In an lsf environment (interactive or otherwise) if the application exceeds memory utilization beyond some preset threshold by the admins on the queue or the resource request in submit to the queue the processes will be killed so other users don't fall victim to a potential run away. It doesn't always send an email when it does so, depending on how its set up.
One solution in this case is to find a queue with larger resources or define larger resource requirements in the submission.
You may also want to review man ulimit
Although I don't remember ulimit resulting in Killed its been a while since I needed that.