GRB 260515A: Long-duration gamma-ray burst with z=0.764 optical counterpart

AI Summary

SVOM/ECLAIRs detected GRB 260515A on May 15, 2026 at 19:08:19 UTC with a 16.6-second duration and SNR of 24.06 in the 5-20 keV band. The burst showed a FRED-like light curve with a faint hard precursor, with a time-averaged photon index of -1.69 and fluence of 1.09×10⁻⁶ erg/cm². The optical counterpart was rapidly identified and spectroscopically confirmed at redshift z=0.764 using GTC/OSIRIS+. Multi-wavelength follow-up observations tracked the optical afterglow decay over weeks, with late-time detections at ~23 days post-trigger showing continued fading, consistent with a standard long GRB afterglow.

Measurements

Notices (1)

SVOM — GRB · Fri, 15 May 2026 19:08:19 GMT

GCN Circulars (28)

GCN-44898 — GRB 260515A · Wed, 10 Jun 2026 20:40:46 GMT
The GRB 260515A event was observed using the SOAR Telescope, confirming late-time optical emission approximately 23 days after the initial trigger. The measurements, taken in SDSS r and i filters, detected a magnitude of 23.1 in the i-band, with a 5-sigma magnitude limit of 23.6 in the r-band, indicating potential contributions from the host galaxy.

GCN-44821 — GRB 260515A · Thu, 04 Jun 2026 15:44:09 GMT
The SVOM/VT telescope detected the optical counterpart of GRB 260515A about 18 days after the initial trigger, with a faint detection in the VT_R band and an upper limit in the VT_B band. This follow-up observation provides additional data on the afterglow of the gamma-ray burst, which was initially detected by SVOM/ECLAIRs and Konus-Wind.

GCN-44820 — GRB 260603A · Thu, 04 Jun 2026 12:05:46 GMT
The optical afterglow of the gamma-ray burst GRB 260603A was observed using the Nordic Optical Telescope (NOT) with an AB magnitude of 23.27 in the SDSS r band, detected 0.786 days after the trigger. The observation was calibrated against nearby stars from the Pan-STARRS catalog and was not corrected for Galactic extinction.

GCN-44819 — GRB 260603A · Thu, 04 Jun 2026 09:46:23 GMT
The Simeiz Zeiss-1000 telescope observed the field of GRB 260603A approximately 0.6 days after the trigger but did not detect the optical afterglow, setting a preliminary upper limit of magnitude 22.3 in the R-filter. The observations were conducted using a series of 20x180 second exposures and photometry based on nearby USNO-B1.0 stars.

GCN-44805 — GRB 260603A · Wed, 03 Jun 2026 14:21:26 GMT
The Einstein Probe (EP) performed a follow-up observation of GRB 260603A, detecting an uncatalogued source consistent with an optical counterpart. The source's spectrum was fitted with an absorbed power-law model, revealing a photon index of 2.4 and an unabsorbed flux of 4.0 × 10^-12 erg/s/cm^2 in the 0.5-10 keV band.

GCN-44800 — GRB 260603A · Wed, 03 Jun 2026 12:36:36 GMT
The GRANDMA/Kilonova-Catcher collaboration observed the field of GRB 260603A using the T11 itelescope but did not detect the optical counterpart reported by SVOM/COLIBRÍ and SVOM/VT, setting an upper limit magnitude of 20.1 in the r filter. This non-detection is significant for understanding the nature and characteristics of the transient event.

GCN-44799 — GRB 260603A · Wed, 03 Jun 2026 12:00:59 GMT
The SVOM/VT telescope detected the optical counterpart of GRB 260603A in both VT_B and VT_R channels, with measurements showing a fading slope of about -0.53. The observations started approximately 1.44 hours post-trigger and continued to monitor the fading light of the gamma-ray burst.

GCN-44797 — GRB 260603A · Wed, 03 Jun 2026 10:00:53 GMT
The SVOM/ECLAIRs GRB 260603A was observed using the COLIBRÍ telescope, revealing a candidate counterpart with a photometric redshift of z = 3.57. The counterpart has continued to fade, and spectroscopic observations are encouraged to confirm the findings.

