Steps to reproduce: Go to any Source page, e.g. http://xmm-catalog.irap.omp.eu/detection/107295613010001
Open Detection image and event list tools
Try to extract fotons.
There will be eighter 500 error from server or infinite loading (more that 40 minutes).
Looks like that issue is reproducing on all sources. Appeared on 15.10.2018. On weekend before it worked well.
conf() function run after the fit returns the confidence levels. By default the levels are set to 1 sigma. You can do this as a default part of 'Fit Spectrum' button.