STARITHM
Long GRB 260610B detected by Fermi GBM with z=0.473 and optical rebrightening
AI Summary
Fermi GBM detected a long gamma-ray burst (GRB 260610B) on 2026-06-10 at 23:46:14.25 UT with T90 duration of ~62 seconds and localization at RA=218.66°, Dec=23.94° (error 2.77°). The burst spectrum is characterized by a power-law with exponential cutoff (Epeak=46.8±0.4 keV, fluence 1.30±0.02 × 10⁻⁵ erg/cm²). An optical counterpart (AT2026owq) was rapidly identified and spectroscopically confirmed at redshift z=0.473, with subsequent multi-wavelength observations revealing an unusual optical rebrightening ~5 days post-burst, potentially indicating late jet activity or an emerging supernova. Radio (VLA 9 GHz: 0.4 mJy) and millimeter (ALMA 43 GHz: 0.3 mJy) detections further constrain the afterglow properties.
Measurements
| Event | GRB 260610B |
|---|---|
| Event ID | 802827979 |
| Source | Fermi GBM |
| Alert type | GRB |
| Significance | high |
| Trigger time (UTC) | Wed, 10 Jun 2026 23:46:14 GMT |
| Right ascension (J2000) | 218.66° |
| Declination (J2000) | 23.94° |
| Position error radius | 2.77° (2.77°) |
| Position from | notice FERMI_GBM_FIN_POS |
| GCN notices | 7 |
| GCN circulars | 29 |
Every localisation reported in Circulars (1)
| Instrument | Of | Error | Circular |
|---|---|---|---|
| Fermi-GBM | burst | 2.77° (1-sigma statistical) | GCN 44901 |
Burst properties (15)
As each instrument's Circular reported them; values parsed from the Circular text.
| Property | Value | Band | Instrument | Spectral model | Circular |
|---|---|---|---|---|---|
| Duration | 65 ± 8 s | 15-5000 keV | SVOM/GRM | — | GCN 44944 |
| Duration | 62 s | 50-300 keV | GBM | — | GCN 44931 |
| Fluence | 9.48 1e-06 erg/cm^2 | 10-1000 keV | SVOM/GRM | cutoff_power_law | GCN 44944 |
| Fluence | 1.3 ± 0.02 1e-05 erg/cm^2 | 10-1000 keV | GBM | — | GCN 44931 |
| Peak flux | 3.98 1e-07 erg/cm^2/s | 10-1000 keV | SVOM/GRM | cutoff_power_law | GCN 44944 |
| Peak flux | 7.7 ± 0.3 ph/s/cm^2 | 10-1000 keV | GBM | — | GCN 44931 |
| Photon index | -1.59 | 10-1000 keV | SVOM/GRM | cutoff_power_law | GCN 44944 |
| Photon index | -1.62 | 10-1000 keV | SVOM/GRM | cutoff_power_law | GCN 44944 |
| Photon index | -1.5 ± 0.01 | 10-1000 keV | GBM | cutoff_power_law | GCN 44931 |
| Photon index | -1.48 ± 0.0009 | 10-1000 keV | GBM | band | GCN 44931 |
| Photon index | -3.17 ± 0.01 | 10-1000 keV | GBM | band | GCN 44931 |
| Epeak | 34 keV | 10-1000 keV | SVOM/GRM | cutoff_power_law | GCN 44944 |
| Epeak | 25 keV | 10-1000 keV | SVOM/GRM | cutoff_power_law | GCN 44944 |
| Epeak | 46.8 ± 0.4 keV | 10-1000 keV | GBM | cutoff_power_law | GCN 44931 |
| Epeak | 45.9 ± 0.5 keV | 10-1000 keV | GBM | band | GCN 44931 |
Observations (72)
Values parsed from the Circular text; each row names its Circular.
