Seminar:- The Non-thermal Universe, Cherenkov Astronomy, and the MAGIC Experiment
The universe is filled with highly relativistic particles and photons which acquire their energies in non-thermal processes, in the most violent astrophysical environments. High Energy(HE, E>100 MeV) and Very High Energy(VHE, E>100 GeV) gamma rays are produced in objects such as exploding stars, gamma-ray bursts(GRBs), near supermassive black holes, Active Galactic Nuclei(AGN), or pulsars.
VHE photons cannot be observed directly from Earth, since they are “absorbed” by the atmosphere, but in the last half century, indirect observation techniques of such gamma rays have been developed. Cherenkov Astronomy refers to the type of astronomy carried out by ground-based observatories that use the Cherenkov emission produced by VHE photons as they pass through the atmosphere. MAGIC is one such observatory. It is a stereoscopic system of two 17-meter diameter Imaging Atmospheric Cherenkov Telescopes(IACTs) located at about 2,200 m above sea level, in La Palma, Canary Islands, Spain.
In order to detect pulsars, high redshift AGN, and GRBs with IACTs, it is crucial to achieve an energy threshold well below 50 GeV, and a high sensitivity in the region below 100 GeV. In recent years, in order to optimise the performance at these energies, a new stereoscopic analog trigger, called Sum-Trigger-II, was developed and installed in MAGIC. The preliminary studies, using the Crab Nebula, show an energy threshold of around 30 GeV, and an improved sensitivity in the low energy range.
In this talk, the speaker will give a brief introduction to Cherenkov Astronomy in general, and to MAGIC in particular. She will then present some recent performance results of MAGIC using the Sum-Trigger-II and discuss future prospects for astrophysics in the 30-100 GeV range.
時間：2018.11.21(三) 16:00
地點：香港大學 莊月明物理樓522室
講者：Jezabel Garcia(Max Planck Institute for Physics, Munich, Germany)
語言：英語
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此活動由香港大學物理系主辦。
