Bulletin of the American Physical Society
2021 Virtual Conference for Undergraduate Women in Physics
Friday–Sunday, January 22–24, 2021; Virtual
Session U14: Astrophysics and Cosmology VIIIInteractive Live
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Chair: Alexia McKenzie, University of California, Santa Cruz |
Sunday, January 24, 2021 12:00PM - 12:10PM |
U14.00001: White Dwarf Stars Observed with NASA's Kepler & K2 Space Telescope Kendall Shepherd, Weston Hall, Barbara Castanheira Endl. PhD Ninety-five percent of all single stars will evolve into white dwarf stars. On a white dwarf’s cooling sequence of the HR diagram, they pass through three distinct instability strips. At these temperatures, white dwarfs are observed to pulsate due to hydrogen recombination. Variable stars allow researchers to study stellar interiors. Variable and non-variable white dwarf stars were searched for in short cadence observations and by cross-matching data with Gaia and SDSS. Using data from campaigns 0 - 19 of NASA's Kepler/K2 space telescope, hundreds of white dwarf stars were identified. A color magnitude diagram was created of the white dwarf cooling sequence from the stars with a color index less than 0.7. These stars were analyzed for variability, and stricter bounds were implemented on the instability strips of the cooling sequence. This work will enable better models of the variability of these stars, and help to determine driving factors of stellar pulsation. [Preview Abstract] |
Sunday, January 24, 2021 12:10PM - 12:20PM |
U14.00002: Thunderstorm Identification for LIGO Lee Capistran, Brina Martinez, Guillermo Valdes h $-abstract-$\backslash $pardScattered laser light, undesirably reflected from vibrating surfaces, generate noise that affects the sensitivity of the Laser Interferometer Gravitational-Wave Observatory (LIGO). These surfaces, such as the walls of the vacuum chambers enclosing the detectors, can be vibrating due to locally created seismic activity such as thunderstorms, trains, or other anthropogenic activities. In this work, we used a previously written script to extract features of noise believed to originate from thunderclaps and run them through machine learning techniques to identify acoustic noises. We used K-Nearest Neighbors to train the data that is later implemented in determining whether the acoustic signals being picked up are that of a thunderstorm or not. Determining the source of disturbances is important in the constant development and maintenance of LIGO's infrastructure and data quality control.$\backslash $pard-/abstract-$\backslash $\tex [Preview Abstract] |
Sunday, January 24, 2021 12:20PM - 12:30PM |
U14.00003: Effects of Galactic Tide on Trans-Neptunian Objects Jingyu Zhang Sheppard and Trujillo first predicted a planet to exist far beyond Pluto in 2014, a hypothetical planet called Planet Nine. Planet Nine can shepherd extreme trans-Neptunian objects (TNOs) into clustering orbits. Previous study indicates that TNOs with semimajor axis greater than 250 AU show clustering in orbital orientation and planes. In this project we examined the dynamical effects of galactic tidal force on the outer solar system and the hypothesis of Planet Nine. We considered the following ingredients that can affect the orbits of the TNOs --- the Neptune, the gravitational potential J2 term (the inner giant planets), Planet Nine and the galactic tidal force. We used the N-body simulation method in \textit{Mercury} package to calculate the integration and plot the four orbital elements versus time. The result shows us that both galactic tidal force and the Planet Nine can lead to clustering on orbital orientation, though with different properties. Different behaviors of clustering due to galactic tidal force and Planet Nine can help the scientists constrain the properties of Planet Nine. For studying the outer solar system and exoplanets, it is imperative to understand the dynamic property of Planet Nine and the effect of galactic tidal force. [Preview Abstract] |
Sunday, January 24, 2021 12:30PM - 12:40PM |
U14.00004: Visual Identification of Jellyfish Galaxies in Galaxy Clusters Using Deep, High-Resolution Optical Images Natalie Rugg, Shenming Fu, Ian Dell'Antonio Jellyfish galaxies, spiral galaxies undergoing ram-pressure stripping while entering the intracluster medium, reveal the dynamics and timescale of a gas-rich spiral transforming into a gas-poor elliptical galaxy. To identify smaller, higher-redshift jellyfish galaxies, I composited a deep, high-resolution image of galaxy cluster Abell 1650 from raw Dark Energy Camera visits, a process that my lab group has since repeated for 17 other clusters. After first removing bias and flat file signatures and cosmic rays, I calibrated the images to existing reference catalogues (GAIA, SDSS, and Pan-STARRS) and warped the images to form a skymap. I repeated this process for each filter band and coadded the resulting images together to create one multi-band image. Originally for dark matter microlensing of galaxy clusters, I have used these images to search for jellyfish galaxies, which are characterized by a unilateral trail of stripped, star-forming gas. I have identified over 25 candidates in 9 galaxy clusters using established visual criteria. Future work will entail calculating 3D velocities and determining the significance of jellyfish galaxies to the evolution of galaxies. [Preview Abstract] |
Sunday, January 24, 2021 12:40PM - 12:50PM |
U14.00005: Characterizing the Atmospheres of Low-Gravity M-dwarfs Isabela Huckabee, Aishwarya Iyer, Michael Line The objective of this study is to model the atmospheres of low surface gravity M-dwarfs.~Ultimately this will aid in investigating observed trends in the physical properties of these stars unexplained by models thus far. A growing collection of low surface gravity M-dwarfs (Faherty et al.,2016; Patience et al., 2012) have appeared brighter in the infrared than typical M-dwarfs and they hypothesize this may be from a thick or high-altitude cloud layer, or dust absorption. Our code simulates a 1-D M-dwarf stellar atmosphere and determines the effective temperature, surface gravity, and atmospheric bulk chemical properties such as metallicity and carbon-to-oxygen ratios. We incorporate radiative transfer, equations of state, and convection to determine the model star's spectra, thermal structure, and molecular/elemental mixing ratios. We plan to fit low-resolution spectral data for cloudy, low gravity M-dwarfs and address color and brightness trends seen with these special class of stellar objects. The results will help gain a more in-depth understanding of the physical processes in low surface gravity M-dwarfs and therefore better understanding of potentially habitable exoplanets orbiting them. [Preview Abstract] |
