditions of many more spotted stars than previous methods, allowing for larger studies capable of testing theoretical models of magnetically active stars. |
Friday, October 14, 2022 10:24AM - 10:36AM |
B04.00002: Avoiding the Mass Injection problem for Astrophysical Jets by using Directed Gravity (Relativistic Beaming of the Gravitational Force.) Bradford C Blake Astrophysical jets emitted at the poles of many black holes are difficult to explain because the gravitational force is presumed too powerful to allow the escape of massive particles from the hole. However, if Directed Gravity (relativistic beaming of the gravitational force) applies to black holes, then the gravitational force in the polar directions should be reduced, allowing the pressure differential to overcome gravity, such that jets of superfluid neutrons can escape the black hole at the poles. |
Friday, October 14, 2022 10:36AM - 10:48AM |
B04.00003: Radio Searches of Fermi Unassociated Gamma-Ray Sources Seth M Bruzewski, Frank K Schinzel, Greg B Taylor The recent release of the 12-year Fermi-LAT point source catalog (4FGL-DR3) includes a variety of new unassociated gamma-ray sources, adding to the already extensive list of high-energy astrophysical objects which have no known counterpart in any other wavelength regime. Here we present our ongoing efforts toward providing associations and identifications for sources in this upcoming catalog. This includes blind searches using multiple radio catalogs, as well as targeted searches in particular fields of interest. We also highlight early results from deep integration observations of selected fields with the aim of uncovering faint pulsar and high-z quasar association candidates. |
Friday, October 14, 2022 10:48AM - 11:00AM |
B04.00004: Detecting and Analyzing Meteor Persistent Trains in Widefield Optical Images Logan Cordonnier, Greg B Taylor, Kenneth S Obenberger Persistent trains (PTs) are lingering, self-emitting optical emissions sometimes observed after the initial meteor streaks. Based on data from the Leonids outbursts in 1999 – early 2000, these phenomena have been associated with bright, high velocity meteors, located in the brightest portion of the meteor. To further examine this population of PT-producing meteors, a widefield camera was deployed at the Sevilleta National Wildlife Refuge in New Mexico to take long exposure (5 second) images. These images were then run through a custom pipeline to identify PTs, with 40 being identified thus far. Using the Global Meteor Network, a database of observed meteor events and their parameters, the statistics of these PTs were determined. It was found that the majority of observed PTs occurred at relatively slow speeds, and that dim meteors (minimum peak magnitude: 1.22) were also capable of producing PTs. Additionally, in a few cases the PT occurred in the dim portion of the meteor streak. Cursory analysis shows that PT production is dependent on the mass rather than the energy of the meteor. These observations seem to challenge the previous assumptions about the nature of PTs.
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Friday, October 14, 2022 11:00AM - 11:12AM |
B04.00005: Almost a decade of pulsar observations below 100 MHz Pratik Kumar, Greg B Taylor, Kevin Stovall, Jayce Dowell, Stephen M White Recent advancements in low-frequency radio observations of pulsars are providing new insights into the properties as well as the effect of the interstellar medium. Pulsars are strongly polarized radio sources that probe the density and magnetic field variations along the line of sight to the Earth. For example, one can monitor the effect of the interstellar medium on the pulsar Dispersion Measure (DM) which has an inverse square dependence on the observing frequency, making low-frequency observations preferable for such measurements. The Long Wavelength Array (LWA) has an active pulsar monitoring program, where we regularly observe a set of ~100 pulsars below 100 MHz, studying these effects in time and frequency. Here we present a systematic study of these objects over almost a decade of observations, and what we have learned about the local interstellar medium. |
Friday, October 14, 2022 11:12AM - 11:24AM |
B04.00006: Modeling Solids in Nuclear Astrophysics with Smoothed Particle Hydrodynamics Irina Sagert, Oleg Korobkin, Bing-Jyun Tsao, Hyun Lim, Ingo Tews, Michael Falato, Julien Loiseau Smoothed Particle Hydrodynamics (SPH) is a frequently applied tool in computational astrophysics. In addition to solving the fluid dynamics equations, some problems, for example when involving asteroids and asteroid impacts require the inclusion of material strength to accurately describe the dynamics of the system. In nuclear astrophysics, neutron stars and their binary mergers are usually approached as purely fluid dynamics problems. However, neutron stars also a have solid component, the crust. The latter is the strongest material known in nature but is usually not considered when modeling the dynamical of neutron stars in 3D. Here, we present the first 3D simulations of neutron-star crustal toroidal oscillations with SPH including material strength. We use the Los Alamos National Laboratory SPH code FleCSPH which has been developed as a general-purpose fluid dynamics code with material strength and has been applied to compact star oscillations and mergers. In the first half of the talk, we describe the implementation of solid material modeling in FleCSPH and present standard tests including the Verney implosion and the Taylor anvil impact. The second half is dedicated to simulations of crustal oscillations in the fundamental toroidal mode where we focus on exploring approaches to suppress numerical noise which can otherwise disturb the shear motion. |
Friday, October 14, 2022 11:24AM - 11:36AM |
B04.00007: Studies of Mass Loss in Pulsating Asymptotic Giant Branch Stars Henry A Prager, Lee Anne M Willson, Joyce A Guzik, Michelle J Creech-Eakman, Massimo Marengo, Qian Wang Asymptotic Giant Branch stars are the final actively fusing stage of stellar evolution. These stars undergo mass loss, ejecting their envelopes through a pulsation and dust-driven wind. This recycles material back into the interstellar medium as well as adding in new materials such as nitrogen, heavy metals, and cosmic dust. |
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