Table 5.
Observational strategies of following up pre-merger alert events with CTA-LST.
| Time before merger | LST-a | LST-b | LST-c | LST-d | LST-e |
|---|---|---|---|---|---|
| 15 min | Event detected | Event detected with sky-loc < 103 deg2 | |||
| 14.5 min | Alert received | Alert received | |||
| 5 min | Event detected | Event detected with sky-loc < 103 deg2 | |||
| 4.5 min | Alert received | Alert received | |||
| 60 s | Event detected | Parameters updated | |||
| 30 s | Start slewing | Alert received +Start slewing | Start slewing | ||
| 10 s | Sky-loc reached | Sky-loc reached |
|||
| Repositioning on the updated sky-loc |
|||||
| Updated sky-loc reached | |||||
| Merger time | 20 s of exposure | ||||
| talert = 30 s | |||||
| Assumed time: | tslew = 20 s | ||||
| trep = 10 s | |||||
| texp = 20 s | |||||
| Total CTA time required: | tobs = 50 s | ||||
| Results | Fig. 8 (top row) | Fig. 8 (middle row) | Fig. 8 (bottom row) | Fig. 9 (top right plot) | Fig. 9 (bottom right plot) |
Notes. Taking into account the faster slewing of LST (tslew) with respect to MST, the slewing to reach the sky-localization starts 30 s before the merger in all the five strategies (LST-a, LST-b, LST-c, LST-d, LST-e). The alerts received at 14.5 before the merger are followed in the LST-a scenario, those received 4.5 min in LST-b, and those received 30 s before the merger in LST-c. Considering an alert time (talert) of 30 s, the 1 min alerts can also be followed up (LST-c). The last two columns show the scenarios LST-d and LST-e where the LST array follows up sky-localization smaller than 103 deg2 obtained at 15 and 5 min and then is re-positioned within the updated sky-localization obtained 1 min before the merger and received 30 s before the merger. The re-positioning time (trep) of 10 s has also been added to the total observation time for LST-a, LST-b, and LST-c to make the follow-up procedure safer. In the five cases described above the total CTA-LST time for one observation is 50 s.
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