| Time since trigger | Band | Value | Telescope | Circular |
|---|---|---|---|---|
| T+-140364 s | o | > 19.45 mag (limit) | ZTF, ATLAS | GCN 44903 |
| T+-495 s | w | > 20.35 AB mag (limit) | ATLAS-Teide | GCN 44910 |
| T+-456 s | w | > 20.2 AB mag (limit) | ATLAS-Teide | GCN 44910 |
| T+8 min | w | 16.26 ± 0.02 AB mag | ATLAS-Teide | GCN 44910 |
| T+12 min | L | 16.66 ± 0.01 AB mag | GOTO | GCN 44903 |
| T+19 min | w | 16.29 ± 0.02 AB mag | ATLAS-Teide | GCN 44910 |
| T+86 min | L | 17.83 ± 0.03 AB mag | GOTO | GCN 44903 |
| T+2.8 h | g | 18.85 AB mag | Nordic Optical Telescope (NOT) | GCN 44914 |
| T+2.8 h | r | 18.4 AB mag | Nordic Optical Telescope (NOT) | GCN 44914 |
| T+2.9 h | i | 18.14 AB mag | Nordic Optical Telescope (NOT) | GCN 44914 |
| T+2.9 h | z | 17.92 AB mag | Nordic Optical Telescope (NOT) | GCN 44914 |
| T+3.3 h | g | 19 AB mag | Nordic Optical Telescope (NOT) | GCN 44914 |
| T+3.3 h | r | 18.49 AB mag | Nordic Optical Telescope (NOT) | GCN 44914 |
| T+3.3 h | i | 18.25 AB mag | Nordic Optical Telescope (NOT) | GCN 44914 |
| T+3.3 h | z | 18.04 AB mag | Nordic Optical Telescope (NOT) | GCN 44914 |
| T+5.1 h | w | 18.82 ± 0.04 AB mag | DDOTI | GCN 44905 |
| T+7.1 h | g | 19.48 ± 0.1 AB mag | COLIBRÍ | GCN 44911 |
| T+7.1 h | r | 19.02 ± 0.03 AB mag | COLIBRÍ | GCN 44911 |
| T+7.1 h | i | 18.61 ± 0.11 AB mag | COLIBRÍ | GCN 44911 |
| T+7.1 h | z | 18.54 ± 0.08 AB mag | COLIBRÍ | GCN 44911 |
| T+7.1 h | y | 18.25 ± 0.28 AB mag | COLIBRÍ | GCN 44911 |
| T+8.6 h | R | 18.92 ± 0.05 mag | 0.7-m telescope | GCN 44909 |
| T+22.0 h | Rc | 19.14 ± 0.16 AB mag | 0.5-m T1 | GCN 44920 |
| T+22.0 h | Ic | 18.88 ± 0.16 AB mag | 0.5-m T1 | GCN 44920 |
| T+22.3 h | Rc | 19.85 ± 0.06 mag | 0.82m IAC80 | GCN 44919 |
| T+22.4 h | SDSS-r | 20.04 ± 0.06 mag | 0.82m IAC80 | GCN 44919 |
| T+22.4 h | Ic | 19.23 ± 0.05 mag | 0.82m IAC80 | GCN 44919 |
| T+22.5 h | B | 20.94 ± 0.13 mag | 0.82m IAC80 | GCN 44919 |
| T+25.6 h | B | 21.47 ± 0.26 mag | 0.82m IAC80 | GCN 44919 |
| T+25.7 h | V | 20.35 ± 0.09 mag | 0.82m IAC80 | GCN 44919 |
| T+25.8 h | Ic | 19.4 ± 0.08 mag | 0.82m IAC80 | GCN 44919 |
| T+25.9 h | SDSS-r | 20.26 ± 0.09 mag | 0.82m IAC80 | GCN 44919 |
| T+33.7 h | Rc | 19.73 ± 0.03 mag | Zeiss-1000 1-m | GCN 44918 |
| T+33.7 h | Rc | > 22.6 mag (limit) | Zeiss-1000 1-m | GCN 44918 |
| T+35.7 h | R | 19.81 ± 0.06 mag | Zeiss-2000 2-meter telescope | GCN 44946 |
| T+35.7 h | R | > 22.4 mag (limit) | Zeiss-2000 2-meter telescope | GCN 44946 |
| T+45.3 h | R | 20.59 ± 0.1 mag | AS-32 70-cm | GCN 44977 |
| T+45.3 h | R | > 22 mag (limit) | AS-32 70-cm | GCN 44977 |
| T+2.1 d | r | 21.05 ± 0.07 AB mag | 2m robotic Liverpool Telescope | GCN 44932 |
