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"- EP260213a: COLIBRÍ optical upper limits
- GRB 260212A: GECAM-B observation
- EP260213a: Optical upper limits with Kinder observations
- EP260213a: SVOM/VT optical upper limit
- EP260213a: Mondy R-band optical upper limit
- EP260213a: NUTTelA-TAO Early Optical Limits
- EP260213a: SVOM/C-GFT upper limit
- EP260213a: refined analysis of the EP-FXT observation
- EP260213a: Einstein Probe detection of a fast X-ray transient
- EP/WXT 01709258378: NOT optical upper limits
- GRB 260212A: SVOM/GRM observation of a long burst
- GRB 260213B: Fermi GBM Final Localization
- GRB 260213B: BALROG localization (Fermi Trigger 792697214 / GRB 260213736)
- GRB 260211A - SVOM/ECLAIRs refined analysis
- GRB 260204A: SVOM/ECLAIRs refined analysis
- GRB 260213A: Fermi GBM Final Localization
- GRB 260211A: EP-FXT follow-up observation
- GRB 260211A: SVOM/VT optical observation
- GRB 260212A: Glowbug gamma-ray detection
- GRB 260211A: GOTO optical upper limit
- Fermi GRB 260212A: Global MASTER-Net observations report
- GRB 260212A: Fermi GBM Final Real-time Localization
- GRB 260211A: LAST optical upper limit
- GRB 260210A: SVOM/GRM observation
- Fermi GBM Sub-Threshold Detection of GRB 260211A
- Konus-Wind detection of GRB 260207B
- GRB 260128B: SVOM/ECLAIRs refined analysis
- GRID detection of GRB 260207B
- GRB 260211A: LCO optical upper limits
- GRB260131A/B: 3.6m DOT Optical Observations
- GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
- Fermi trigger No 792537871: Global MASTER-Net observations report
- GRB 260211A: SVOM detection of a burst
- Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
- Konus-Wind detection of GRB 260209B
- GRB 260208A: Swift UVOT detection
- Konus-Wind detection of GRB 260127B
- EP260209a: COLIBRÍ optical upper limit
- Fermi GRB 260210C: Global MASTER-Net observations report
- EP260209a: LCO optical upper limits
- EP260210a: Global MASTER-Net observations report
- EP260210a: refined analysis of the EP-FXT observation
- EP260209a: Global MASTER-Net observations report
- GRB 260208A: LCO detection of the optical counterpart
- EP260209a: Einstein Probe detection of a fast X-ray transient
- EP260210a: Optical upper limits with Kinder observations
- IPN triangulation of GRB 260207B (short/hard with EE)
- GRB 260210C: Fermi GBM Final Real-time Localization
- GRB 260210A: Glowbug gamma-ray detection
- GRB 260210B: Fermi GBM Final Real-time Localization
- EP260210a: SVOM/VT optical upper limit
- GRB 260210A: AstroSat CZTI detection
- GRB 260208C: AstroSat CZTI detection
- EP260210a: COLIBRÍ optical upper limit
- EP260210a: SVOM/C-GFT upper limit
- GRB 260208B: refined analysis of the EP-FXT observation
- EP260210a: Einstein Probe detection of an X-ray transient
- GRB 260207B: AstroSat CZTI detection
- GRB 260208C: SVOM/GRM observation
- GRB 260204A: Swift-XRT afterglow detection
- GRB 260208B: AstroSat CZTI detection of a bright long burst
- GRB260208A: Liverpool Telescope optical follow-up observations
- GRB 260208A: Glowbug gamma-ray detection
- GRB 260208A: NuSTAR detection of prompt emission
- GRB 260208A: Fermi GBM Observation
- Fermi GRB 260209A: Global MASTER-Net observations report
- GRB 260208B: Swift-XRT observations
- GRB 260131A/B: continued Mondy optical observations
- GRB 260204A: Swift/UVOT Upper Limits
- GRB 260208B: COLIBRÍ optical observations
- GRB 260208A: Mondy optical observations (duplicate submission)
- GRB 260208A: Mondy optical observations
- GRB 260208A: 1.3m DFOT optical detection
- GRB 260208A: COLIBRÍ optical observations
- GRB 260208B: EP-FXT observation
- GRB 260208A: NOT spectroscopic redshift z = 2.36
- GRB 260208A: Liverpool Telescope optical detection
- Fermi GRB 260208C: Global MASTER-Net observations report
- GRB 260208B: SVOM/VT optical candidate
- GRB 260208A: GECAM-B observation of a bright burst
- GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
- GRB 260209A: Fermi GBM Final Real-time Localization
- GRB 260208A: SVOM/VT optical observation
- Fermi GRB 260208D: Global MASTER-Net observations report
- GRB 260208D: Fermi GBM Final Real-time Localization
- GRB 260208A: Swift-XRT observations
- GRB 260208B: Swift ToO observations
- GRB 260208B: SVOM/GRM observation of a bright burst
- GRB 260208B: Fermi GBM Detection
- LAT GRB 260208B: Global MASTER-Net observations report
- GRB 260208B: Fermi-LAT detection
- GRB 260208C: Fermi GBM Final Real-time Localization
- GRB 260208A: Fermi-LAT detection
- GRB 260207B: GECAM-B observation
- GRB 260208A: Swift ToO observations
- GRB 260208A: Fermi GBM Classification Correction
- GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
- GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
- GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
- GRB 260208B: Fermi GBM Final Real-time Localization