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 161228C: POLAR observation
- GRS 1716-249/GRO J1719-24/V2293 Oph, Swift-BAT refined analysis
- GRB 170101A: POLAR observation
- GRB 161229A: POLAR observation
- GRB 170101A: Swift-BAT refined analysis
- Trigger 729410: Swift detection of V2293 Oph
- GRB 170101B: Astrosat CZTI detection
- GRB 170101B: Fermi GBM detection
- GRB 170101A: Swift detection of a burst
- GRB 161228B: POLAR Observation
- GRB 161228A: POLAR Observation
- GRB161219B - Anticipated hyperluminal evidence
- GRB 161214B: MASTER-Kislovodsk early optical observations
- GMRT radio detection of GRB 161219B
- GRB 161214A: MASTER-IAC early optical observations
- GRB 161219B: Spectroscopic detection of the associated SN with OSIRIS/GTC
- Fermi GBM trigger 504490076/161227005 is not a GRB
- GRB 161224A: TSHAO optical observations
- GRB 161224A: Swift/UVOT Upper limits
- GRB 161224A: Swift-XRT refined Analysis
- GRB 161224A: Swift-BAT refined analysis
- Trigger 728094, Swift-BAT refined analysis
- Swift Trigger 728268: a possible GRB
- Fermi GBM trigger 504233075/161224301 is not a GRB
- Swift Trigger 728094: a possible GRB
- GRB 161219B: UKIRT near-IR afterglow detection
- GRB 161219B: POLAR Observation
- GRB161219.78 MASTER-Net OT detection
- Fermi GBM trigger 504061556/161222046 is not a GRB
- GRB 161219B: Rapid ALMA Observations & Detection
- Correction to GCN 20323 "Konus-Wind observation of GRB 161219B"
- Fermi GBM trigger 504043585/161221838 is not a GRB
- GRB 161220A: Swift-BAT refined analysis
- GRB 161218B: Astrosat CZTI detection
- Konus-Wind observation of GRB 161219B
- GRB 161219B: SALT observations
- GRB 161219B: VLT/X-shooter redshift
- Fermi GBM trigger 503982114/161221126 is not a GRB
- GRB 161214B: optical spectroscopy of the foreground SDSS object
- GRB 161202A: 15 GHz upper limits from AMI
- GRB 161129A: 15 GHz upper limits from AMI
- GRB 161220A: Swift-XRT refined Analysis
- GRB 161220A: LCO-FTS observations
- GRB 161219B: MITSuME Akeno Optical Observation
- GRB 161219B: VLA Detection
- GRB 161220A: GROND Upper Limits
- GRB 161217C: POLAR observation
- GRB 161217B: POLAR Observation
- GRB 161219B: ISON/Terskol optical observations
- GRB 161219B: Swift-BAT refined analysis
- GRB 161220A: Swift/UVOT Upper Limits
- GRB 161219B: Swift/UVOT Detection
- GRB 161219B: Watcher optical observations
- Konus-Wind observation of GRB 161218B
- IPN Triangulation of GRB 161218B (long/very bright)
- GRB 161220A: Swift detection of a burst
- GRB 161212A: POLAR Detection
- GRB 161219B: LCO Sutherland observations
- GRB 161219B: GROND afterglow observations
- GRB 161219B: Swift-XRT refined Analysis
- GRB 161219B: Enhanced Swift-XRT position
- GRB 161219B: Swift detection of a burst with an optical afterglow
- GRB 161219A: a long GRB detected by INTEGRAL
- GRB 161218A: CALET Gamma-Ray Burst Monitor detection
- GRB 161218A: Swift-BAT refined analysis
- Konus-Wind observation of GRB 161218A
- Swift Trigger 727422 is not an astrophysical event.
- GRB 161218A: TAROT Calern observatory optical observations
- GRB 161217A: TAROT Calern observatory optical observations
- GRB 161218B: POLAR observation
- GRB 161218A: POLAR observation
- GRB 161218B: Fermi GBM detection
- GRB 161217A: MITSuME Okayama upper limits
- GRB 161217A: Swift-BAT refined analysis
- GRB 161218A: Swift detection of a burst
- GRB 161217A: Swift/UVOT Upper Limits
- GRB 161217A: Swift-XRT refined Analysis
- GRB 161214B: AbAO and ISON/Terskol optical observations
- GRB 161217A: Enhanced Swift-XRT position
- GRB 161207A: POLAR observation
- GRB 161217A: Swift detection of a burst
- GRB 161214B: Mondy optical observations
- GRB 161213A: POLAR Observation
- GRB 161207B: POLAR observation
- GRB 161205A: POLAR observation
- GRB 161210A: POLAR observation
- GRB 161214B: Swift-BAT refined analysis
- Fermi-LAT Gamma-ray Observations of IceCube-161210
- GRB 161214B: Swift/UVOT Afterglow Confirmation
- IceCube-161210: Kanata/HONIR near-infrared follow-up observation
- GRB 161214B: RATIR Optical and Near-Infrared Observations
- GRB 161214B: Swift-XRT refined Analysis
- GRB 161214B: Enhanced Swift-XRT position
- GRB 161214B: TAROT Calern observatory optical observations
- GRB 161214B: Chante-perdrix observatory optical observations
- GRB 161214B: Swift/UVOT Observations
- GRB 161214B: NOT optical observations, possible counterpart
- GRB 161214B: Prompt enhanced Swift-XRT position
- GRB 161214A: NOT observations of the afterglow
- GRB 161214B: Swift detection of a burst