I was receiving mail from cron that my bash script was returning error:
Interrupted by signal 15...
So i have searched this message at SE and found nothing.
Then i searched "linux bash signals" and found this where is shown that signal 15 is SIGTERM:

Table 12-2. Common kill signals
Signal name Signal value Effect
SIGHUP 1 Hangup
SIGINT 2 Interrupt from keyboard
SIGKILL 9 Kill signal
SIGTERM 15 Termination signal
SIGSTOP 17,19,23 Stop the process

just wanted to share this finding