Trigger notices (N1)
N1 notices correspond to the first notices published following a detection of a transient event. Only GRM and ECLAIRs can issue N1 notices (respectively N1e and N1g).
GRM (N1g)
The grm-trigger notice (Packet_Type = 201) is issued when at least 2
out of the 3 Gamma-Ray Detectors (GRDs) composing the GRM instrument are triggered.
If only 2 GRDs are triggered, only the trigger time and no localisation information is
specified in the <WhereWhen> element. In case of a 3 GRDs detection, localisation
information is provided but without any localisation error that cannot be computed
on-board. It is set to -1 in the notice but we expect systematics as large as few tens of
degrees.
In any case, to organise an effective follow-up, we recommend for now to consider GRM
detections in combination with other detections (e.g. from ECLAIRs or another mission),
and/or to wait the GRM specific GCN circular where a better estimate of the localisation,
computed on the ground, will be provided.
ECLAIRs (N1e)
The
eclairs-wakeup(Packet_Type = 202) report a clean detection of a new potential burst by ECLAIRs. This notice is issue after the detection meets some validation criteria or has been validated by an ECLAIRs expert.The
eclairs-catalog(Packet_Type = 203). Similar to theeclairs-wakeupnotice but with a detection on a flaring source of the on-board catalogue.
The localisation typical uncertainty is about 8 arcmin.
The publication of one of this notice indicates that a new alert sequence has been opened and
confirmation of the detection will be inspected by a burst advocate (BA). The alert sequence
is identified by the burst_id and will be used in all SVOM notices and
circulars refering to this event.
In case of an ECLAIRs detection, another notice with the same fields than the eclairs-wakeup
notice and a more accurate localisation is published within few minutes:
the
slewingnotice (Packet_Type = 204) if the burst is significant and a slew will be performed for an on-board follow-up by the MXT and VT instruments, orthe
not-slewingnotice (Packet_Type = 205), indicating either the detection did not pass the slew threshold (Slew_Status=not-requested) or the slew of the platform is not possible (Slew_Status=rejected).
These notices reported during the prompt phase of the burst allow a better localisation by ECLAIRs with a typical uncertainty narrowed to about 5 arcmin.
Warning
The grm-trigger notice can only be issued if GRM triggers first, as its trigger
capabilty is inhibited if ECLAIRs has already triggered.
Also, no slewing or not-slewing can be issued after a GRM only detection as
the SVOM spacecraft is by design only able to slew automatically on ECLAIRs request.
Each of these 5 notices contain additional information about the detection, listed in the table below:
VOEvent section |
Parameter |
Value |
Description |
|---|---|---|---|
<What> |
SNR |
float [sigma] |
signal to noise ratio in the reconstructed image by ECLAIRs |
Timescale |
float [s] |
Time window in which the burst was detected |
|
Time_Window_Start |
ISOtime in UTC |
Start time of the time window in which the burst was detected (corresponds to the trigger time in <WhereWhen>) |
|
Time_Window_End |
ISOtime in UTC |
End time of the time window in which the burst was detected |
|
Lower_energy_Bound |
float [keV] |
Energy range of the detection |
|
Upper_energy_Bound |
|||
Only for ECLAIRs: |
- CRT
- IMT
|
Type of the trigger:
- count-rate trigger (CRT): trigger on short timescale from 10ms to 20s
- image trigger (IMT): trigger on long timescale from 20s to 20min
|
|
Only for GRM: |
- 111
- 110
- 101
- 011
|
Trigger status the 3 GRDs. Each digit corresponds to one of the 3 GRDs. 1 means the GRD triggers, 0 not. |
|
<What> |
Only for eclairs-catalog: |
int |
Identifier of the source in the ECLAIRs on-board catalogue |
Source_Name |
Name of the source in the ECLAIRs on-board catalogue |
||
<What> |
Only for ECLAIRs: |
- not-requested
- rejected
- accepted
|
Slew status of the SVOM platform |