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Divergent Pointing at the Highest Energies with the ASTRI-MiniArray

Representative image for thesis Tutor: Chiara Righi - External contact: prof. Francesco Longo, University and INFN, Trieste (Send Email)
Lasting: 3 years. PhD thesis.

Abstract - The current generation of Imaging Atmospheric Cherenkov Telescopes (IACTs) shows the importance of gamma-ray astronomy for modern astrophysics.
This field focuses on the most energetic component of the electromagnetic spectrum, with energies in the range of ∼ 50 GeV to hundreds of TeV.
Gamma rays, due to their neutral charge, are not disturbed by deflection from magnetic fields in their journey across the Universe, and can be traced back through their incoming direction.
Thus, they can address the acceleration processes of high-energy particles close to their acceleration sites, and also answer some of the most fundamental physics issues, like the Lorentz invariance, the existence of axion-like particles or the mystery of Dark Matter.
The next generation ground-based observatory for gamma-ray astronomy at very-high energies is currently under construction.
ASTRI-MiniArray is a project led by the Italian "Istituto Nazionale di Astrofisica" (INAF) to build and operate a next-generation IACT observatory in the energy range between 1 TeV and 100 TeV and beyond.
It will be composed of 9 small-sized (∼ 4 meter in diameter) and large field-of-view (∼ 10 degrees) double-mirror telescopes equipped with silicon photo-multiplier cameras.
The full array will be operational within the next few years at the Observatorio del Teide (Tenerife, Spain). ASTRI-MiniArray will be the precursor of the Cherenkov Telescope array (CTA), the biggest project of IACT that will consist of two arrays of telescopes, a southern-hemisphere and a northern-hemisphere array.

One of the science topics of this new generation of IACTs is the surveys of a large portion of the sky that provide an immense service to the researchers community in several contexts i.e. as the multimessenger astronomy for the research of gravitational waves (GW) electromagnetic counterparts or the capability to detect transient events, such as Gamma Ray Bursts (GRBs).
Considering Cherenkov telescopes’ limited field of view (FoV), the time needed for those science projects is large. The limited duty cycle of about 1000 hours per year of imaging Cherenkov facilities is a strong motivation to try to reduce the observation time needed for the surveys.
The huge number of telescopes of new IACTs arrays with respect to existing instruments, will allow taking full advantage of new pointing modes in which telescopes point slightly offset from one another, like the divergent mode.
This pointing mode leads to an increase in the field of view of the sub-array of telescopes with competitive performance compared to normal pointing of the same sub-array.

This new approach is currently being investigated for the CTA array, but never studied for the ASTRI-MiniArray project; for this reason a depth study can be useful to improve the science with this Italian project that is already under construction.

This thesis is devoted to the improvement of the analysis of ASTRI in divergent mode and to study the performance of this modality for different array configurations and number of telescopes, in order to investigate if the performance is competitive compared to normal pointing.
This thesis will serve also as a benchmark for the usage of the Divergent mode for the Small Sized Telescopes of the CTA southern array.

A.Donini et al.
L.Gerard et al.
M. Szanecki et al.