Fermi GBM detects long GRB 260708A with significant X-ray and optical counterparts

AI Summary

Fermi GBM detected a long GRB 260708A on July 8, 2026, with a likely astrophysical origin. Follow-up observations revealed an X-ray counterpart with a slowly decaying emission and an optical counterpart showing significant fading.

Measurements

Notices (1)

Fermi GBM — GRB · Wed, 08 Jul 2026 10:11:16 GMT

GCN Circulars (12)

GCN-45150 — GRB 260708A · Tue, 14 Jul 2026 02:48:42 GMT
The EP/FXT observatory detected a slowly decaying X-ray source associated with the long GRB 260708A, with observations showing a consistent X-ray position and spectral characteristics over two follow-up sessions. The temporal decay index of the X-ray emission suggests a slow evolution, prompting a recommendation for optical spectroscopy to classify the source.

GCN-45147 — GRB 260708A · Mon, 13 Jul 2026 14:05:35 GMT
The GRANDMA collaboration observed the optical afterglow of GRB 260708A, detected by MASTER, using multiple telescopes and noted a softer decay than typical for GRBs. The observations were part of the P7 campaign to monitor fast transients and the data is available on the Skyportal/ICARE service.

GCN-45140 — GRB 260708A · Sun, 12 Jul 2026 05:22:33 GMT
The LCO 1m telescope at Cerro Tololo Inter-American Observatory detected the optical counterpart of GRB 260708A, which was initially identified by Fermi/GBM and Fermi/LAT. The observations, taken in SDSS g, r, and i filters, showed the source fading over time compared to previous reports.

GCN-45130 — GRB 260708A · Fri, 10 Jul 2026 11:25:29 GMT
The Glowbug gamma-ray telescope on the International Space Station detected GRB 260708A, a gamma-ray burst also observed by Fermi/GBM, Fermi/LAT, and GECAM-B, with a duration of 12.3 seconds and a significance of 7.7 sigma. The burst was the brightest portion of the light curves detected by other telescopes, indicating a significant astronomical event.

GCN-45127 — GRB 260708A · Thu, 09 Jul 2026 17:01:32 GMT
The GRANDMA/Kilonova-Catcher collaboration detected the optical afterglow of the gamma-ray burst GRB 260708A using the iTtelescope T30 at Siding Spring Observatory, confirming it as the optical counterpart reported by MASTER. The observation, made at 1.18 days post-burst, showed significant fading, indicating it is the afterglow of the energetic burst.

GCN-45126 — GRB 260708A · Thu, 09 Jul 2026 16:35:09 GMT
GECAM-B detected a gamma-ray burst, GRB 260708A, on July 8, 2026, at 10:11:17.650 UTC, which was also observed by Fermi/GBM and Fermi/LAT. The burst consisted of multiple pulses with a duration of approximately 46.5 seconds.

GCN-45124 — GRB 260708A · Thu, 09 Jul 2026 15:29:24 GMT
On July 8, 2026, the Fermi Gamma-ray Burst Monitor (GBM) detected GRB 260708A, a gamma-ray burst with a duration of 62 seconds and a peak photon flux of 19.6 ph/s/cm^2. The event was also detected by Fermi-LAT, and preliminary spectral analysis indicates a power law index of -1.86.

GCN-45123 — GRB 260708A · Thu, 09 Jul 2026 10:23:14 GMT
The MASTER Global Robotic Net detected an optical counterpart, MASTER OT J150237.02-435307.7, for the gamma-ray burst (GRB) 260708A, discovered by Fermi LAT. The optical transient was identified at magnitude 17.6, and its light curve characteristics suggest it is a GRB source, indicating the need for further spectral observations.

GCN-45119 — GRB260708 · Wed, 08 Jul 2026 22:55:59 GMT
The MASTER-OAFA robotic telescope in Argentina observed the error box of LAT GRB260708.42, a gamma-ray burst, starting 44,923 seconds after the trigger time, with upper magnitude limits up to 18.6. Observations began at twilight with a zenith distance of 25 degrees and a sun altitude of -11.4 degrees.

GCN-45118 — GRB260708B · Wed, 08 Jul 2026 18:52:03 GMT
The MAXI/GSC nova alert system detected a bright, uncatalogued X-ray transient source on July 8, 2026, at 16:43:12 UT. The source had an X-ray flux of 172 ± 25 mCrab in the 4.0-10.0 keV range and was located at (R.A., Dec) = (22h 48m 33s, -03° 46' 33'').

GCN-45117 — GRB 260708A · Wed, 08 Jul 2026 17:20:47 GMT
On July 8th, 2026, the Fermi-LAT detected high-energy emission from GRB 260708A, which was also observed by Fermi-GBM. The event showed a significant increase in event rate with a photon flux above 100 MeV of (1.9 ± 0.4)E-5 ph/cm2/s and the highest energy photon detected was 2.1 GeV.

GCN-45115 — GRB 260708A · Wed, 08 Jul 2026 14:17:47 GMT
The Fermi Gamma-ray Burst Monitor (GBM) detected a likely long gamma-ray burst (GRB 260708A) on July 8, 2026, at 10:11:16.89 UT. The event was located at RA = 227.4, Dec = -44.5 (J2000) with a statistical uncertainty of 1.6 degrees.