GRB 260915A: Long-duration GRB detected by SVOM with fading X-ray afterglow

AI Summary

SVOM/ECLAIRs detected GRB 260915A on 2026-09-15 at 01:12:03 UTC with a broad emission profile lasting ~167 seconds in the 4-120 keV band. The burst showed a power-law spectrum (α = -1.20 ± 0.05) with fluence of (2.6 ± 0.1)×10⁻⁶ erg/cm². SVOM/MXT localized an X-ray source at RA=8.1504°, Dec=8.2440° with 49.7 arcsec uncertainty. Subsequent observations by Einstein Probe and Swift-XRT detected a fading X-ray afterglow, but extensive optical/NIR follow-up from multiple facilities (VLT, GTC, LCO, NOT, REM, WINTER) yielded only non-detections down to limiting magnitudes of r~24.6 AB, suggesting either a high-redshift event or significant dust extinction.

Measurements

Notices (1)

SVOM — GRB · Tue, 15 Sep 2026 01:14:42 GMT

GCN Circulars (19)

GCN-45647 — GRB 260915A · Sat, 19 Sep 2026 16:40:08 GMT
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GCN-45623 — GRB 260915A · Fri, 18 Sep 2026 06:26:48 GMT
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GCN-45612 — GRB 260915A · Thu, 17 Sep 2026 12:22:19 GMT
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GCN-45600 — GRB 260915A · Thu, 17 Sep 2026 00:45:32 GMT
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GCN-45590 — GRB 260915A · Tue, 15 Sep 2026 22:26:28 GMT
Swift has initiated a Target of Opportunity (ToO) observation of the gamma-ray burst GRB 260915A, detected by SVOM/ECLAIRs. Automated and manual analyses of XRT data will be conducted to identify potential afterglow candidates, with results to be reported online and via GCN Circulars.

GCN-45589 — GRB 260915A · Tue, 15 Sep 2026 18:42:53 GMT
The SYSU 80cm infrared telescope observed the field of GRB 260915A approximately 13.4 to 16.7 hours after its detection by SVOM/Eclairs but did not detect any source within the error box of the reported source, down to a 5-sigma depth of J ~ 19.7 Vega mag. This non-detection is consistent with other reported non-detections.

GCN-45588 — GRB 260915A · Tue, 15 Sep 2026 15:55:57 GMT
The SVOM/C-GFT team observed the field of GRB 260915A and obtained follow-up imaging in g, r, and i bands, but no credible candidate was detected within the error box of the source. The upper limits for the optical bands were measured and found to be consistent with previous non-detections.

GCN-45587 — GRB 260915A · Tue, 15 Sep 2026 14:28:31 GMT
The Einstein Probe (EP) performed a follow-up observation of GRB 260915A, detecting two uncataloged X-ray sources within the error region identified by SVOM/ECLAIRs. Both sources showed no clear decay and were observed approximately 1.66 hours after the initial trigger.

GCN-45586 — GRB 260915A · Tue, 15 Sep 2026 13:53:44 GMT
The SVOM/VT team has refined early optical upper limits for GRB 260915A, providing non-detection measurements in the VT_B and VT_R bands, consistent with previous observations. The analysis indicates that the source remains undetected, with upper limits of 23.3 mag in VT_B and 23.2 mag in VT_R, not corrected for Galactic extinction.

GCN-45585 — GRB 260915A · Tue, 15 Sep 2026 13:23:06 GMT
The Einstein Probe (EP) performed a follow-up observation of GRB 260915A, detecting two uncataloged X-ray sources within the error region identified by SVOM/ECLAIRs. This observation, starting about 1.66 hours after the initial detection, provides crucial data for understanding the X-ray emissions associated with the gamma-ray burst.

GCN-45584 — GRB 260915A · Tue, 15 Sep 2026 12:24:58 GMT
Astronomers observed the field of GRB 260915A, a gamma-ray burst detected by SVOM/ECLAIRs, using the REM 60 cm robotic telescope at the ESO observatory of La Silla. Preliminary photometry did not detect any optical/NIR uncatalogued source down to 3-sigma limits of r > 18.3 (AB) and H > 14.5 (Vega), indicating the absence of a detectable optical counterpart within the specified time frames.

GCN-45581 — GRB 260915A · Tue, 15 Sep 2026 09:42:49 GMT
SVOM/VT performed observations of GRB 260915A, triggered by SVOM/ECLAIRs, and detected no uncatalogued sources within the error box of MXT. The optical upper limits suggest this could be a high-z GRB candidate, prompting a call for near-infrared follow-up observations.

GCN-45580 — GRB 260915A · Tue, 15 Sep 2026 08:54:06 GMT
The SVOM/COLIBRÍ (FM-GFT) telescope observed the field of GRB 260915A and did not detect any new optical source at the MXT position, setting upper limits of r > 23.12 and z > 21.76. This non-detection is consistent with previous reports and provides additional constraints on the optical emission of the gamma-ray burst.

GCN-45578 — GRB 260915A · Tue, 15 Sep 2026 08:26:48 GMT
The 10.4m GTC telescope was triggered to observe GRB 260915A, but no optical transient was detected within the error circle, with upper limits of r = 24.58 mag, i = 22.82 mag, and z = 23.71 mag. These non-detections are consistent with other reports from LCO, SVOM/VT, and NOT.

GCN-45577 — GRB 260915A · Tue, 15 Sep 2026 07:53:10 GMT
The Nordic Optical Telescope (NOT) observed the field of GRB 260915A, detected by SVOM/ECLAIRS, and found no uncatalogued optical transient within the error region, down to a limiting magnitude of z ~ 21.5. This non-detection is consistent with previous observations, indicating the absence of an optical counterpart to the gamma-ray burst.

GCN-45575 — GRB 260915A · Tue, 15 Sep 2026 05:00:39 GMT
The SVOM/VT telescope did not detect any uncatalogued optical sources within the localization region of GRB 260915A, with a 5-sigma upper limit of magnitude 21.5 in both VT_B and VT_R bands. This non-detection is consistent with previous reports and encourages further radio and infrared follow-up observations.

GCN-45574 — GRB 260915A · Tue, 15 Sep 2026 04:56:50 GMT
The Fermi GBM Targeted Search detected a transient event consistent with GRB 260915A, initially identified by SVOM ECLAIRs, with a false alarm rate of 8.3e-5 Hz and a Fermi MET of 811127526.517 s. The event was most significantly detected on a 32.768 s timescale with a normal GRB spectrum.

GCN-45573 — GRB 260915A · Tue, 15 Sep 2026 04:14:02 GMT
The SVOM mission team observed the field of GRB 260915A using the LCO 1m telescope at Cerro Tololo and Teide Observatories, but did not detect any new source within the error box. The upper limits for the optical observations were measured as r > 21.1 AB and z > 20.5 AB.

GCN-45570 — GRB 260915A · Tue, 15 Sep 2026 01:39:08 GMT
The SVOM mission detected a gamma-ray burst, GRB 260915A, on September 15, 2026, at 01:12:03 UTC. The burst was localized with a 90% confidence radius of 4.12 arcmin and was also detected by SVOM/GRM with a significance of 8, leading to further observations by SVOM/MXT and VT.