STARITHM
GRB detected by Einstein Probe WXT with moderate significance
AI Summary
A gamma-ray burst (GRB) was observed by the WXT instrument on the Einstein Probe at UTC time 2026-09-17 09:37:45.999, with a net count rate of 0.03 counts/s in the energy range 0.5-4 keV and a signal-to-noise ratio of 7. No additional GCN Circulars have been issued yet.
Measurements
| Event | EP260917a |
|---|---|
| Event ID | 01709318047 |
| Source | Einstein Probe WXT |
| Alert type | GRB |
| Significance | medium |
| Trigger time (UTC) | Thu, 17 Sep 2026 09:37:45 GMT |
| Right ascension (J2000) | 335.1539° |
| Declination (J2000) | 9.4534° |
| Position error radius | 0.002777777777777778° (10.0″) |
| Position from | EP-FXT afterglow position, GCN 45646 |
| Image SNR | 7 |
| GCN notices | 1 |
| GCN circulars | 6 |
Every localisation reported in Circulars (2)
| Instrument | Of | Error | Circular |
|---|---|---|---|
| EP-WXT | burst | 2.0′ (90%) | GCN 45621 |
| EP-FXT | afterglow | 10.0″ (90%) | GCN 45646 |
Observations (36)
Values parsed from the Circular text; each row names its Circular.
| Time since trigger | Band | Value | Telescope | Circular |
|---|---|---|---|---|
| T+6 min | 0.5-4 keV | 5.55 ± 1.51 erg/s/cm^2 | Einstein Probe | GCN 45621 |
| T+6 min | 0.5-4 keV | 2.06 erg/s/cm^2 | Einstein Probe | GCN 45621 |
| T+17.8 h | r | > 24 AB mag (limit) | COLIBRÍ | GCN 45624 |
| T+17.8 h | z | > 22.5 AB mag (limit) | COLIBRÍ | GCN 45624 |
| T+18.0 h | VT_B | > 22.8 AB mag (limit) | SVOM/VT | GCN 45642 |
| T+18.0 h | VT_R | > 22.7 AB mag (limit) | SVOM/VT | GCN 45642 |
| T+18.3 h | J | > 19.6 AB mag (limit) | Palomar 1-m | GCN 45628 |
| T+24.0 h | C | > 17.3 mag (limit) | MASTER-Tavrida | GCN 45656 |
| T+24.0 h | C | > 17.2 mag (limit) | MASTER-Tavrida | GCN 45656 |
| T+24.0 h | C | > 17.3 mag (limit) | MASTER-Tavrida | GCN 45656 |
| T+25.0 h | 0.5-10 keV | 5.00e-14 erg/s/cm^2 | Einstein Probe (EP) | GCN 45646 |
| T+39.0 h | C | > 18.2 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+39.0 h | C | > 17.1 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+39.0 h | C | > 18 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+39.1 h | C | > 17.6 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+39.1 h | C | > 17.7 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+39.2 h | C | > 17.8 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+39.2 h | C | > 18 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+39.2 h | C | > 17.7 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+39.3 h | C | > 17 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+39.9 h | C | > 17.6 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+39.9 h | C | > 18.2 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+39.9 h | C | > 18.1 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+40.0 h | C | > 17.8 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+40.0 h | C | > 18 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+40.0 h | C | > 18.2 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+40.1 h | C | > 17.8 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+40.1 h | C | > 17.5 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+40.1 h | C | > 17.9 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+40.1 h | C | > 18 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+40.2 h | C | > 16.9 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+40.2 h | C | > 17.6 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+40.3 h | C | > 17.5 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+40.3 h | C | > 17.5 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+40.3 h | C | > 17.2 mag (limit) | MASTER-OAFA | GCN 45656 |
| T+40.4 h | C | > 15.8 mag (limit) | MASTER-OAFA | GCN 45656 |
Notices (1)
Einstein Probe WXT — GRB · Thu, 17 Sep 2026 09:37:45 GMT
GCN Circulars (6)
GCN-45656 — EP260917a
· Sun, 20 Sep 2026 10:09:33 GMT
The MASTER-Net telescopes in Russia and Argentina observed the error box of EP260917a, reporting upper magnitude limits up to 18.2. Observations began shortly after the trigger time, with no significant detections reported.
GCN-45646 — EP260917a
· Sat, 19 Sep 2026 15:44:15 GMT
nap
GCN-45642 — EP260917a
· Sat, 19 Sep 2026 09:03:02 GMT
The SVOM/VT telescope observed the field of EP260917a, starting 17.8 hours after the trigger, but did not detect any new optical sources within the error box. The 5-sigma upper limits for the non-detections were measured at >22.8 mag in the VT_B band and >22.7 mag in the VT_R band.
GCN-45628 — EP260917A
· Fri, 18 Sep 2026 11:37:34 GMT
nap
GCN-45624 — EP260917a
· Fri, 18 Sep 2026 07:22:39 GMT
The COLIBRÍ telescope observed the field of EP260917a and did not detect any new sources at the position of interest, setting upper limits of r > 24.0 and z > 22.5 magnitudes. This non-detection provides constraints on the optical emission from the event.
GCN-45621 — EP260917a
· Fri, 18 Sep 2026 05:31:07 GMT
The Einstein Probe's Wide-field X-ray Telescope detected an X-ray transient, EP260917a, on September 17, 2026. The event lasted approximately 1500 seconds and had a peak flux of about 2.06 × 10^(-9) erg/s/cm^2, with a photon index of 2.31.
AI summary generated Fri, 18 Sep 2026 04:40:53 GMT.