GCN-44791 — GRB 260603A · Wed, 03 Jun 2026 06:54:17 GMT
An uncatalogued optical source, potentially the counterpart of GRB 260603A, was detected by the SVOM/COLIBRÍ telescope with preliminary magnitudes r = 19.78 ± 0.01 and z = 19.27 ± 0.01. The source was observed to brighten and then fade, suggesting it is associated with the gamma-ray burst.

GCN-44787 — GRB 260603A · Wed, 03 Jun 2026 06:28:01 GMT
The SVOM mission detected a gamma-ray burst, GRB 260603A, on June 3, 2026, at 05:38:16 UTC. The burst was located at R.A. 15h32m32.79s and Dec. 40d04m48.22s with a 90% confidence level radius of 5.42 arcmin.

GCN-44666 — GRB 260515A · Tue, 19 May 2026 14:14:04 GMT
The SVOM/ECLAIRs instrument detected GRB 260515A, a gamma-ray burst with a FRED-like light curve and a faint hard precursor, lasting approximately 16.33 seconds. The event was also observed by Konus-Wind, and the time-averaged spectrum was best fitted by a power-law model with a photon index of -1.69.

GCN-44658 — GRB 260515A · Sun, 17 May 2026 08:10:40 GMT
The Liverpool Telescope observed the field of GRB 260515A using the IO:O optical camera, detecting a source in both SDSS r and i filters approximately 5.55 hours after the initial trigger. The photometry measurements were calibrated using nearby PanSTARRS secondary standards, with magnitudes of 21.32 ± 0.06 in the r filter and 21.26 ± 0.07 in the i filter.

GCN-44652 — GRB 260515A · Sat, 16 May 2026 23:52:00 GMT
The field of GRB 260515A was observed using the Shajn 2.6-meter telescope at the Crimean Astrophysical Observatory, with optical transient (OT) detected in stacked frames. Photometry data in BVRI filters were obtained starting about 3 hours after the trigger, providing detailed measurements of the OT's brightness and characteristics.

GCN-44647 — GRB 260515A · Sat, 16 May 2026 19:07:11 GMT
The Konus-Wind satellite detected a long-duration gamma-ray burst, GRB 260515A, on May 15, 2026, with a significant count rate increase and a fluence of 7.70 x 10^-6 erg/cm^2. The burst's isotropic energy release and peak luminosity are estimated to be 1.25 x 10^52 erg and 5.70 x 10^50 erg/s, respectively, consistent with known relations for long GRBs.

GCN-44646 — GRB 260515A · Sat, 16 May 2026 14:32:40 GMT
The Liverpool Telescope detected the optical counterpart of GRB 260515A approximately 3.57 hours after the burst, measuring an AB magnitude of g = 21.06 ± 0.04 in the SDSS g filter. This detection was part of a collaborative effort involving multiple institutions and telescopes.

GCN-44645 — GRB 260515A · Sat, 16 May 2026 14:16:15 GMT
The optical counterpart of the gamma-ray burst GRB 260515A has been detected using the Las Cumbres Observatory 1-m telescope, with a redshift of 0.764 and an AB magnitude of r' = 20.32. This detection follows observations from SVOM/ECLAIRs and Einstein Probe FXT, confirming the presence of the optical transient.

GCN-44643 — GRB 260515A · Sat, 16 May 2026 11:06:13 GMT
The SVOM/COLIBRÍ telescope observed the field of GRB 260515A, detecting a source with preliminary magnitudes r = 21.78 ± 0.02 and z = 21.50 ± 0.05, approximately 13.3 hours after the initial trigger. The observations were conducted using the DDRAGO imager with simultaneous exposure in r and z filters, calibrated with nearby stars from the PanSTARRS DR1 catalog.

GCN-44642 — GRB 260515A · Sat, 16 May 2026 09:39:53 GMT
The Einstein Probe (EP) performed a follow-up observation of GRB 260515A, detected by SVOM/ECLAIRs, identifying a fading X-ray source consistent with optical counterparts. The source's spectrum was fitted with an absorbed power-law model, yielding a photon index of 1.71 and an unabsorbed flux of 7.13 x 10^(-12) erg/s/cm^2 in the 0.3-10 keV band.

