Are there more appropriate significance tests than others for correlating telescope data?

I am doing analysis on data from the XMM-Newton survey catalog and finding that a lot of the light sources are suspected to be bleed out from other bright sources in the same area of the telescope array.

I want to do a correlation analysis to determine if the light curves from each source are from the same source, but I'm not sure which test is appropriate. I'm not sure if the data counts as random, if it should be considered parameterized or non-parameterized, ect.

Considering using the Mann-Whitney U test, but really this is from a superficial understanding.