Discovery Of Localized Tev Gamma Ray Sources And Diffuse Tev Gamma Ray Emission From The Galactic Plane With Milagro Using A New Background Rejection Technique PDF Download

As neutrally-charged astrophysical messengers, gamma rays serve as powerful tools for determining the origins of incredibly high-energy particles from across our universe [1]. Gamma rays are considered to have the highest energy of all electromagnetic radiation, with energies spanning from 0.5 MeV to about 100 TeV [2]. Although lower-energy gamma rays can originate from within our solar system, gamma rays in the GeV and TeV ranges tend to originate from sources beyond our solar system [1]. By investigating these sources, we can understand more about the astrophysical phenomena that characterize the most extreme conditions in our universe, such as supernova remnants, gamma-ray bursts, and pulsars [3]. The High Altitude Water Cherenkov Gamma-Ray Observatory (HAWC) is one of the most sensitive gamma-ray detectors in the very high energy (VHE) regime, with the capability to observe gamma rays from 100 GeV and 100 TeV [4]. In 2017, HAWC conducted a blind search encompassing two thirds of the sky and 508 days of observations [4]. In this search, there were 16 VHE gamma-ray excesses that were unassociated with any previously discovered gamma-ray sources [4]. Now with data from 1523 days of observations, we begin to study these 16 unassociated candidate TeV sources in more detail. In this work, we update the locations of maximum significance for these candidate TeV sources and analyze the temporal progression of their significance and flux. This allows us to determine if they have faded into the diffuse gamma radiation or if they can still be considered unassociated candidate TeV sources. We then reevaluate the morphologies and spectral energy distributions of the remaining sources and discuss any recent observations from other gamma-ray observatories. We find that 10 of these 16 unassociated candidate TeV sources can still be considered candidate sources. In the future, we plan to use data from other observatories to continue to put better constrains on the morphology and spectral energy distributions for these sources and better understand their acceleration mechanisms. In addition, we plan to conduct a similar investigation with new HAWC excesses discovered with recent data from 1523 days of observations [5]. By investigating these excesses in the high-energy gamma-ray sky, we can discover and characterize new extreme astrophysical phenomena and ultimately uncover valuable information about the physical mechanisms that accelerate particles to very high energies.