H.E.S.S. observations of the Gamma-ray Binary LMC P3

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Context: The first extra-galactic gamma-ray binary, LMC P3, is a gammaray binary comprising of an unconfirmed compact object and an O-star and is located in the Large Magellanic Cloud. Initially discovered in Fermi-LAT data, it shows an orbital period of 10.3 days. H.E.S.S. has reported the detected Very High Energy (VHE) gamma-ray emission during only 20% of the orbit (Abdalla et al. 2018), between orbital phases 0.2 and 0.4, which roughly corresponds to the inferior conjunction of the compact object. Purpose: H.E.S.S. has continued the observations of this object since then. This work aims to produce a data analysis with a much deeper data set. The new data allowed for a more precise measurement of the location of the VHE gamma-ray peak along the orbit of the system to be made. Methods: Using LMC observations from the HESS array from 2003- 2022, a spectral and temporal analysis was conducted using the analysis package Gammapy. N 157B is used as a standard candle for a consistency check. The analysis incorporates the latest orbital solutions for the system. Results: The peak of the VHE emission was found at a phase 0.268 - 0.366, which with the current orbital solution, places this after inferior conjunction. Conclusions: The VHE light curve is better constrained w.r.t. the previous H.E.S.S. publication(Abdalla et al. 2018). The peak of emission is reduced from 20% to just under 10% of the orbital period. In-depth physical modelling is required to explain the physical origin of the VHE gamma-ray emission.
A research report submitted in fulfilment of the requirements for the degree of Master of Science to the Faculty of Science, School of Physics, University of the Witwatersrand, Johannesburg, 2023
Gammaray binary, Large magellanic cloud