Long-term X-ray light curve of eRASSU J060839.5−704014 for the 0.2−2 keV band. The mean value of all observations from eRASS1–4 is marked in red and our XMM-Newton pointed observation in blue. The two sources from the clean XMMSL2 catalogue are marked with a black “+”. The black “×” marks the slew observation that belongs to our XMM-Newton pointed observation. A black-body model with a temperature of 100 eV was used for flux conversion for the data from the upper limit server, i.e. for Einstein, ROSAT and XMM-Newton slew data. The 1σ errors are given for ROSAT and XMM-Newton slew data, and the Einstein upper limit is given with a 99.7% confidence level. Errors for XMM-Newton pointed and eROSITA data have 90% confidence intervals.