Table 4.
Observational strategies of following up pre-merger alert events with CTA-MST.
| Time before merger | MST-a | MST-b | MST-c | MST-d |
|---|---|---|---|---|
| 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 | ||
| 100 s | Start slewing | |||
| 60 s | Parameters updated | |||
| 30 s | Updates received | |||
| 10 s | Sky-loc reached | 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 = 90 s | |||
| trep = 10 s | ||||
| texp = 20 s | ||||
| Total CTA time required: | tobs = 120 s | |||
| Results | Fig. 7 (top row) | Fig. 7 (bottom row) | Fig. 9 (top left plot) | Fig. 9 (bottom left plot) |
Notes. For all the strategies shown (MST-a, MST-b, MST-c, MST-d), MST starts slewing to the sky-localization at about 100 s before the merger time, following the alerts and parameters received at 14.5 min (MST-a and MST-c) or 4.5 min (MST-b and MST-d) before the merger. In the MST-c and MST-d scenarios the updated sky-localization estimated 1 min before the merger is used to re-position the MST array in about 10 s. In the MST-c and MST-d scenarios, we follow up only sky-localizations smaller than 103deg2 estimated 15 and 5 min before the merger, respectively. The table gives the values assumed for the time to detect, transmit, and receive the alert (talert), for the MST slewing time tslew, for the MST re-positioning time trep, and for the MST exposure time (texp). In all four strategies the total CTA-MST time necessary for a one-shot observation is 120 s.
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