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 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
- Swift GRB 251214B: Global MASTER-Net observations report
- EP251214.305: COLIBRÍ optical upper limit
- GRB 251214B: Swift detection of a burst with an optical counterpart
- GRB 251214B: Fermi GBM Final Real-time Localization
- EP251214a: EP-WXT detection of an X-ray transient possibly associated with GRB 251214A
- Fermi GRB 251214A: Global MASTER-Net observations report
- GRB 251214A: Fermi GBM Final Real-time Localization
- EP251212a: Global MASTER-Net observations report
- EP251212a: KAIT optical upper limit
- EP251212a / GRB 251212A: AstroSat CZTI detection
- EP251212a: EP-FXT follow-up observation
- GRB 251211B: AstroSat CZTI detection
- IceCube-251210A: No Candidate Transients from the Zwicky Transient Facility
- GRB 251209A: NuSTAR detection of prompt emission
- EP251212a : COLIBRÍ optical upper limit
- EP251212a: Einstein Probe detection of an X-ray transient
- Fermi-LAT Gamma-ray Observations of IceCube-251210A
- IceCube-251210A: Upper limits from a search for additional neutrino events in IceCube
- Fermi GRB 251211B: Global MASTER-Net observations report
- GRB 251211B: Fermi GBM Final Real-time Localization
- IceCube-251210A: DDOTI Optical Upper Limit
- SVOM GRB251211.12: Global MASTER-Net observations report
- GRB 251211A: Fermi GBM Final Real-time Localization
- GRB 251209A: Fermi GBM observation
- GRB 251205A: 1.3m DFOT optical upper limit
- GRB 251209A: AstroSat CZTI detection
- IceCube Alert 251210.46: Global MASTER-Net observations report
- IceCube-251210A - IceCube observation of a high-energy neutrino candidate track-like event
- EP251124a: Mondy optical upper limit
- GRB 251129A/EP251129a: AbAO and Mondy optical observations
- EP251130a: Mondy and AbAO optical observations
- GRB 251208A: AstroSat CZTI detection
- Fermi GBM Sub-Threshold Detection of GRB 251205A
- GRB 251208A: Glowbug gamma-ray detection
- GRB 251208B: COLIBRÍ optical upper limits
- EP251118a / GRB 251118C: VLT/MUSE redshift confirmation
- GRB 251208C: GECAM-B observation of a short burst
- GRB 251208A: GECAM-B observation of a short burst
- Fermi GRB 251209A: Global MASTER-Net observations report
- Fermi GRB 251208C: Global MASTER-Net observations report
- GRB 251206A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 251208B: Swift-XRT afterglow detection
- GRB 251208D: LAST optical upper limit
- GRB 251209A: Fermi GBM Final Real-time Localization
- GRB 251208D: LCO analysis of the XRT sources
- GRB 251208B: Fermi GBM Observation
- GRB 251208B: GROWTH-India Telescope optical upper limits
- GRB 251205A: J-band detection with WINTER
- GRB 251208D: Swift-XRT observations
- GRB 251208A: SVOM/GRM observation of a short burst
- GRB 251208C: SVOM/GRM observation of a short burst
- GRB 251129A: e-MERLIN C-band observations
- LAT GRB251208.43: Global MASTER-Net observations report
- GRB 251205A: Liverpool Telescope further optical follow-up observations
- GRB 251208D: LCO optical upper limits
- SVOM GRB251208D: Global MASTER-Net observations report
- GRB 251208B: Swift ToO observations
- GRB 251208B: Fermi-LAT detection
- GRB 251208B: Swift/BAT-GUANO arcminute localization of a burst