GCN-44634 — GRB 260515A · Sat, 16 May 2026 03:45:58 GMT
The SVOM/VT telescope detected the optical counterpart of GRB 260515A in both VT_B and VT_R bands, with a redshift of z=0.764. Observations started 155 seconds post-trigger and continued for 1.85 hours, showing a change in the decay slope from 1.3 to 0.8.

GCN-44633 — GRB 260515A · Sat, 16 May 2026 03:39:29 GMT
The optical counterpart of GRB 260515A was observed using the T193cm telescope at Observatoire de Haute-Provence, with preliminary magnitudes of r = 20.42 +/- 0.13 mag and r = 21.34 +/- 0.12 mag during two epochs. The observations were conducted 2.36 hours and 5.04 hours after the initial trigger, providing valuable data on the afterglow of the gamma-ray burst.

GCN-44629 — GRB 260515A · Sat, 16 May 2026 01:11:21 GMT
The optical counterpart of GRB 260515A was observed using the Gran Telescopio Canarias (GTC) equipped with the OSIRIS+ instrument, revealing a spectroscopic redshift of z = 0.764. This redshift was determined from metal absorption features and an [O II] emission doublet, confirming the distance and properties of the gamma-ray burst.

GCN-44628 — GRB 260515A · Sat, 16 May 2026 00:11:51 GMT
The SVOM/ECLAIRs GRB 260515A was observed using the LCO 1m telescope at Teide Observatory, detecting a faint optical counterpart with magnitudes r = 21.22 +/- 0.09 AB and z > 20.5 AB. The observations were conducted approximately 3.57 hours after the initial trigger, providing valuable follow-up data on the gamma-ray burst event.

GCN-44627 — GRB 260515A · Fri, 15 May 2026 21:53:05 GMT
The MASTER-Tavrida robotic telescope in Russia was pointed to the SVOM GRB 260515A error box 30 seconds after notice time and 659 seconds after trigger time, with observations beginning at a zenith distance of 32 degrees and a sun altitude of -18.8 degrees. The observations provided upper limits up to 19.9 magnitude in the C filter, with multiple measurements taken over a period of several hours.

GCN-44626 — GRB 260515A · Fri, 15 May 2026 21:31:23 GMT
The optical counterpart of GRB 260515A was observed using the Nordic Optical Telescope (NOT) with the ALFOSC instrument, detecting an optical afterglow with an AB magnitude of r = 20.22. This observation was part of a collaborative effort involving multiple institutions and was calibrated against the Pan-STARRS catalog.

GCN-44625 — GRB 260515A · Fri, 15 May 2026 20:41:12 GMT
The MASTER-Tavrida robotic telescope detected an optical transient, MASTER OT J151044.43+243321.7, with a magnitude of 17.4, associated with the gamma-ray burst SVOM GRB 260515A. This detection is significant as it provides an optical counterpart to the gamma-ray event, aiding in further spectral observations.

GCN-44624 — GRB 260515A · Fri, 15 May 2026 20:26:50 GMT
The SVOM satellite detected an optical candidate for the gamma-ray burst GRB 260515A, identified as VT_ID 32 with coordinates RA 15h10m44.4s and Dec 24d33m22.4s. This detection is consistent with an optical afterglow reported by He et al. and has magnitudes of 16.16 ± 0.01 in VT_B and 15.78 ± 0.01 in VT_R, suggesting a redshift z < 4.

GCN-44623 — GRB 260515A · Fri, 15 May 2026 19:51:51 GMT
A new optical counterpart candidate for GRB 260515A has been detected using the JinShan 100B telescope, located in Altay, Xinjiang, China. The source, with coordinates R.A. 227.6852 deg and Dec. 24.5562 deg, is uncatalogued and varying, with a magnitude of approximately 16.5 in the Sloan i-band.

GCN-44622 — GRB 260515A · Fri, 15 May 2026 19:36:12 GMT
The SVOM satellite detected a gamma-ray burst, GRB 260515A, on May 15, 2026, with a duration of 16.6 seconds and a significance of 10.2. The burst was localized to coordinates RA 15h10m43.20s, Dec 24d34m14.13s with a 90% confidence radius of 3.77 arcminutes.