Yes, they look like latex log files (first line says "This is XeTeX, Version 3.14159265-2.6-0.99998 (TeX Live 2017) (preloaded format=xelatex 2017.5.23)") and they are staying in the working directory after the script finishes running. It used to be the case tat they are removed afterward, but not now. I wonder now if that's because there are numerous warnings of the type:
"Package microtype Warning: Unknown slot number of character
(microtype) \~A' (microtype) in font encoding TU' in inheritance list
(microtype) `microtype.cfg/358(protrusion)'.
"
I don't actually use the microtype package, so I couldn't figure it out, but maybe that's the way to dig to get rid of these log files. thank you!