Sunday, January 24, 2021 12:50PM - 1:00PM |
U14.00006: X-ray Evidence of a Stellar Wind Mass-Loss Rate Increase in the O Supergiant $\zeta$ Puppis over 18 Years Jiaming Wang During 2018 and 2019, NASA's \textit{Chandra X-ray Observaotry} carried out a set of observations on $\zeta$ Pup, a hot and luminous star that is classified as an O supergiant. The observations supplement data acquired in 2000 and motivate analysis on the long-term variations in $\zeta$ Pup's stellar wind properties. In stars like $\zeta$ Pup, hot X-ray emitting plasma is distributed throughout a colder X-ray absorbing stellar wind. Emission lines from the hot plasma are Doppler-broadened due to the high wind speeds and are made asymmetric by absorption. Fitting 10 strong X-ray emission lines with a line profile model that incorporates those wind properties, we find a stellar mass-loss rate of $2.47 \pm 0.09 \times 10^{-6} \ensuremath{{\mathrm {M_{\sun}~{\mathrm yr^{-1}}}}}$, which represents a 40 percent increase since 2000. This surprising result is also accompanied by a 13 percent increase in X-ray emission flux. Because the result is unexpected, we supplement the model fitting with a non-parametric analysis and also with Gaussian fitting to confirm the changes in the emission line profile properties. [Preview Abstract] |
Sunday, January 24, 2021 1:00PM - 1:10PM |
U14.00007: Modeling N$_{\mathrm{2}}$H$^{\mathrm{+}}$ Emission around DM Tau Amina Diop Turbulence is one of the key processes influencing planet formation, hence we are investigating the mechanism driving it by studying its vertical structure. We have been working with the disk around DM Tau since it is so far the only system where significant non-zero turbulence has been robustly detected in its upper layers using molecular line emission. To estimate turbulence near the midplane in the outer disk, we are using N$_{\mathrm{2}}$H$^{\mathrm{+}}$(3-2) and DCO$^{\mathrm{+}}$(4-3) emissions alongside a ray-tracing radiative transfer code with a parametric model of the disk structure and Markov Chain Monte Carlo methods. Our current models for N$_{\mathrm{2}}$H$^{\mathrm{+}}$ display the same features as the actual emission but they fail to capture the outer emission. This discrepancy could potentially be accounted for by revisiting the CO freeze-out temperature. Our results also reveal that the CO snowline is closer to the star than previously determined. Finally, the DCO$^{\mathrm{+}}$(4-3) emission is depleted between 104 and 156 au; which could be linked to a combination of CO freeze-out, non-thermal desorption, and radial migration of dust grains. [Preview Abstract] |
Sunday, January 24, 2021 1:10PM - 1:20PM |
U14.00008: Fermi-LAT gamma-ray observations of 4FGL J0658. 6$+$ 0636, candidate counterpart to the neutrino event IC201114A Isabella Guilherme, Reshmi Mukherjee, Qi Feng Establishing a gamma-ray source also as a neutrino emitter could shed light upon the processes that produce ultra-high-energy cosmic rays. The neutrino event IC201114A was detected by IceCube on 2020-11-14 in the vicinity of~the catalogued gamma-ray source 4FGL J0658.6$+$0636, associated with the active galaxy NVSS J065844$+$063711. We report an analysis of gamma-ray observations of 4FGL J0658.6$+$0636 over the timescales of 1-day, 1-month, 6-months, 1-year, 5-years and 10-years prior to the event with the Large Area Telescope (LAT) onboard NASA's Fermi Gamma-ray Space Telescope. This was done to better understanding the gamma-ray variability of the source and to search for any temporal correlation between the IceCube event and the gamma-ray emission. We found neither evidence for strong gamma-ray~variability nor a significant detection with the time windows up to 1 year prior to the IceCube event. The lack of temporal correlation between gamma rays from 4FGL J0658.6$+$0636 and the neutrino event suggests that either the neutrino event is not from this source or the gamma rays are absorbed in the emitting region. Regular monitoring of this source and timely followup observations of future IceCube events will continue [Preview Abstract] |
Sunday, January 24, 2021 1:20PM - 1:30PM |
U14.00009: Exploring properties of higher-order modes in gravitational wave emission from binary black hole merger events Jennifer Sanchez, Alan J. Weinstein, Colm Talbot h $-abstract-$\backslash $pardAdvanced LIGO and Advanced Virgo have confidently detected a number of gravitational wave signals, including waves from dozens of binary black hole mergers and two mergers of binary neutron stars. Each observation contains encoded information about the physical properties of the binary system. As gravitational-wave detectors continue to improve their sensitivity and thus their astronomical reach, the improvements will allow us to detect rarer systems and make more confident statements regarding their source properties. In order to fully characterize the gravitational wave observations, we rely on numerical and analytical models that approximate the signal waveforms from the emitted source as specified by the source parameters (e.g. masses, spins, sky location, etc). The dominant emission frequency of gravitational waves from compact binary coalescence is at twice the orbital frequency; however, recently published events (e.g. GW190412) have demonstrated evidence of subdominant, higher-order harmonic contributions. In this talk, I will discuss a study exploring the impact of including (using newly improved signal models) or neglecting these higher-order modes in gravitational wave signals on the signals' sources' inferred physical properties.$\backslash $pard-/abstract-$\backslash $\tex [Preview Abstract] |
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