Bulletin of the American Physical Society
APS April Meeting 2023
Volume 68, Number 6
Minneapolis, Minnesota (Apr 15-18)
Virtual (Apr 24-26); Time Zone: Central Time
Session M13: Gamma Ray Astronomy I |
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Sponsoring Units: DAP Chair: Tiffany Lewis, NASA Goddard Space Flight Center Room: Marquette IV - 2nd Floor |
Monday, April 17, 2023 10:45AM - 10:57AM |
M13.00001: Hadronic versus leptonic origin of gamma-ray emission from supernova remnants Nicholas J Corso, Damiano Caprioli, Rebecca Diesing GeV and TeV emission from the forward shocks of supernova remnants (SNRs) indicates that they are capable particle accelerators, making them promising sources of Galactic cosmic rays (CRs). However, it remains uncertain whether this γ-ray emission arises primarily from the decay of neutral pions produced by very high energy hadrons, or from inverse-Compton and/or bremsstrahlung emission from relativistic leptons. By applying a semi-analytic approach to non-linear diffusive shock acceleration (NLDSA) and calculating the particle and photon spectra produced in different astrophysical environments, we parametrize the relative strength of hadronic and leptonic emission. We show that, even if CR acceleration is likely to occur in all SNRs, the observed photon spectra may instead primarily reflect the environment surrounding the SNR, specifically the ambient density and radiation field. We find that the most hadronic-appearing spectra are young and found in environments of high density but low radiation energy density. This study aims to guide the interpretation of current γ-ray observations and single out the best targets of future campaigns. |
Monday, April 17, 2023 10:57AM - 11:09AM |
M13.00002: Polarization of Inverse Compton Scattering without Ultrarelativistic Approximation Anderson Chun Ming Lai, Kenny Chun Yu Ng Inverse Compton (IC) scattering is an essential radiative process in many high-energy astrophysical setups. Typical calculations on the differential cross-section adopted isotropic or ultrarelativistic approximations. We develop a new formalism to compute IC scattering without the above assumptions and with improved numerical stability compared to previous results. Our calculations can be employed in extensive astrophysical scenarios. An application is for computing the differential polarization of photons after anisotropic IC scattering, which is seldom explored with numerical approaches and is often inconsistent in previous contexts. This work is timely for current and future high-energy missions with polarimetry capability. |
Monday, April 17, 2023 11:09AM - 11:21AM |
M13.00003: Studies of the Gamma-ray Binary LS 5039 with HAWC Observatory Dezhi Huang LS 5039 is a gamma-ray binary with an orbital periodicity of 3.9 days located about 1.5 degrees from the galactic plane. Previously, the H.E.S.S. telescope detected very high energy gamma-ray emissions from this source and measured the spectral energy in a broad inferior conjunction phase (0.45100 TeV and discuss possible gamma-ray production mechanisms. |
Monday, April 17, 2023 11:21AM - 11:33AM |
M13.00004: Physical properties of the brightest gamma-ray burst based on observations by the Fermi Gamma-ray Burst Monitor Peter Veres GRB 221009A was the brightest gamma-ray burst (GRB) detected since the start of GRB observations. Even though it saturated Fermi-GBM, it presents a rich and unique data set to test theoretical models of gamma-ray production. We present spectral analysis of the pulses not affected by instrumental saturation and confront the synchrotron emission model with the observations. Interestingly, the afterglow is also detected by GBM. We determine the transition from prompt emission to afterglow, and derive the Lorentz factor of the outflow using multiple methods. |
Monday, April 17, 2023 11:33AM - 11:45AM |
M13.00005: Analysis of LHAASO J2108+5157 with HAWC Observatory data Michael Martin PeVatrons are able to accelerate cosmic rays up to PeV energies, which can result in gamma rays with energies greater than 100 TeV. LHAASO J2108+5157 is a PeVatron candidate seen significantly by Large High Altitude Air Shower Observatory (LHAASO) above 100 TeV. The region has been reported on by both LHAASO and the first Large-Sized Telescope (LST-1), but its origins remain unknown. This source is seen significantly above 6 TeV by the High Altitude Water Cherenkov (HAWC) Observatory in the newest dataset. There is an ongoing joint analysis with Very Energetic Radiation Imaging Telescope Array System (VERITAS) and HAWC data. I will present the results of the analysis with HAWC data in the region, as well as the multi-wavelength modeling including both HAWC and VERITAS data. |
Monday, April 17, 2023 11:45AM - 11:57AM |
M13.00006: Possible evidence for Lorentz Invariance Violation in GRB 221009A Justin D Finke, Soebur Razzaque The preliminary detections of the gamma-ray burst 221009A up to 18 TeV by LHAASO and up to 251 TeV by Carpet 2 have been reported through Astronomer's Telegrams and Gamma-ray Coordination Network circulars. Since this burst is at redshift z = 0.1505, these photons may at first seem to have a low probability to avoid pair production off of background radiation fields and survive to reach detectors on Earth. By extrapolating the reported 0.1 − 1.0 GeV LAT spectrum from this burst to higher energies and using this to limit the intrinsic spectrum of the burst, we show that the survival of the 18 TeV photon detected by LHAASO is not unlikely with many recent extragalactic background light models, although the detection of a 251 TeV event is still very unlikely. This can be resolved if Lorentz invariance is violated at an energy scale E_QG ? 49E_Planck in the linear (n = 1) case, and EQG ? 10−6E_Planck in the quadratic (n = 2) case (95% confidence limits), where E_Planck is the Planck energy. This could potentially be the first evidence for subluminal Lorentz invariance violation. |
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