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').
- GRB 230228A: OSN optical upper limit
- Fermi trigger No 699311646: Global MASTER-Net observations report
- GRB 230301A: Fermi GBM Final Real-time Localization
- GRB 230228A: Swift-XRT refined Analysis
- GRB 230228A: Mondy optical upper limit
- GRB 230228A: Enhanced Swift-XRT position
- GRB 230228A: Nanshan/NEXT optical upper limit
- GRB 230228A: Miryang Arirang Astronomical Observatory (MAAO) 0.7-m telescope optical upper limit
- GRB 230228A: Prompt enhanced Swift-XRT position
- GRB 230228A: Swift detection of a possibly short burst
- Fermi GRB 230227A: Global MASTER-Net observations report
- GRB 230227A: Fermi GBM Final Real-time Localization
- Fermi trigger No 699029364: Global MASTER-Net observations report
- GRB 230217A: VLT/FORS2 optical observations and candidate counterpart
- GRB 230216A Mondy Observations
- GRB 230205A: VLA radio afterglow confirmation
- IceCube-230220A: Upper limits from a search for additional neutrino events in IceCube
- GRB 230217A: Swift/UVOT Upper Limits
- GRB 230216A: Swift/UVOT Upper Limits
- GRB 230217A: Continued Gemini Observations
- GRB 230220A: Correction to GCN 33352
- GRB 230222A: Fermi GBM Final Real-time Localization
- GRB 230217A: Swift-XRT afterglow detection
- Fermi-LAT gamma-ray observations of IceCube-230220A
- GRB 230217A: Swift-BAT refined analysis
- Fermi GRB 230220B: Global MASTER-Net observations report
- GRB 230217A: AstroSat CZTI detection
- GRB 230217A: Gemini South optical upper limits
- GRB 230216B: CALET Gamma-Ray Burst Monitor detection
- GRB 230217A: 6 GHz VLA observations
- GRB 230220B: Fermi GBM Final Real-time Localization
- GRB 230217A: Gemini-South Optical Observation
- IceCube-230217A: Upper limits from a search for additional neutrino events in IceCube
- IceCube-230220A - IceCube observation of a high-energy neutrino candidate
- GRB 230217A: Fermi GBM observation
- GRB 230220A: MAXI/GSC detection
- IceCube-230217A: BOOTES-4/MET Optical Observations
- Fermi-LAT gamma-ray observations of IceCube-230217A
- Konus-Wind detection of GRB 230217A
- GRB 230217A: Swift-XRT observations
- Fermi trigger No 698427992: Global MASTER-Net observations report
- IceCube Alert 230217.87: Global MASTER-Net observations report
- GRB 230218A is not a GRB
- GRB 230218A: Fermi GBM Final Real-time Localization
- GRB 230217A: AGILE/MCAL detection
- GRB 230207B: CALET Gamma-Ray Burst Monitor detection
- GRB 230216B: AstroSat CZTI detection
- GRB 230216A: SVOM/C-GFT optical upper limit
- GRB 230217A: Swift detection of a short burst
- GRB 230217A: Fermi GBM Final Real-time Localization
- IceCube-230217A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 230216A: Swift-BAT refined analysis
- GRB 230216A: Swift-XRT refined Analysis
- GRB 230205A: Lowell Discovery Telescope Observations
- GRB 230204B: Lowell Discovery Telescope Observations
- Swift GRB 230216A: Global MASTER-Net observations report
- GRB 230216A: Enhanced Swift-XRT position
- GRB 230216A: AKO Upper Limit
- GRB 230216A: Zadko observatory - Gingin optical observations
- GRB 230216A: Swift detection of a burst
- Fermi GRB 230215A: Global MASTER-Net observations report
- GRB 230215A: Fermi GBM Final Real-time Localization
- GRB 230209B: AGILE detection
- GRB 230209B: Fermi GBM Observation
- IPN triangulation of GRB 230209B
- GRB 230204B: CALET Gamma-Ray Burst Monitor detection
- GRB 230204B: ATCA radio detection
- Outburst from LS V +44 17 / RX J0440.9+4431: Transient detection by GRBAlpha
- Fermi trigger No 697926015: Global MASTER-Net observations report
- Fermi trigger No 697904388: Global MASTER-Net observations report
- 230211A is not a GRB
- GRB 230211A: Fermi GBM Final Real-time Localization
- GRB 230209B: Swift/BAT-GUANO detection outside the coded FOV
- Fermi trigger No 697678542: Global MASTER-Net observations report
- Swift Trigger 1153670 is probably not a GRB
- GRB 230210A: Fermi GBM Final Real-time Localization
- Fermi GRB 230209B: Global MASTER-Net observations report
- GRB 230209B: Fermi GBM Final Real-time Localization
- GRB 230205A: 6 GHz VLA observations
- GRB 230209A is not a GRB
- GRB 230205A: SUBARU HSC pre-imaging for host galaxy search
- GRB 230209A: Fermi GBM Final Real-time Localization
- GRB 221009A: Continued Swift Observations
- Fermi Gamma-ray Burst Monitor trigger 230208382/697540213 is not a GRB
- GRB 230207B: Detection by GRBAlpha
- GRB 230205A: possible host galaxy detection with the Schmidt - Asiago telescope
- GRB 230204B: MASTER early OT detection
- GRB 230208A: Fermi GBM Final Real-time Localization
- Fermi Gamma-ray Burst Monitor triggers 230206723/697396830 and 230206797/697403223 are not GRBs
- GRB 230207B: Swift/BAT-GUANO detection outside the coded FOV
- ZTF23aabmzlp/AT2023azs: Neil Gehrels Swift Observatory X-ray observations
- GRB 230207B: AGILE detection of a burst
- Fermi GRB 230207A: Global MASTER-Net observations report
- GRB 230207A: Fermi GBM Final Real-time Localization
- GRB 230204B: LCOGT Optical Upper Limits
- GRB 230204B: Swift/UVOT Upper Limits
- Fermi trigger No 697403223: Global MASTER-Net observations report
- Fermi trigger No 697396830: Global MASTER-Net observations report
- GRB 230205A: Swift/UVOT Upper Limits
- GRB 230204B: Fermi GBM detection