Preliminary Exam |
Events During the Week of October 6th through October 13th, 2024
Monday, October 7th, 2024
- Search for TeV Halos Using HAWC Data
- Time: 3:00 pm - 5:00 pm
- Place: 5280 Chamberlin Hall
- Speaker: Hongyi Wu, Physics PhD Graduate Student
- Abstract: Extended gamma-ray emission at TeV energies, known as TeV halos, has been observed around a few middle-aged isolated pulsars. It has been suggested that they may also be powered by millisecond pulsars (MSPs). Using data from the High Altitude Water Cherenkov (HAWC) Observatory, we searched for extended gamma-ray emission around 36 isolated middle-aged pulsars and 57 MSPs. Through a stacking analysis comparing TeV flux models against a background-only hypothesis, we identified TeV halo-like emission from isolated middle-aged pulsars at a significance level of 5.10σ, but found no significant emission from MSPs. The results imply that TeV halos may commonly exist around middle-aged pulsars, while MSPs are not as efficient in producing them. These findings provide a method to identify pulsars that are invisible to radio, X-ray, and GeV gamma-ray observations, and have significant implications for the physics interpretation of the Galactic center GeV excess and high-latitude Galactic diffuse emission. Future works including HAWC and Fermi-LAT data analysis around TeV halo sources will also be discussed.
- Host: Ke Fang
Tuesday, October 8th, 2024
- No events scheduled
Wednesday, October 9th, 2024
- Connecting Multimessenger Observations to Theory in Particle Astrophysics from GeV to EeV
- Time: 11:00 am - 1:00 pm
- Place: 5280 Chamberlin Hall or
- Speaker: Angelina Partenheimer, Physics PhD Graduate Student
- Abstract: In my preliminary exam, I will discuss my paper on ultrahigh energy cosmic rays from gamma-ray sources. Ultra-high-energy cosmic rays (UHECRs) are the highest-energy particles ever observed. While the sources producing UHECRs are still unknown, the Pierre Auger Observatory has detected a large-scale dipole anisotropy in the arrival directions of cosmic rays above 8 EeV. My project explores whether resolved gamma-ray sources can reproduce the Auger dipole. I find that in all cases, the simulated dipole has an amplitude significantly larger than that measured by Auger, implying that the resolved gamma-ray sources are insufficient to account for the population of sources producing the highest-energy cosmic rays. Next, I will discuss my recent project on prospects of detecting GeV transients with IceCube DeepCore and Upgrade. A wide variety of transient sources have been predicted to emit GeV neutrinos. In light of the upcoming IceCube-Upgrade, which will extend the IceCube detector’s sensitivity down to a few GeV, I survey a variety of transient source models and compare the predictions and detector sensitivities. Finally, I will briefly discuss my intended thesis work, which involves using anticipated UHE neutrino data from the Payload for Ultrahigh Energy Observations balloon experiment to constrain the UHECR proton composition.
- Host: Ke Fang
Thursday, October 10th, 2024
- No events scheduled
Friday, October 11th, 2024
- No events scheduled