GCN Circulars
GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search
To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.
Advanced Search Examples (click to copy):
subject:"Swift"body:"GRB"submitter:"Judith Racusin"12008 results found.
- GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
- GRB 260822A: LCO optical upper limits
- GRB260822B: Fermi GBM Final Localization
- Fermi-LAT Gamma-ray Observations of IceCube-260821A
- Fermi-LAT Gamma-ray Observations of IceCube-260807A
- IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
- GRB 260818B: VLA radio observations
- EP detected a brightening of LMXB 1ES 1735-26.9
- GRB260820A: Fermi GBM Final Real-Time Localization
- GRB 260818B: SVOM/ECLAIRs refined analysis
- EP260806a: SAO RAS multicolor optical observations
- EP260806a: SVOM/ECLAIRs detection through targeted search
- EP260812b: Optical upper limit with Kinder
- EP260812a: NOT and Liverpool Telescope upper limits:
- EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
- EP260812b: Einstein Probe detection of an X-ray transient
- EP trigger #01709278129 (EP260812b?): NOT optical counterpart
- GRB 260810A: AstroSat CZTI detection of a long burst
- EP260812a: Einstein Probe detection of an X-ray transient
- GRB 260809A: SAO RAS optical observations
- GRB 260807A: SVOM/ECLAIRs refined analysis
- GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
- GRB 260808B: SVOM/ECLAIRs refined analysis
- EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
- GRB 260808B: LCO optical observations
- GRB 260808A: NuSTAR detection of prompt emission
- EP260809a: COLIBRÍ optical observations
- EP260809a: Einstein Probe detection of an X-ray transient
- GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
- GRB 260808B: SVOM/VT optical candidate from VHF data
- GRB 260808B: SVOM detection of a faint burst
- GRB 260807A: SVOM possible detection of a faint burst
- EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
- EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
- EP260806a: Einstein Probe detection of an X-ray transient
- SN 2026stf / GRB 260708A: ATLAS forced photometry
- Fermi GRB 260802B: Global MASTER-Net observations report
- GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
- GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
- GRB 260731A: AstroSat CZTI detection of a long burst
- Fermi-LAT Gamma-ray Observations of IceCube-260722A
- GRB 260730B: AstroSat CZTI detection
- EP260731a: Einstein Probe detection of an X-ray transient
- EP260729a: Einstein Probe detection of an X-ray transient
- EP260727a: SAO RAS optical observations
- EP260728a: Einstein Probe detection of a fast X-ray transient
- EP260727a:refined analysis of the EP-WXT and EP-FXT observation
- Konus-Wind detection of GRB 260727A
- EP260727a: Einstein Probe detection of an X-ray transient
- GRB 260727A: AstroSat CZTI detection
- EP260723a: further EP-FXT follow-up observation
- EP260725a: EP-WXT detection of an X-ray transient
- EP260723a: EP-WXT detection of a fast X-ray transient
- Konus-Wind detection of GRB 260721A
- Konus-Wind detection of GRB 260714B
- GRB 260705A: Retraction of optical counterpart
- Fermi trigger No 806104130: Global MASTER-Net observations report
- Fermi GRB 260718A: Global MASTER-Net observations report
- GRB 260718A: SVOM detection of a burst
- sb26071506: SVOM detection of a X-ray transient
- GRB 260710A: AstroSat CZTI detection
- GRB 260709A: AstroSat CZTI detection
- GRB 260714B: AstroSat CZTI detection
- GRB 260714B: Fermi-LAT detection
- IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
- EP260713a: Einstein Probe detection of an X-ray transient
- Fermi-LAT Gamma-ray Observations of IceCube-260712A
- Fermi-LAT Gamma-ray Observations of IceCube-260708A
- Fermi-LAT Gamma-ray Observations of IceCube-260704A
- EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
- GRB 260705C: AstroSat CZTI detection
- GRB 260706A : GRANDMA Upper limits
- IceCube-260708A: One candidate from the Zwicky Transient Facility
- GRB260708B: MAXI/GSC detection
- GRB 260708A: Fermi-LAT detection
- EP260707a: LCOGT Optical Upper Limit
- EP260707a: Einstein Probe detection of an X-ray transient
- GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
- The EP-WXT trigger 01709274141 is likely a flaring star
- IPN triangulation of GRB 260627A
- GRB 260706A: SVOM detection of a burst
- GRB 260629A: AstroSat CZTI detection
- GRB 260704A: SVOM detection of a possible GRB
- EP260703a: EP-WXT detection of a fast X-ray transient
- EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
- Fermi GRB 260703A: Global MASTER-Net observations report
- GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
- Fermi trigger No 804552016: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-260622A
- EP260628a: EP-WXT detection of a fast X-ray transient
- Konus-Wind detection of GRB 260623B / EP260623a
- EP260623a: FTW optical and NIR observations
- Konus-Wind detection of GRB 260618B
- EP260623a:refined analysis of the EP-WXT and EP-FXT observation
- EP260623a: Optical follow-up observations with Kinder
- EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
- EP260623a: Einstein Probe detection of an X-ray transient
- GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
- GRB 260618B: LCO optical observations
- GRB 260618B: Fermi GBM Observation