Dr. Atreyee Sinha

Traditionally, Cherenkov telescopes have operated as closed collaborations with proprietary data and software tools, making it difficult to perform joint analysis across instruments. With the advent of the Cherenkov Telescope Array as an open observatory, it is necessary to have open data formats and analysis tools to be shared across instruments. This led to the creation of the GammaAstroDataFormats (GADF) initiative and development of the Gammapy package. Gammapy is a community-developed, open source Python package built on Numpy, Scipy and Astropy using open FITS based data formats. It is used for the analysis of gamma-ray data of many instruments including Imaging Atmospheric Cherenkov Telescopes (IACT; eg: CTA, H.E.S.S. and MAGIC), Water Cherenkov Detectors (WCD; eg: HAWC), as well as space based observatories (eg: Fermi-LAT). Starting from event list and instrument response functions at the so called "Data Level 3", Gammapy provides pipelines for reduction of the input data to binned WCS, HEALPix or region based data structures, which can then be modelling using Poisson maximum likelihood fitting. Traditional and novel analysis methods are supported, enabling joint likelihood analysis for combined multi-instrument analysis. The first part of this talk will focus on the development and features of the Gammapy package. We will then use the developed tools on gamma ray data from the H.E.S.S. and Fermi-LAT instruments, leading to the detection of one the faintest supernovas (G312.04) at GeV energies, the discovery of a new pulsar wind nebula with H.E.S.S., and the first detection of a passive molecular cloud at very high energies, thus enabling a new method to probe the cosmic ray density in the Galaxy. Future potentials of the field of Cherenkov astronomy will be discussed at the end.