strange auth.log behaviour

[emanuelebruno]

Hi to all,

I have bought one month ago a proxmox server from ovh. Now I have noticed that in auth.log it is full of these events:
[...]
Jul 15 06:25:40 xxxxxxxxxx CRON[364807]: pam_unix(cron:session): session closed for user root
Jul 15 06:26:01 xxxxxxxxxx CRON[365255]: pam_unix(cron:session): session opened for user root by (uid=0)
Jul 15 06:26:01 xxxxxxxxxx CRON[365255]: pam_unix(cron:session): session closed for user root
Jul 15 06:27:01 xxxxxxxxxx CRON[365478]: pam_unix(cron:session): session opened for user root by (uid=0)
Jul 15 06:27:01 xxxxxxxxxx CRON[365478]: pam_unix(cron:session): session closed for user root
Jul 15 06:28:01 xxxxxxxxxx CRON[365671]: pam_unix(cron:session): session opened for user root by (uid=0)
Jul 15 06:28:01 xxxxxxxxxx CRON[365671]: pam_unix(cron:session): session closed for user root
[...]

taking a look to "crontab -e" I verified that it is empty...

Doing the same with my proxmox personal server in my house, the crontab behaviour seems different:
[...]
Jul 15 16:17:01 proxmox CRON[133625]: pam_unix(cron:session): session opened for user root by (uid=0)
Jul 15 16:17:01 proxmox CRON[133625]: pam_unix(cron:session): session closed for user root
Jul 15 17:17:01 proxmox CRON[137953]: pam_unix(cron:session): session opened for user root by (uid=0)
Jul 15 17:17:01 proxmox CRON[137953]: pam_unix(cron:session): session closed for user root
Jul 15 18:17:01 proxmox CRON[142283]: pam_unix(cron:session): session opened for user root by (uid=0)
Jul 15 18:17:01 proxmox CRON[142283]: pam_unix(cron:session): session closed for user root
[...]
In the first case the intervall is every minute, in the second case the intervall is every hour...

Is there anybodoy can explain me that?