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 210403A: Swift detection of a burst
- GRB 210402A: Montarrenti Observatory upper limit
- GRB 210328A: AstroSat CZTI detection
- GRB 210402A: NOT optical upper limits
- Konus-Wind detection of GRB 210401A
- GRB 210402A: Swift detection of a burst
- Fermi trigger No 639093861: Global MASTER-Net observations report
- Swift GRB210402.92: Global MASTER-Net observations report
- Fermi GRB 210401A: Global MASTER-Net observations report
- GRB 210401A: Fermi GBM Final Real-time Localization
- GRB 210330A: MASTER optical observation
- GRB 210328A: GECAM detection
- GRB 210330A: GECAM detection
- GRB 210324A: AstroSat CZTI detection
- GRB 210324C: AstroSat CZTI detection
- GRB 210328A: BALROG localization (Fermi Trigger / GRB 210328865)
- GRB 210328A: Fermi GBM Final Real-time Localization
- GRB 210326A: Insight-HXMT/HE detection
- GRB 210326A: Fermi GBM Final Localization
- Fermi trigger No 638414549: Global MASTER-Net observations report
- Konus-Wind detection of GRB 210324C
- IPN triangulation of GRB 210324C
- GRB 210323A: Insight-HXMT/HE detection
- GRB 210321A: OSN Upper Limit
- GRB 210323A: MASTER optical observation
- Fermi GRB 210324C: Global MASTER-Net observations report
- Fermi GRB 210324B: Global MASTER-Net observations report
- GRB 210323A: Swift-BAT refined analysis
- GRB 210323A: Gemini-North Optical Source Detection
- GRB 210324C: BALROG localization (Fermi Trigger 638308803 / GRB 210324833)
- GRB 210324C: Fermi GBM Final Real-time Localization
- Short GRB 210323A: GTC Observations
- GRB 210312B: OSN Afterglow Observations
- GRB 210324B: Fermi GBM Final Real-time Localization
- GRB 210323B: Swift ToO observations
- Konus-Wind detection of GRB 210323A (short)
- GRB 210323A: Swift/UVOT Upper Limits
- GRB 210323A: Classification and redshift estimation
- GRB 210323A: Kitab optical upper limit
- GRB 210323A: Fermi GBM detection
- GRB 210323A: Mondy optical observations, counterpart detection
- GRB 210324A: Fermi GBM Final Real-time Localization
- GRB 210318A: Swift/UVOT Upper Limits
- GRB 210323A: Swift-XRT refined Analysis
- GRB 210323A: Enhanced Swift-XRT position
- GRB 210323A: NOT optical afterglow candidate
- Swift GRB 210323A: Global MASTER-Net observations report
- GRB 210323B: Swift/BAT-GUANO detection and possible arcminute localization
- GRB 210323A: Nanshan/NEXT optical upper limit
- GRB 210323A: Swift detection of a short burst
- Fermi GBM trigger 637977270/210320996 is not a GRB
- GRB 210321A: Swift/UVOT Detection
- Konus-Wind detection of GRB 210321A
- GRB 210318B: Swift/UVOT Upper Limits
- GRB 210321A: DDOTI Position Correction
- IceCube Alert 210322.11: Global MASTER-Net observations report
- GRB 210321A: CrAO optical upper limit
- GRB 210321A: Swift-BAT refined analysis
- IceCube 135113_19489408.amon: Swift-XRT observations
- GRB 210321A: Mondy optical observations
- IceCube Astrotrack Bronze 135113_19489408.amon is likely background
- GRB 210321A: Xinglong GWAC-F60A optical observation
- GRB 210321A: Swift-XRT refined Analysis
- GRB 210321A: Redshift from OSIRIS/GTC
- GRB 210321A: NOT optical afterglow detection and redshift limit
- GRB 210321A: MASTER optical observation
- MAXI GRB210320.89: Global MASTER-Net observations report
- GRB 210321A: Enhanced Swift-XRT position
- GRB 210321A: DDOTI Afterglow Confirmation
- GRB 210321A: Swift/UVOT Detection
- GRB 210321A: Swift-XRT observations
- GRB 210321A: Swift detection of a burst
- GRB 210320A: MAXI/GSC detection
- GRB 210318B: MITSuME Okayama optical upper limits
- GRB 201216C: VIRT optical observations
- GRB 200524A: Redshift from Gemini-North
- GRB 210318A: Swift-BAT refined analysis
- GRB 210318A: Swift-XRT refined Analysis
- GRB 210318A: Enhanced Swift-XRT position
- Swift GRB210318.13: Global MASTER-Net observations report
- GRB 210318B: Fermi GBM detection
- Fermi trigger No 637729731: Global MASTER-Net observations report
- GRB 210318B: Swift-BAT refined analysis
- Swift GRB 210318A: Global MASTER-Net observations report
- Konus-Wind detection of GRB 210318B
- GRB210318B: Swift detection of a burst
- GRB 210318A: Swift detection of a burst
- Fermi GRB 210317A: Global MASTER-Net observations report
- GRB 210317A: GECAM detection
- GRB 210317A: Fermi GBM Final Real-time Localization
- Fermi trigger No 637521056: Global MASTER-Net observations report
- GRB 210306A: GIT optical follow-up
- GRB 210226A: GIT optical upper limit
- GRB 210312B: Redshift from OSIRIS/GTC
- GRB 210306A: HCT optical upper limit
- GRB 210312B: GTC photometry
- GRB 210312B: MASTER OT confirmation
- GRB210312B (Integral alert 9073): Candidate optical afterglow by Ondrejov D50
- GRB 210312B: A long GRB detected by INTEGRAL
- Integral GRB210312.87: Global MASTER-Net observations report