Gary Finnegan Thesis Defense 08/22/12

Thesis Defense

Gary Finnegan

Monday, August 22, 2012
2:00pm (110 INSCC)

Title: High Energy Gamma-Ray Astronomy Observations Of Geminga With The VERITAS Array


The closest known super-nova remnant and pulsar is Geminga. The Geminga pulsar is the first pulsar to have ever been detected initially by gamma rays and the first pulsar in a class of radio-quiet pulsars. In 2007 a detection of very high energy gamma rays (∼ 20 TeV), that are positionally coincident with Geminga, was reported by the Milagro collaboration, with a large angularly extended emission (∼ 2.6° ). The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is a ground- based observatory with four imaging Cherenkov telescopes with an energy range between 100 GeV to more than 30 TeV. The imaging Cherenkov telescopes detect the Cherenkov light from charged particles in an electromagnetic air shower initiated by high energy particles such as gamma rays and cosmic rays. The field of view (FOV) of the VERITAS telescopes is approximately 3.5°. Most gamma-ray sources detected by VERITAS are point like sources, which have an angular extension smaller than the resolution of the telescopes (∼ 0.1°). For an angularly extended object, such as Geminga, an external FOV from the source must be used to estimate the background noise to avoid contamination from the source itself. In this dissertation, I will describe a new analysis procedure that is designed to increase the sensitivity of angularly extended objects like Geminga. I will present the results of my analysis, which conclude with the detection of very high energy emission from the Geminga region at the level of a few percent of the Crab nebula and a possible extension less than one degree wide. This detection however awaits a confirmation by the VERITAS collaboration. To conclude, I will present the implications of the detection of Geminga.


[1] G. Finnegan for the VERITAS Collaboration, ”Orbit Mode Observation Technique Developed for VERITAS”, Proceedings of the 2011 Fermi Symposium, arXiv:1111.0121v1 (Nov 2011).

[2] G. Finnegan for the VERITAS Collaboration, “Search for TeV Emission from Geminga by VERITAS”, Proceeding of the 31st ICRC, arXiv:0907.5237v3 (July 2009).

[3] V.A. Acciari, et al, “Observation of Extended Very High Energy Emission from the Supernova Remnant 1C443 with VERITAS”, Astrophysical Journal Letters 698, L133 (2009).

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