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Suttiwat Madlee - Earth’s gamma-ray emission in geographical coordinates with Fermi-LAT data
Toggle Cloak Cloak The Earth’s gamma ray emission is produced from the interactions between cosmic rays (CRs), high-energy particles in space, and the Earth’s upper atmosphere. These gamma rays are measured by the Large Area telescope (LAT), the instrument onboard the Fermi Gamma-ray Space Telescope (Fermi) which was launched in 2008 to orbit the Earth at the altitude of ~540 km. Here we present preliminary results of the Earth’s gamma-ray intensity, which for the first time has been analyzed in geographical coordinates, using the latest version of LAT data. This study will provide better understanding of the geomagnetic field, the Earth’s upper atmosphere, and CRs.
Carlo van Rensburg - Spatially-Dependent Modelling of Pulsar Wind Nebula G0.9+0.1
Toggle Cloak Cloak We present results from a leptonic emission code that models the spectral energy density of a pulsar wind nebula by solving a Fokker-Planck-type transport equation and calculating inverse Compton and synchrotron emissivities. We have created this time-dependent, multi-zone model to investigate changes in the particle spectrum as they traverse the pulsar wind nebula, by considering a time and spatially-dependent magnetic field, spatially-dependent bulk particle speed implying convection and adiabatic losses, diffusion, as well as radiative losses. Our code predicts the radiation spectrum at different positions in the nebula, yielding the surface brightness versus radius and the nebular size as function of energy. We compare our new model against more basic models using the observed spectrum of pulsar wind nebula G0.9+0.1, incorporating data from H.E.S.S. as well as radio and X-ray experiments. We show that simultaneously fitting the spectral energy density and the energy-dependent source size leads to more stringent constraints on several model parameters.
- Tyler Williamson - Title
- Laila Vleeschower
- Sheridan Lloyd
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Wednesday, June 7
Brent Limyansky - Analyzing Pulsar “Glitches” Using the Fermi LAT LAT
Toggle Cloak Cloak Pulsars are rapidly rotating neutron stars which produce pulsed emission across the electromagnetic spectrum. Abrupt and unpredictable changes in emission frequency are known as “glitches”. In young pulsars, theory predicts that glitches are the result of a starquake-induced change in geometry of the neutron star’s crust. These types of glitches have the potential to produce gravitational waves, although they are not believed to be detectable with current technology. In rotation-powered pulsars, glitches are believed to come from interactions between surface and interior regions of the neutron star. Glitches are challenging to observe with pointed instruments, as the time of their occurrence cannot be predicted. The Fermi LAT, which continually monitors over 200 gamma-ray pulsars, is not hindered in this manner and is therefore well suited to observation and study of glitches. In this project, I will examine previously detected pulsars over the full time range of the mission. Glitches will be identified and catalogued, with subsequent analysis having the potential to investigate the glitching mechanism, the nature of neutron star interiors, and glitches as a source of gravitational waves.
Tiffany Lewis - A First-Principles Radiative Transport Model for Steady-State Blazar Spectra
Toggle Cloak Cloak Blazars are luminous sources across the entire electromagnetic spectrum, but the spectral formation mechanisms in these sources are not well understood. We have developed a new model for blazar spectra in which we numerically integrate the first-principles electron transport equation to generate the electron number distribution with respect to energy. Our transport model considers shock acceleration, adiabatic expansion, stochastic acceleration due to MHD waves, Bohm diffusion, synchrotron radiation, and inverse-Compton radiation. We implement the full Klein-Nishina cross-section for interactions with photons from dust and 26 individual lines from the broad line region. We use the solution for the electron distribution to predict multi-wavelength SED spectra for 3C 279. This new self-consistent model provides an unprecedented view into the jet physics at play in this source, especially the relative strength of the shock and stochastic acceleration components and the size of the acceleration region. We show that our new Compton + synchrotron blazar model is the first to successfully fit the FermiLAT gamma-ray data for this source based on a first-principles physical calculation.
- Sambid Wasti - Title
- Hester Schutte
- Cori Fletcher
- Tiaan Bezuidenhout
- Tejaswita Sharma
- Isabella Mereu
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