Date of Award
2024
Document Type
Open Access Dissertation
Degree Name
Doctor of Philosophy in Physics (PhD)
Administrative Home Department
Department of Physics
Advisor 1
Petra Huentemeyer
Committee Member 1
Brian E. Fick
Committee Member 2
David F. Nitz
Committee Member 3
Fan Dai
Abstract
HESS J1809-193 is an unidentified TeV source discovered in 2007 by the High Energy Stereoscopic System(H.E.S.S.) Collaboration. The emission originates in a region that is rich in cosmic-ray accelerators, including several supernova remnants and pulsars, including SNR G11.1+0.1, SNR G11.0-0.0, and the young radio pulsar PSR J1809-1917. Originally classified as a pulsar wind nebula candidate, recent studies show the peak of the TeV region overlapping with a system of molecular clouds and revising the original classification for other scenarios, including a pure hadronic scenario. This dissertation presents the morphological and spectral study of HESS J1809-193 using 2139 days of data from the High-Altitude Water Cherenkov(HAWC) observatory. This analysis identifies a single extended source in the region: HAWC J1809-192. The morphology of HAWC J1809-192 is described with a Symmetric Gaussian model with a 1$\sigma$ radius of 0.21$^\circ$. The spectral energy distribution of the source is fit by a power law with a flux normalization of $3.53\pm0.31 \times 10^{-14}$ at 10 TeV and a spectral index of $2.42\pm0.05$. It shows no clear cutoff at high energies and emitting photons up to 210 TeV energy. Hence, to explain the origin of these photons, we model the multi-wavelength observations for the HAWC J1809-192 region using lepto-hadronic and time-dependent leptonic models. In the lepto-hadronic scenario, a proton spectrum fits the data for HAWC J1809-192, assuming the observed TeV $\gamma$-rays are produced by $\pi^0$-decay. The fit results show that the proton energy budget required to produce the $\gamma$-rays is well below the energy released during the supernova explosion($\sim 10^{51}$erg). In the time-dependent leptonic scenario, an electron spectrum fits the data for HAWC J1809-192, assuming the observed TeV $\gamma$-ray emission is produced by the Inverse Compton process. The fit results show that about 67$\%$ of the pulsar spin-down luminosity is converted to electrons and is within the energy budget of the PSR J1809-1917. The "relic" electrons injected over the source's lifetime can reproduce the HAWC spectrum. Both models support the two different interpretations of the emission of HAWC J1809-192, and more data is required to provide conclusive evidence.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License
Recommended Citation
Babu, Rishi, "Study of Particle Accelerators in the Universe with the HAWC Observatory", Open Access Dissertation, Michigan Technological University, 2024.
