adjusting the threshold on trigger duration to avoid contamination by long GRBs

[JunTian-CIRA]

The threshold on trigger duration has been set to 2.048s for Fermi GRBs. I investigated the trigger duration of all the GRBs detected by Fermi last year, and found the 2.048s threshold is unlikely to exclude long GRBs. From the plot attached, it can be seen if we set the threshold to be 0.512s, we may expect 9GRBs (30% is short) to be observed during the 2020A semester. This GRB number is consistent with the goal in our proposal (8). Therefore, I suggest to change the threshold on trigger duration from 2.048s to 0.512s.

For Swift GRBs I suggest to trigger on all of them for now as the Swift detects much fewer GRBs than Fermi. Moreover, the accurate localisation of Swift GRBs makes the data analysis much handier. The VCS trigger on Swift short GRBs is the focus of our research plan this year, so we must ensure there will be VCS data to process. After our first VCS trigger on Swift GRB, we can check the triggering parameters and adjust our strategy in the future.

[JunTian-CIRA]

A kind reminder that the new threshold on trigger duration has yet to be implemented.

[JunTian-CIRA]

A kind reminder that we are triggering on Fermi GRBs with trigger duration 2.048s. Please see the log file log_Fermi_610757949.txt

To reduce the contamination by long GRBs, we should turn down the threshold to 0.512s for all Fermi triggers. The threshold on swift triggers can be left as it is now.

[JunTian-CIRA]

Important update(!): Since I have requested to trigger on all Swift GRBs with VCS mode (see the ticket "triggering on all Swfit GRBs with VCS #17"), the new threshold should be applied only to Fermi GRBs, i.e. the threhsold on the trigger duration of Fermi GRBs should be reduced from 2.048s to 0.512s.