Genevieve Schroeder
Off-axis GRBs and Where to Find Them
Long-duration gamma-ray bursts (GRBs) are the most luminous explosions in the Universe, visible out to cosmological redshifts. Almost every spectroscopically confirmed supernova (SN) associated with a long GRB has been hydrogen and helium poor with broad lines (Ic-bl), indicating a stripped massive star progenitor with fast winds that produced a highly-collimated jet viewed on-axis. A critical prediction of this progenitor model is that there should be a large number of off-axis jets accompanying SNe Ic-bl - however, this has yet to be observationally confirmed. Additionally, if a GRB is observed moderately off-axis, it may result in a spectrally softer X-ray flash (XRFs), detectable with X-ray observatories such as Einstein Probe and SVOM. Radio observations of XRFs and SNe Ic-bl can reveal late rising afterglows as the jet spreads into the field of view, providing one of the best pieces of evidence for the off-axis GRB scenario.
Here, I will present recent results following up several candidate off-axis GRBs, including an XRF and a sample of radio loud SNe Ic-bl. Additionally, I will lay the path forward to detecting off-axis GRBs in the era of large transient surveys.
Dennis Lee
Errors in Galactic Dust Extinction Maps due to Polycyclic Aromatic Hydrocarbon Abundance
Accurate correction for extinction by Galactic interstellar dust is essential for studying the extragalactic sky. Polycyclic aromatic hydrocarbons (PAHs), in particular, are a prominent component of the dust. Representing the smallest dust grain constituents in the interstellar medium, these carbonaceous molecules play important roles in its thermodynamics and chemistry. In this talk, I will discuss the impact of variations in PAH abundance on dust extinction at optical wavelengths. Specifically, I will focus on the limitations of widely used far-infrared-emission-based dust extinction maps due to their
insensitivity to PAH abundance variations. Finally, I will describe how observations from SPHEREx of PAHs at near-infrared wavelengths are a promising way to overcome this limitation.
CIERA Astrophysics
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