GRB 261108D
GCN Circular 46211
Michael C. Davis (UMN), Tomas Ahumada (NOIRLab), and Michael Coughlin (UMN) report:
We observed the field of GRB 261108D, detected by SVOM/ECLAIRs (Zhang et al., GCN 46200), with the Dark Energy Camera (DECam) on the 4-m Blanco telescope at CTIO. Observations began on 2026-11-09 at 07:52:29 UTC (approximately 8.00 hours after the trigger) under program 2026B-398365 (PI Davis).
Observations consisted of 1x300 s exposures in each of the r and i bands. The images were reduced with the NOIRLab DECam Community Pipeline (Valdes et al. 2014). After performing PSF-matched image subtraction against pre-burst Legacy Surveys DR11 coadds (Dey et al. 2019), we detect the candidate counterpart reported by Passaleva et al., GCN 46210. Our difference-image position, RA, Dec (J2000) = 170.604125 deg, Dec = -77.631611 deg, is about 0.3" from the near-infrared position. Photometry is calibrated against Legacy Surveys DR11 field stars.
We measure the following AB magnitudes, not corrected for Galactic extinction:
| Start UT | T_mid - T0 | Filter | Exposure | Magnitude (AB) |
|---|---|---|---|---|
| 2026-11-09T07:52:29 | 0.3350 | r | 1x300s | 22.13 ± 0.09 |
| 2026-11-09T07:57:59 | 0.3388 | i | 1x300s | 21.56 ± 0.11 |
We encourage further monitoring to establish the source’s relationship to the burst.
We thank the CTIO and NOIRLab staff for their support during these observations.
GCN Circular 46210
N. Passaleva (U Rome), J. Durbak (UMD), O. Guiffreda (UMD), M. El Kabir (U Rome), E. Troja (U Rome), A. S. Kutyrev (NASA/GSFC), S. B. Cenko (NASA/GSFC)
We observed the field of GRB261108D detected by the SVOM/ECLAIRs (Zhang et al., GCN 46200) in J-band with PRIME telescope. Observations started ~2h after the trigger.
Following image subtraction using reference templates from the VISTA Hemisphere Survey (VHS; McMahon et al. 2013), we detect an uncatalogued source. The coordinates of the candidate counterpart are:
RA (J2000) = 11:22:25.08 (170.60452 deg)
Dec (J2000) = -77:37:53.7 (-77.63159 deg)
with a magnitude J~18.8 AB, calibrated using nearby stars of the VHS and not corrected for galactic extinction.
We note the presence of an underlying galaxy candidate at the same position in the Legacy Survey DR11 (Dey et al. 2019), with a photometric redshift of z ~ 0.6, which may represent the putative host galaxy of the burst.
Further multi-wavelength follow-up observations are strongly encouraged to confirm the nature of this transient and its association with GRB 261108D.
PRIME is a 1.8m telescope with 1.56 square degree FOV (0.5 arcsec/pixel) located in Sutherland, South Africa at the South African Astronomical Observatory (SAAO) (Kutyrev et al. 2023, Yama et al. 2023, Durbak et al. 2024).
We thank the Osaka University observers at PRIME and the staff at SAAO for their support with these observations.
GCN Circular 46200
Li Zhang (IHEP), Hatsune Goto (CEA/RIKEN), Wenjin Xie (NAOC), Wenlong Zhang (PMO), Wenjun Tan (PKU), report on behalf of the SVOM mission team:
At 2026-11-08T23:52:36 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 261108D (SVOM burst-id sb26110813).
The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.
The burst was only detected by the Count-Rate Trigger (CRT), which produced a sequence of 4 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 7.57 in the [5-20] keV energy band over a time window of 5.10 seconds starting at 2026-11-08T23:52:28.
The localization of the best alert is R.A., Dec. 170.8495, -77.4870 degrees:
R.A. (J2000) = 11h23m23.89s
Dec. (J2000) = -77d29m13.07s
with a 90% confidence level (C.L.) radius of 10.37 arcmin (including systematic error of 2 arcmin added in quadrature).
Due to the sun angle constraint, no immediate slew was performed on this burst.
No X-ray observation could be performed by SVOM/MXT for the time being.No optical observation could be performed by SVOM/VT for the time being.
The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE.
The Burst Advocate (BA) on shift for this alert is Wenjun Tan: tanwj@ihep.ac.cn.
Please contact the BA by email if you require additional information.