Hunting for black holes: a citizen science exploration of the X-ray transient sky

In the framework of the EU funded scientific project EXTraS, we develop an education activity which was run in several workshops for high school students in Italy, Germany and UK, lasting from 30 to 80 hours each. The work foresees: a) the extraction of transient candidates through the algorithm implemented by EXTraS team; b) the validation procedure of the candidates; c) the counterpart research; d) a final discussion about the results. We adopt an Inquiry-based learning strategy, together with a peer-to-peer education approach. This global strategy both fosters the critical thinking and engages the students, who act as though they were researchers. The workshops were run in a very informal environment. The students can be divided into different groups of 3-4 people or act as individuals. The leading questions of our inquiry are the following, each of them representing a step for further investigations of the data: 1) Is the transient candidate a real transient X-ray source? 2) Is it a new X-ray source? 3) Has it a possible counterpart at other wavelengths (e.g. optical)? 4) What kind of astrophysical object or phenomenon might it be? 5) Might it be an important scientific discovery?