PostgreSQL messages in security log - SOLVED

I’ve read in previous posts that these messages are harmless and normal, but what are they, where are they coming from, why every 15 minutes? I previously had Postgresql disable and have now enable it - just for these messages…

Jun 26 09:55:02 host1 su: pam_unix(su:session): session opened for user postgres by (uid=0)
Jun 26 09:55:02 host1 su: pam_unix(su:session): session closed for user postgres
Jun 26 10:00:02 host1 su: pam_unix(su:session): session opened for user postgres by (uid=0)
Jun 26 10:00:02 host1 su: pam_unix(su:session): session closed for user postgres
Jun 26 10:05:02 host1 su: pam_unix(su:session): session opened for user postgres by (uid=0)
Jun 26 10:05:02 host1 su: pam_unix(su:session): session closed for user postgres

I found the answer in this post…

https://www.virtualmin.com/node/11194