7.3.1. Need for Public Analysis Tools and Data

Polarization analysis is complex, and mistakes can easily lead to high levels of PD being measured. As the field is not yet mature and collaborations are small, every analysis has so far almost exclusively been performed using a tool developed for that specific data. This constant reinvention of the wheel not only allows for mistakes but more importantly results in instrument-specific analysis tools. Such tools are incapable of being applied to other data, and their performance is difficult to verify by a referee or other interested scientists. If, additionally, the code and the data are not public, as is often the case, and publications lack details on the analysis, then it remains nearly impossible to investigate discrepancies with other results.

What is therefore required, arguably more so than more measurements, is a standardized analysis method, which can be adapted to each polarimeter with a public code. Such tools, similar to those widely used in spectrometry such as Xspec [319] and 3 ML, would not only allow to understand any potential discrepancies but would also remove the need to reinvent the method by each new collaboration. Furthermore, if additional instrument data and responses exist publicly, it would remove the requirement to have an in-depth understanding of the instrument for being able to perform analysis. This would allow, similar to what happens in spectrometry, for experts in the field of data analysis and statistics to perform the analysis instead of only instrument experts as is now often the case, allowing for more detailed and innovative analyses to be performed.

A first step towards this was produced as part of the 3ML framework [320] for the analysis of the POLAR data. The developed tools aim to provide a framework in which the instrument response and the measurement data are combined to perform the polarization analysis in a transparent way that is usable by anyone. Both for the instrument response and the data format, a standardized format is proposed similar to that used in spectrometry, and the tool can therefore easily be adapted for other polarimeters. The tool has been used first to analyze GRB 170114A [104] in detail using POLAR data, and subsequently to produce the full GRB catalog published by POLAR [187]. The POLAR data used for this analysis is furthermore public https://www.astro.unige.ch/polar/grb-light-curves (accessed on 25 August 2014), allowing further analysis by anyone interested as well as to perform rigorous tests of the validity of the different POLAR results. The public data alone could, for example, already be used by the Astrosat CZTI collaboration using the tools used for the results in [188] to find if their tools provide consistent results are those published in [187]. Although not perfect, such a study would arguably progress the field further than the analysis of additional Astrosat CZTI or POLAR data by the collaborations themselves.