| T+2.1 d | i | 20.61 ± 0.09 AB mag | 2m robotic Liverpool Telescope | GCN 44932 |
| T+2.1 d | z | 20.28 ± 0.12 AB mag | 2m robotic Liverpool Telescope | GCN 44932 |
| T+2.1 d | g | 21.4 ± 0.14 AB mag | 2m robotic Liverpool Telescope | GCN 44932 |
| T+2.4 d | R | 20.7 ± 0.13 mag | Zeiss-2000 2-meter telescope | GCN 44946 |
| T+2.4 d | R | > 22.3 mag (limit) | Zeiss-2000 2-meter telescope | GCN 44946 |
| T+2.4 d | Rc | 20.61 ± 0.03 mag | Zeiss-1000 1-m | GCN 44929 |
| T+2.4 d | Rc | > 23.5 mag (limit) | Zeiss-1000 1-m | GCN 44929 |
| T+2.6 d | 43 GHz | 0.3 mJy | ALMA | GCN 44941 |
| T+2.9 d | 9 GHz | 0.4 mJy | Karl G. Jansky Very Large Array (VLA) | GCN 45065 |
| T+4.0 d | r | 21.34 ± 0.07 AB mag | Liverpool Telescope | GCN 44959 |
| T+4.0 d | g | 21.71 ± 0.07 AB mag | Liverpool Telescope | GCN 44959 |
| T+4.6 d | Rc | 21.14 ± 0.12 mag | Zeiss-1000 1-m | GCN 44963 |
| T+4.6 d | Rc | > 22.3 mag (limit) | Zeiss-1000 1-m | GCN 44963 |
| T+5.1 d | g | 21.49 ± 0.08 AB mag | Liverpool Telescope | GCN 44959 |
| T+5.1 d | r | 21.02 ± 0.07 AB mag | Liverpool Telescope | GCN 44959 |
| T+5.3 d | g | 21.52 ± 0.13 AB mag | COLIBRÍ | GCN 44958 |
| T+5.3 d | r | 21.02 ± 0.1 AB mag | COLIBRÍ | GCN 44958 |
| T+5.3 d | i | 20.69 ± 0.09 AB mag | COLIBRÍ | GCN 44958 |
| T+5.3 d | z | 20.43 ± 0.1 AB mag | COLIBRÍ | GCN 44958 |
| T+5.6 d | Rc | 20.98 ± 0.17 mag | Zeiss-1000 1-m | GCN 44963 |
| T+5.6 d | Rc | > 21.8 mag (limit) | Zeiss-1000 1-m | GCN 44963 |
| T+6.0 d | r | 20 AB mag | ESO Very Large Telescope (VLT) UT1 (Antu) | GCN 45004 |
| T+6.5 d | Rc | 21.06 ± 0.18 mag | Zeiss-1000 1-m | GCN 44963 |
| T+6.5 d | Rc | > 21.9 mag (limit) | Zeiss-1000 1-m | GCN 44963 |
| — | r | 21.31 ± 0.1 AB mag | Fraunhofer Telescope at Wendelstein Observatory (FTW) | GCN 44981 |
| — | g | 21.7 ± 0.2 AB mag | Pan-STARRS | GCN 44955 |
| — | r | 21.2 ± 0.1 AB mag | Pan-STARRS | GCN 44955 |
| — | i | 20.9 ± 0.1 AB mag | Pan-STARRS | GCN 44955 |
| — | z | 20.7 ± 0.2 AB mag | Pan-STARRS | GCN 44955 |
| — | g | 21.8 ± 0.3 AB mag | Pan-STARRS | GCN 44955 |
| — | r | 21.3 ± 0.2 AB mag | Pan-STARRS | GCN 44955 |
| — | i | 20.7 ± 0.2 AB mag | Pan-STARRS | GCN 44955 |
| — | z | 20.6 ± 0.2 AB mag | Pan-STARRS | GCN 44955 |
Notices (1)
Fermi GBM — GRB · Wed, 10 Jun 2026 23:46:14 GMT
GCN Circulars (29)
GCN-45065 — GRB 260610B
· Thu, 02 Jul 2026 20:07:05 GMT
The Very Large Array (VLA) has detected a radio counterpart to the gamma-ray burst GRB 260610B at a frequency of 9 GHz with a flux density of approximately 0.4 mJy. This detection is consistent with previously reported optical and radio positions, and further observations are planned.
