Physical Processes Commons^™

Cosmic Duets: A Search For Binary Supermassive Black Holes In Merging Galaxies, Sagar Adhikari

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Galaxies are vast cosmic islands of stars, dust, and gas. They come in various shapes and sizes. They might look static for the timescales we are used to, but they are dynamic and collisional systems that can merge with other galaxies to make bigger galaxies. Most galaxies, including the Milky Way, host a central supermassive black hole (SMBH) with a mass greater than a million (sometimes a billion) times the mass of the Sun. When galaxies merge, their SMBHs form a binary system before ultimately merging. These cosmic duets are of great interest to astronomers and astrophysicists as they are …

Chemical & Electromagnetic Signatures Of Binary Neutron Star Mergers, Benjamin Amend

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Binary neutron star (BNS) mergers are some of the most energetic events in the universe, producing both short gamma-ray bursts (GRBs) and kilonovae. GRBs are brief, bright flashes of gamma rays, powered by ultra-relativistic jets launched during the merger. These jets produce a prompt burst of gamma rays, followed by a broadband afterglow generated by external shocks as the outflow interacts with the surrounding medium. Kilonovae are optical-infrared transients from the radioactive decay of heavy, neutron-rich nuclei formed through the rapid neutron capture process (r-process) in the merger ejecta. Together, GRBs and kilonovae provide unique laboratories for probing fundamental physics …

To The Torus And Beyond: An X-Ray Study Of Agn Tori Morphology, Andrealuna Pizzetti

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Active Galactic Nuclei (AGN) are among the Universe's most energetic and powerful objects, fueled by an accreting supermassive black hole (SMBH) at the host galaxy's center, surrounded by a toroidal structure of dusty gas. Ultraviolet photons arising from the accretion disk get up-scattered to X-rays via inverse Compton scattering by hot electrons close to the accretion disk. Being produced in the very center of the AGN, X-ray photons are powerful messengers that probe the physics of the accretion system and the matter in the surroundings. The torus, formerly considered homogeneous, appears to be a more complex structure of clouds with …

An Investigation Of The Accretion Processes In T Tauri And Herbig Ae/Be Systems Using High Resolution Optical And Near-Infrared Spectroscopy, Joshua Kern

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Star and planet formation is intimately tied to the accretion of material from the environments in which they form. During the formation process, disks of gas and dust develop in young stellar objects through which material is facilitated to the star and forming planets. Theoretical models of these accretion processes invoke viscous spreading via hydrodynamics, as well as more complex interactions with magnetic fields be it from the stellar component or the formation environment in order to catalyze these mass flows. These accretion models predict various scenarios including magnetospheric accretion as well as supersonic accretion flows in the disk atmosphere …

Spectroscopy Of Highly Charged Ions For Astrophysical And Laboratory Plasma Diagnostics, Yang Yang

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Electron beam ion traps (EBITs) are small-scale laboratory devices that create and trap highly charged ions (HCI) for spectroscopic studies. These devices create plasma conditions resembling astrophysical environments like stellar winds and supernova remnants, providing valuable insights into astrophysical plasma. Theoretical models for such systems require incorporating relativistic and quantum electrodynamics effects, making experimental studies of HCIs essential for benchmarking these theories.

Spectral analysis of astrophysical and laboratory plasma requires understanding the ionization balance. Accurate atomic data, including excitation, ionization, and recombination cross sections, along with precise knowledge of operating conditions such as electron beam density, electron beam energy, and …

Simulating The Eccentricity Evolution Of Accreting Equal-Mass Binaries: Numerical Sensitivity To The Computational Domain Size And Grid Resolution, Zhongtian Hu

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With high resolution hydrodynamics simulations, we show that the optimal values of domain radius and grid resolution for the software Sailfish when simulating time-based eccentricity evolution of equal mass, non-circular accreting binaries in a circumbinary disk to be $r_{\rm out} \leq 15a$ and $\delta x / a \le 0.01 $. These values provide a useful guideline for optimizing the performance of simulation runs while maintaining scientific accuracy. Each artificial parameter is probed with 15 runs of 2000 orbits each.

Cosmic Diffuse Neutrino And Gamma-Ray Backgrounds In The Mev Regime, Ilukpitiye Samalka Anandagoda

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Cosmic Multi-Messenger backgrounds include relic diffuse components created in the early Universe and contributions from individual sources. In this dissertation, I present the work done in Anandagoda (2019); Anandagoda et al. (2020, 2023) where type Ia (SNe Ia) and core-collapse supernovae (CCSNe) contributions to the diffuse neutrino and gamma-ray backgrounds in the MeV regime are studied. These backgrounds are referred to as DSNB and DSGB respectively. Based on this work, the diffuse SN Ia background is ~10⁶ times lower (for electron antineutrinos) than the CCSN background making it negligible. The predicted DSNB electron antineutrino flux at earth in the …

The Pursuit For Gamma-Ray Emitting Pulsar Wind Nebulae With The Fermi-Large Area Telescope, Jordan Eagle

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Pulsar wind nebulae are highly magnetized particle winds, descending from core collapse supernovae (CC SNe), and each powered by an energetic, rapidly rotating neutron star. There are at least 125 Galactic pulsar wind nebulae (PWNe) that have been discovered from radio wavelengths to TeV gamma-rays, the majority of which were first identified in radio or X-ray surveys. An increasing number of PWNe are being identified in the TeV band by ground-based air Cherenkov Telescopes such as HESS, MAGIC, and VERITAS such that they constitute the dominant source class of Galactic TeV emitters. High-energy sources like PWNe may be responsible for …

Exploring The Glow Of The Universe In Gamma-Rays And Hunting Distant Agn, Changam Meenakshi Rajagopal

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The entirety of the γ-ray radiation permeating our Universe is encoded in the extragalactic γ-ray background. This is a superposition of resolved sources, mostly powerful relativistic jets powered by supermassive black holes, i.e., blazars, and an unresolved isotropic component, aka, the diffuse isotropic gamma-ray background (IGRB). Studying the IGRB can help unveil its composition, as well as unearth multi-messenger relationships between the intensities of PeV neutrinos, ultra high energy cosmic rays (> 1018 eV), and sub-TeV γ-rays. The comparable energy budgets of these three phenomena (neutrinos, UHECR, and γ-rays) indicates a physical connection or a common source amongst them. On …