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.
Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
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"- GRB 251222A: Swift ToO observations
- GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
- GRB 251222A: SVOM/VT optical candidate
- GRB 251222A: SVOM detection of a long burst
- SVOM GRB251222A: Global MASTER-Net observations report
- GRB 251222A: Fermi GBM Final Real-time Localization
- EP251220a: PRIME upper limit
- EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
- GRB 251221A: PRIME near-infrared observation
- EP251220a: NOT optical observations
- EP251220a: FTW optical and NIR observations
- GRB 251221A: UAFO and Mondy optical upper limit
- GRB 251221A: Swift-XRT refined Analysis
- EP251221a: Einstein Probe detection of a fast X-ray transient
- GRB 251221A: Swift/UVOT Upper Limits
- Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
- GRB 251221A: Enhanced Swift-XRT position
- GRB 251221A: Fermi GBM Observation
- GRB 251221B: Fermi GBM Final Real-time Localization
- EP251220a: EP-FXT follow-up observation
- GRB 251220B: SVOM/GRM observation of a short burst
- EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
- EP 251220a: GOTO optical counterpart detection
- GRB 251221A: COLIBRÍ detection of the optical counterpart
- EP 251220a: COLIBRÍ detection of the optical counterpart
- GRB 251221A: Swift detection of a burst
- Swift GRB251221A: Global MASTER-Net observations report
- GRB 251221A: Fermi GBM Final Real-time Localization
- EP251220a: Global MASTER-Net observations report
- EP251220a: EP detection of a fast X-ray transient
- SVOM GRB251220.98: Global MASTER-Net observations report
- GRB 251220B: Fermi GBM Final Real-time Localization
- GRB 251219A: SVOM/GRM observation of a short burst
- GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
- Fermi-LAT Gamma-ray Observations of IceCube-251218A
- GRB 251220A: MAXI/GSC detection
- GRB 251215A: Swift-XRT afterglow detection
- IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
- IceCube-251218A: COLIBRÍ optical upper limits
- SVOM GRB251219.11: Global MASTER-Net observations report
- IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
- IceCube Alert 251218.85: Global MASTER-Net observations report
- GRB 251214B: VIRT Optical Upper Limit
- Fermi trigger No 787736968: Global MASTER-Net observations report
- Fermi GRB 251217A: Global MASTER-Net observations report
- GRB 251217A: Fermi GBM Final Real-time Localization
- GRB 251215A: Swift/UVOT Upper LImits
- GRB 251215A: Fermi GBM Observation
- Fermi GRB 251216A: Global MASTER-Net observations report
- GRB 251202A/EP251202a: Koshka optical upper limit
- GRB 251214B: Mondy optical upper limit
- GRB 251215A: COLIBRÍ optical upper limit
- GRB 251216A: Fermi GBM Final Real-time Localization
- EP251214b: KAIT optical upper limit
- GRB 251215A: Swift-XRT observations
- Fermi GRB 251215A: Global MASTER-Net observations report
- EP251214a: Optical upper limit with Kinder observations
- GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
- GRB 251215A: Glowbug gamma-ray detection
- GRB 251214B: UAFO optical upper limit
- GRB 251214B: VLT/X-shooter observations
- GRB 251213A: GRID-10B observation
- GRB 251214B: Swift-BAT refined analysis
- GRB 251202A: radio detection with the VLA
- EP251214b: Global MASTER-Net observations report
- EP251214b : Einstein Probe detection of a fast X-ray transient
- EP251214b : Einstein Probe detection of a fast X-ray transient
- GRB 251214B: AbAO optical observations
- GRB 251214B: LCO detection of the optical counterpart
- GRB 251209A: GECAM-B observation of a long burst
- GRB 251214D: GECAM-B observation of a long burst
- GRB 251214B: Fermi GBM Observation
- GRB 251209A: Insight-HXMT/HE detection
- GRB 251215A: Swift ToO observations
- EP251214b (EP trigger 01709250023): LCO optical limits
- GRID detection of GRB 251213A
- GRB 251203B: AbAO optical observations
- GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst
- GRB 251214B: GECAM-B observation of a long burst
- GRB 251214B: Swift-XRT refined Analysis
- GRB 251213A: SVOM/GRM observation
- EP251214a: KAIT optical upper limit
- GRB 251214D: AstroSat CZTI detection of a long burst
- GRB 251213A: AstroSat CZTI detection
- GRB 251214A: AstroSat CZTI detection
- GRB 251213A: GECAM-B detection
- GRB 251214B: Swift/UVOT Detection
- GRB 251215A: Fermi GBM Final Real-time Localization
- GRB 251214B: COLIBRÍ observations of the afterglow
- EP251214a: EP-FXT non-detection and upper limit
- GRB 251214A: GECAM-B observation of a likely long burst
- GRB 251214B: 1.3m DFOT optical detection
- EP251214a: Global MASTER-Net observations report
- GRB 251214B: Enhanced Swift-XRT position
- GRB 251214B: Xinglong-2.16m optical observation
- GRB 251214C: Fermi GBM Final Localization
- GRB 251214B : MASTER optical afterglow detection
- Fermi trigger No 787396657: Global MASTER-Net observations report
- GRB 251214B: SVOM/C-GFT optical observations
- EP251214a: COLIBRÍ optical upper limit