GCN-45062 — GRB 260610B
· Wed, 01 Jul 2026 08:35:23 GMT
Further optical observations of GRB 260610B, detected by the Fermi GBM team, were conducted using multiple telescopes from June 17 to June 27, revealing a brightening phase around 5 days after the initial trigger, which might indicate a supernova. The optical transient (OT) was clearly detected in stacked images, with a preliminary light curve showing slow fading until the 15th day.
GCN-45007 — GRB 260610B
· Fri, 19 Jun 2026 15:24:48 GMT
The GRANDMA collaboration has continued observing the optical afterglow of the Fermi Long GRB 260610B, detecting a re-brightening consistent with other reported measurements. The observations are part of the P7 campaign to monitor alerts from explosive fast transients.
GCN-45004 — GRB 260610B
· Fri, 19 Jun 2026 14:42:59 GMT
Spectroscopic observations of GRB 260610B using the VLT/FORS2 spectrograph suggest that the optical rebrightening is due to late jet activity, indicating a non-thermal nature. The observations also confirm the redshift of the event at z = 0.474 and hint at the possible emergence of a supernova.
GCN-44993 — GRB 260610B
· Fri, 19 Jun 2026 10:18:21 GMT
The 1.3m Devasthal Fast Optical Telescope (DFOT) detected an optical rebrightening of the gamma-ray burst GRB 260610B/AT2026owq, which was initially discovered by the Fermi Gamma-ray Burst Monitor. The observation, conducted approximately 4.73 days after the initial trigger, revealed a preliminary magnitude of 20.88 in the R filter, consistent with previous detections by other observers.
GCN-44981 — GRB 260610B
· Thu, 18 Jun 2026 19:32:02 GMT
The afterglow of GRB 260610B (AT 2026owq) was observed using the Three Channel Imager at the Fraunhofer Telescope at Wendelstein Observatory, detecting a rebrightening/flattening in multiple bands, with a measured magnitude of 21.31 in the r-band. This observation is part of ongoing follow-up studies on the gamma-ray burst event.
GCN-44977 — GRB 260610B
· Thu, 18 Jun 2026 10:47:10 GMT
The Abastumani Astrophysical Observatory (AbAO) detected an optical transient (OT) associated with the gamma-ray burst GRB 260610B using the AS-32 70-cm telescope, with a magnitude of 20.59 in the R-band. The observation was made 1.856 days after the initial trigger, and the photometry was based on nearby SDSS stars, though not corrected for Galactic extinction.
GCN-44963 — GRB 260610B
· Wed, 17 Jun 2026 09:33:10 GMT
Observations of GRB 260610B by the Zeiss-1000 1-m telescope of SAO RAS suggest a possible re-brightening or plateau in the afterglow light curve. The optical transient (OT) was detected with varying magnitudes over June 14, 15, and 16, 2026.
GCN-44959 — GRB 260610B
· Tue, 16 Jun 2026 20:04:25 GMT
The Liverpool Telescope has confirmed the continuing optical rebrightening of GRB 260610B, with measurements indicating an achromatic rebrightening episode beyond 5 days after the initial trigger, inconsistent with expectations for an emerging supernova.
