Open Universe survey of Swift-XRT GRB fields: Flux-limited sample of HBL blazars
D'Elia, V.; Giommi, P.; Pollock, A. M. T.; Perri, M.; Puccetti, S.; Middei, R.; Padovani, P.; Barres de Almeida, U.; Verrecchia, F.; Capalbi, M.; Leto, C.; Sahakyan, N.; Turriziani, S.; Ruffini, R.; Brandt, C. H.; Chang, Y. L.; Glauch, T.; Penacchioni, A. V.; Arneodo, F.; Civitarese, O.; Di Giovanni, A.; De Angelis, M.; Del Rio Vera, J.; Di Pippo, S.; Ricard, N.
Germany, Italy, China, Russia, Argentina, United Arab Emirates, Brazil, Austria, United Kingdom, Armenia
Abstract
Aims: The sample of serendipitous sources detected in all Swift-XRT images pointing at gamma ray bursts (GRBs) constitutes the largest existing medium-deep survey of the X-ray sky. To build such dataset we analysed all Swift X-ray images centred on GRBs and observed over a period of 15 years using automatic tools that do not require any expertise in X-ray astronomy. Besides presenting a new large X-ray survey and a complete sample of blazars, this work aims to be a step in the direction of achieving the ultimate goal of the Open Universe Initiative, which is to enable non-expert people to benefit fully from space science data, possibly extending the potential for scientific discovery, which is currently confined within a small number of highly specialised teams, to a much larger population.
Methods: We used the Swift_deepsky Docker container encapsulated pipeline to build the largest existing flux-limited and unbiased sample of serendipitous X-ray sources. Swift_deepsky runs on any laptop or desktop computer with a modern operating system. The tool automatically downloads the data and the calibration files from the archives, runs the official Swift analysis software, and produces a number of results including images, the list of detected sources, X-ray fluxes, spectral energy distribution data, and spectral slope estimations.
Results: We used our source list to build the LogN-LogS of extra-galactic sources, which perfectly matches that estimated by other satellites. Combining our survey with multi-frequency data, we selected a complete radio-flux-density-limited sample of high energy peaked blazars (HBL). The LogN-LogS built with this data set confirms that previous samples are incomplete below ∼20 mJy.