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 231230A: GOTO optical upper limits
- GRB 231230A: Enhanced Swift-XRT position
- GRB 231230A: Swift/UVOT Upper Limits
- GRB 231230A: NOT optical upper limits
- Fermi trigger No 725592555: Global MASTER-Net observations report
- GRB 231230A: Prompt enhanced Swift-XRT position
- GRB 231230A: Swift detection of a burst
- Swift GRB231230.06: Global MASTER-Net observations report
- GRB 231230A: Fermi GBM Final Real-time Localization
- GRB 231210B: BOOTES-7 optical upper limit
- Swift Triggers 1205103, 1205104, 1205107 and 1205110 are not astrophysical events
- LIGO/Virgo/KAGRA S231224e: Upper limits from Swift/BAT-GUANO
- IPN triangulation of GRB 231224A (short)
- LIGO/Virgo/KAGRA S231226av: Updated Sky localization
- LIGO/Virgo/KAGRA S231226av: Identification of a GW compact binary merger candidate
- Fermi trigger No 725143760: Global MASTER-Net observations report
- GRB 231224A: Fermi GBM Final Real-time Localization
- GRB 231222B: GRBAlpha detection
- LIGO/Virgo/KAGRA S231224e: Updated Sky localization and Source Classification
- LIGO/Virgo/KAGRA S231224e: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S231223j: Updated Sky localization
- GRB 231222B: Swift-XRT afterglow detection
- LIGO/Virgo/KAGRA S231223j: Identification of a GW compact binary merger candidate
- Fermi trigger No 724921799: Global MASTER-Net observations report
- GRB 231222B: Fermi GBM Detection
- LAT GRB231222.31: Global MASTER-Net observations report
- GRB 231222B: Fermi-LAT detection
- GRB 231222A: Tiled Swift observations
- IceCube-231211A: GRANDMA observations of PKS2047+098
- GRID detection of GRB 231215A
- GRB 231222A: Fermi GBM Final Real-time Localization
- GRB 231220A: Swift-XRT follow-up observations
- GRB 231220A: Swift ToO observations
- GRB 231220A: Swift/BAT-GUANO arcminute localization of a long burst
- Fermi trigger No 724781422: Global MASTER-Net observations report
- GRB 231220A: Fermi GBM Final Real-time Localization
- GRB 231210B: new optical transient detected with the Greenhill Observatory University of Tasmania within the BAT-Swift enhanced position
- Fermi trigger No 724698747: Global MASTER-Net observations report
- GRB 231219A: Fermi GBM Final Real-time Localization
- GRID detection of GRB 231205B
- GRID detection of GRB 231205A
- GRB 231216A: GAD Observatory, La Spezia, Italy upper limit
- GRB 231214B: Fermi GBM observation
- GRB 231216A: optical upper limits from the INAF Asiago Observatory
- GRB 231216A: 10.4 m GTC optical upper limit
- GRB 231215A: AMI-LA radio detection
- GRB 231216A: Nanshan/HMT optical upper limit
- GRB 231216A: LCOGT Optical Upper Limits
- GRB 231216A: Osservatorio Astronomico Nastro Verde upper limit
- GRB 231216A: Swift-XRT refined analysis correction
- GRB 231215A: Osservatorio Astronomico Nastro Verde upper limit
- GRB 231216A: Swift-XRT refined Analysis
- GRB 231216A: AST3-3 YaoAn Optical Upper Limit
- GRB 231216A: REM NIR upper limits
- GRB 231216A: Swift/UVOT Upper Limits
- GRB 231216A: Swift-BAT refined analysis
- GRB 231215A: Swift-BAT refined analysis
- GRB 231214A: Swift-BAT refined analysis
- GRB 231216A: R-band observations from T120 at Observatoire de Haute-Provence
- GRB 231216A: GIT optical upper limit
- GRB 231216A: NOT optical upper limits
- GRB 231216A: BOOTES-2/TELMA optical upper limit
- GRB 231215A: GRBAlpha detection
- Swift GRB231216.77: Global MASTER-Net observations report
- GRB 231216A: Swift detection of a burst
- Konus-Wind detection of GRB 231215A
- GRB 231215A: optical afterglow detection from the INAF Asiago Observatory
- GRB 231215A: NOT optical observations
- GRB 231214A: Swift/UVOT Upper Limits
- GRB 231215A: Redshift from OSIRIS+ / GTC
- GRB 231205B: VZLUSAT-2 detection
- GRB 231204A: VZLUSAT-2 detection
- GRB 231215A: GAD Observatory, La Spezia, Italy upper limit;
- GRB 231215A: Fermi GBM observation
- GRB 231215A: CALET Gamma-Ray Burst Monitor detection
- GRB 231215A : OHP/T193 optical afterglow detection
- GRB 231215A: Swift/UVOT Detection
- LIGO/Virgo/KAGRA S231215i: 3 counterpart neutrino candidate events from an IceCube neutrino search
- GRB 231215A: Swift-XRT refined Analysis
- GRB 231215A: BOOTES-4/MET optical detection
- GRB 231215A: AKO Optical Upper Limit
- GRB 231215A: AGILE detection
- GRB 231214A: Fermi GBM observation
- Konus-Wind detection of GRB 231210B
- ATCA observations of GRB 231210B
- GRB 231215A: Enhanced Swift-XRT position
- Fermi trigger No 724326442: Global MASTER-Net observations report
- GRB 231214A: REM optical/NIR upper limits
- GRB 231215A: GROWTH-India optical follow-up
- GRB 231215A : Nanshan/HMT optical observations
- GRB 231215A: AstroSat CZTI detection
- GRB 231215A : MITSuME Akeno optical afterglow candidate detection
- GRB 231214A: Swift-XRT refined Analysis
- GRB 231215A: Mondy optical bright afterglow detection
- GRB 231214A: AstroSat CZTI detection
- GRB 231215C: MASTER OT detection
- Swift GRB231215.41: Global MASTER-Net observations report
- GRB 231215A: Swift-XRT observations
- GRB 231215B: Fermi GBM Final Real-time Localization
- GRB 231215A: Swift detection of a burst