GCN-44958 — GRB 260610B
· Tue, 16 Jun 2026 19:58:21 GMT
The optical counterpart of GRB 260610B, AT 2026owq, was reimaged using the COLIBRÍ telescope, confirming a rebrightening/flattening event observed approximately 80 hours after the initial trigger. The source was detected with preliminary magnitudes of g = 21.52, r = 21.02, i = 20.69, and z = 20.43, consistent with previous observations.
GCN-44955 — GRB 260610B
· Tue, 16 Jun 2026 15:30:51 GMT
The optical counterpart to GRB 260610B, AT 2026owq, has shown signs of re-brightening or flattening in its light curve across all observed filters (griz) according to Pan-STARRS observations. This behavior is unusual for a typical GRB-supernova signal and warrants further investigation.
GCN-44946 — GRB 260610B
· Mon, 15 Jun 2026 08:46:27 GMT
The field of GRB 260610B was observed using the Zeiss-2000 2-meter telescope at the Terskol Observatory on June 11 and 12, 2026. The optical transient (OT) was detected with R-band magnitudes of 19.81 and 20.70 on these dates, respectively.
GCN-44944 — GRB 260610B
· Mon, 15 Jun 2026 08:36:29 GMT
The SVOM/GRM instrument detected a gamma-ray burst (GRB 260610B) on June 10, 2026, at 23:46:14.100 UTC, which was also observed by Fermi/GBM. The burst had a T90 duration of 65.0 ± 8.0 seconds and a measured redshift of 0.473, indicating it is a Type II GRB consistent with the 'Amati' relation.
GCN-44941 — GRB 260610B
· Sun, 14 Jun 2026 21:57:00 GMT
The Atacama Large Millimeter/Submillimeter Array (ALMA) detected a millimeter source with a flux density of approximately 0.3 mJy associated with GRB 260610B, consistent with previously reported optical positions. This detection occurred 2.62 days after the initial burst and further observations are planned.
GCN-44932 — GRB 260610B
· Sat, 13 Jun 2026 19:36:46 GMT
The Liverpool Telescope conducted optical observations of the gamma-ray burst GRB 260610B, detecting a source in all filters at the reported position approximately 2.07 days after the initial trigger. The photometry data was obtained using the IO:O optical camera and calibrated with nearby PanSTARRS secondary standards.
GCN-44931 — GRB 260610B
· Sat, 13 Jun 2026 18:21:44 GMT
On June 10, 2026, the Fermi Gamma-ray Burst Monitor detected GRB 260610B, a gamma-ray burst with a duration of 62 seconds and a redshift of 0.473. The event was also observed optically by GOTO, and its spectrum was characterized by a power law with an exponential cutoff.
GCN-44930 — GRB 260610B
· Sat, 13 Jun 2026 13:50:34 GMT
The GRANDMA collaboration detected the optical afterglow of the long Gamma-Ray Burst (GRB) 260610B, observed by the Fermi satellite, using multiple telescopes around the world. The observations, part of the P7 campaign, are consistent with other reported measurements and are available for public access through the ACME service Skyportal/ICARE.
GCN-44929 — GRB 260610B
· Sat, 13 Jun 2026 06:35:11 GMT
The optical transient (OT) associated with the gamma-ray burst GRB 260610B, detected by the Fermi satellite, was observed using the Zeiss-1000 1-m telescope at SAO RAS. The OT was clearly detected with a magnitude of 20.61 in the Rc filter, and this preliminary photometry was based on nearby SDSS stars.
GCN-44921 — GRB 260610B
· Fri, 12 Jun 2026 08:27:15 GMT
The SVOM/VT telescope detected an optical transient (OT) associated with GRB 260610B in both VT_B and VT_R bands, approximately 13.32 hours after the initial trigger. The OT was measured with magnitudes of 20.10 +/-0.06 mag in VT_B and 19.38 +/-0.06 mag in VT_R at the first observation point.
GCN-44920 — GRB 260610B
· Fri, 12 Jun 2026 07:54:38 GMT
The optical counterpart of GRB 260610B, also known as AT2026owq, was observed using the 0.5-m T1 telescope at the Osservatorio Astronomico S. Di Giacomo in Agerola, Italy, starting approximately 0.917 days after the GRB trigger. The optical transient was clearly detected in both Rc and Ic filters with preliminary magnitudes of 19.14 +/- 0.16 mag and 18.88 +/- 0.16 mag, respectively.
