Session T08: Gamma-ray Bursts and Supernovae

The Search for >100 GeV Photons from Gamma Ray Bursts with HAWC

To date, no photons above 100 GeV have been detected from a Gamma-Ray Burst (GRB). The detection or improved limits on this high energy emission would play an important role in constraining GRB emission models. The High Altitude Water Cherenkov (HAWC) observatory is well suited to study GRB spectra above 100 GeV; it is sensitive to the extensive air showers produced by ~0.1-100 TeV photons, and with its large instantaneous field of view (~2sr) and high duty cycle HAWC is capable of observing the prompt emission of tens of GRBs per year. We present the results of recent efforts to enhance HAWC's 0.1-1 TeV sensitivity through improvements to its extensive air shower reconstruction algorithms and discuss their impact on HAWC's analysis of the >100 GeV gamma-ray emission of known GRBs.   

Fermi Observations of High Energy Emission from GRB 190114C

Synchrotron radiation from shock accelerated electrons has been well established as the source of the broadband afterglow emission accompanying gamma-ray bursts (GRBs). The relativistic electrons producing this emission are expected to also produce synchrotron self-compton (SSC) emission, yet no convincing evidence has ever been found for such an emission component.  Late-time detections at GeV energies by the Fermi Large Area Telescocpe (LAT) have been shown to be consistent with the high energy extension of afterglow emission, without the need for SSC to explain most LAT detections. The detection of very high energy emission in GRB 190114C by Fermi LAT and MAGIC is now the first conclusive detection of this elusive emission component and may shed further light on the physics of GRB afterglows.  We will review the Fermi Gamma-ray Burst Monitor (GBM) and LAT observations of GRB 190114C and discuss their implications for relativistic shock physics, future very high energy observatories, and possible constraints on the extra-galactic background light.   

Detect Supernova Neutrinos with DarkSide-20k LAr TPC

Simulations of core collapse supernovae have undergone great progress in the last decade, yet detections of supernova neutrinos are needed to test these theoretical models. The neutronization burst has yet to be observed; the mechanism that triggers the explosion needs to be tested by observation. In addition, core collapse supernovae provide opportunities to study some fundamental properties of neutrinos, including its absolute mass and mass hierarchy. We report here that DarkSide-20k LAr TPC can play an important and unique role in such observation. It detects neutrinos via coherent elastic neutrino nucleus scattering (CEvNS) which is neutral current interaction and flavor blind. For a typical supernova at a distance of 10 kpc, the 39 tonne LAr TPC can detect about 200 - 300 neutrino events. The supernova neutrino spectrum and the total energy emitted can be measured independent of flavor oscillation. The background level in DarkSide-20k LAr TPC is low, allowing good sensitivity for many measurements.