GCN-44919 — GRB 260610B
· Fri, 12 Jun 2026 07:06:28 GMT
The optical afterglow of GRB 260610B was observed using the IAC80 telescope at Teide Observatory, with photometry data collected over two nights. The preliminary photometry, calibrated relative to an SDSS star, provides detailed measurements in various filters, contributing to the understanding of the gamma-ray burst's afterglow characteristics.
GCN-44918 — GRB 260610B
· Thu, 11 Jun 2026 22:05:25 GMT
The GRB260610B event, detected by Fermi, was observed optically with the Zeiss-1000 1-m telescope at SAORAS, revealing an optical transient (OT) with a magnitude of 19.73 in the Rc filter. This detection is significant for studying the afterglow and properties of gamma-ray bursts.
GCN-44914 — GRB 260610B
· Thu, 11 Jun 2026 13:44:50 GMT
The optical counterpart of GRB260610B, identified as GOTO26fua/AT2026owq, has been observed with a spectroscopic redshift of z=0.473, indicating its distance and potential significance in understanding gamma-ray bursts. The observation was made using the Alhambra Faint Object Spectrograph (ALFOSC) on the Nordic Optical Telescope (NOT) as part of the GOTO-FAST program.
GCN-44911 — GRB 260610B
· Thu, 11 Jun 2026 11:14:07 GMT
The COLIBR telescope detected the optical counterpart AT2026owq of the Fermi GBM GRB260610B, with preliminary magnitudes in g, r, i, z, and y filters. The absence of a strong break in the five-filter measurements suggests a low-redshift event, and spectroscopic observations are encouraged due to its brightness.
GCN-44910 — GRB 260610B
· Thu, 11 Jun 2026 11:00:56 GMT
The ATLAS survey detected the optical counterpart AT2026owq of GRB260610B, with observations starting just 7.9 minutes post-explosion, providing early constraints on the event. The transient was first detected with a magnitude of 16.26 AB mag, and its proximity to nearby galaxies suggests potential low-redshift association.
GCN-44909 — GRB 260610B
· Thu, 11 Jun 2026 09:13:48 GMT
The Thai Robotic Telescope (TRT) in Fresno, California, observed the field of GRB 260610B, detected by Fermi, approximately 0.36 days post-burst. The optical counterpart was clearly detected with a brightness of R = 18.92, calibrated with Pan-STARRS DR2 stars, and not corrected for Galactic extinction.
GCN-44905 — GRB 260610B
· Thu, 11 Jun 2026 06:31:15 GMT
The field of GRB 260610B was observed using the DDOTI wide-field imager, detecting the candidate afterglow GOTO26fua/AT2026owq with a preliminary AB magnitude of 18.82 +/- 0.04, which continues to fade with a temporal decay index of approximately −0.6. This observation is consistent with previous measurements by O'Neill et al.
GCN-44903 — GRB 260610B
· Thu, 11 Jun 2026 02:49:52 GMT
The GOTO telescope network detected an optical counterpart candidate, GOTO26fua/AT2026owq, for the gamma-ray burst GRB260610B. The source, located at RA, DEC (J2000) = 218.159414, 27.004935, showed a decay consistent with a power-law index of t^-0.56, strongly suggesting it is the optical counterpart of the GRB.
GCN-44901 — GRB 260610B
· Thu, 11 Jun 2026 01:29:13 GMT
The Fermi Gamma-ray Burst Monitor (GBM) detected a likely long gamma-ray burst (GRB) designated GRB260610B on June 10, 2026, at 23:46:14.25 UT. The event was located at RA=218.66, Dec=23.94 (J2000) with a statistical uncertainty of 2.77 degrees. This detection is significant for studying high-energy astrophysical phenomena.
AI summary generated Thu, 05 Nov 2026 09:22:04 GMT.