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').
- Fermi Gamma-ray Burst Monitor triggers due to recent activity of RX J0440.9+4431 (LS V +44 17)
- GRB 230205A: LCOGT Optical Upper Limits
- GRB 230204B: Swift-XRT afterglow detection
- GRB 230204B: 3.6m DOT optical observation
- GRB 230205A: SVOM/C-GFT optical upper limit
- GRB 230205A: OHP/T193 optical observations
- GRB 230204B: VLT/X-shooter redshift
- GRB 230205A: Swift-BAT refined analysis (T90 = 2.3 s)
- GRB 230204A: Swift-BAT refined analysis
- GRB 230204B: ATLAS detection of the optical afterglow and a projected location in a nearby galaxy group
- GRB 230205A: Swift-XRT refined Analysis
- GRB 230204B: Swift ToO observations
- GRB 230205A: Enhanced Swift-XRT position
- GRB 230205A: BOOTES-5/JGT early optical upper limit
- GRB 230204B: Detection by GRBAlpha
- GRB 230204B: AGILE detection
- GRB 230205A: Swift detection of a burst
- IceCube-230201A: BOOTES-4/MET Optical Upper Limits
- GRB 230204B: GIT discovery of the likely optical afterglow
- GRB 230204B: AstroSat CZTI detection
- GRB 230204B: Swift/BAT-GUANO detection outside the coded FOV
- GRB 230204A: Swift/UVOT Upper Limits
- GRB 230204B: MAXI/GSC detection
- GRB 230204A: Swift-XRT refined Analysis
- GRB 230204A/Swift J1552.8-5055: LCOGT Optical Counterpart Candidate
- Fermi trigger No 697208885: Global MASTER-Net observations report
- GRB 230204A: Enhanced Swift-XRT position
- GRB 230204A: Swift detection of a possible burst (or possible transient Swift J1552.8-5055)
- GRB 230201B: TURBO Optical Upper Limits
- Fermi Gamma-ray Burst Monitor trigger 230203275 / 697098930 is not a GRB
- Fermi trigger No 697098930: Global MASTER-Net observations report
- IceCube-230201A: Upper limits from a search for additional neutrino events in IceCube
- ZTF23aabmzlp/AT2023azs: Lulin 1m LOT optical observations
- GRB 221216A: Swift-BAT refined analysis
- ZTF23aabmzlp/AT2023azs: VLA radio detection
- ZTF23aaarlti/AT2023avj: AMI-LA radio detection
- ZTF23aabmzlp/AT2023azs: AMI-LA radio upper limit
- IceCube Alert 230201.26: Global MASTER-Net observations report
- Fermi GRB 230201B: Global MASTER-Net observations report
- Fermi-LAT gamma-ray observations of IceCube-230201A
- GRB 230201B: Fermi GBM Final Real-time Localization
- GRB 230126A: Detection by VZLUSAT-2
- Fermi GRB 230201A: Global MASTER-Net observations report
- IceCube-230201A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 221009A: radio afterglow detection with the EVN
- GRB 230201A: Fermi GBM Final Real-time Localization
- ZTF23aabmzlp/AT2023azs: LCOGT Optical Detection
- ZTF23aaarlti/AT2023avj: Assy continued optical observations
- ZTF23aabmzlp/AT2023azs: Mondy and AbAO optical observations
- AT2023avj: X-ray Detection with Swift/XRT
- ZTF23aabmzlp/AT2023azs: 1.3m DFOT optical observations
- GRB 230129A: AstroSat CZTI detection
- GRB 230128A: AstroSat CZTI detection
- GRB 230130A: Fermi GBM Final Real-time Localization
- ZTF23aaarlti/AT2023avj: VLA radio detection
- GRB 230129A: Fermi GBM Final Real-time Localization
- GRB 230128A: Fermi GBM Final Real-time Localization
- ZTF23aabmzlp/AT2023azs: GIT confirmation of the likely afterglow
- ZTF23aabmzlp/AT2023azs: Zwicky Transient Facility discovery of a fast optical transient
- IceCube-230122A: BOOTES-2/TELMA Optical Upper Limit
- AT2023avj ZTF Candidate: Assy optical observations
- ZTF and LT Observations of AT2023avj, a Candidate Optical Afterglow
- GRB 230126A: Fermi GBM Final Real-time Localization
- Swift-XRT observations of NuEm-230125A
- Trigger 1150965: Swift detection of LS V +44 17
- GRB 230124A: Fermi GBM Observation
- AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230125A
- GRB 230124A: Swift/BAT-GUANO detection outside the coded FOV
- IceCube-230122A: Upper limits from a search for additional neutrino events in IceCube
- GRB 230114B: Detection by VZLUSAT-2
- GRB 230123A: LCOGT Optical Upper Limits
- Fermi GRB 230124A: Global MASTER-Net observations report
- GRB 230124A: Fermi GBM Final Real-time Localization
- GRB 230123A: Swift-BAT refined analysis
- GRB 230122A: Swift/BAT-GUANO detection
- Fermi-LAT gamma-ray observations of IceCube-230122A
- GRB 230123A: Swift/UVOT Upper Limits
- GRB 230123A: Swift-XRT refined Analysis
- GRB 230123A: Enhanced Swift-XRT position
- GRB 230123A: Zadko observatory - Gingin optical observations
- GRB 230116C: Swift-XRT observations
- GRB 230123A: Swift detection of a burst
- IceCube Alert 230122.16: Global MASTER-Net observations report
- IceCube-230122A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 230116B: Fermi GBM observation
- Trigger 1150107: Swift detection of LS V +44 17
- GRB 230120A: AstroSat CZTI detection
- IPN triangulation of GRB 230116B (short)
- GRB 230119A: CALET Gamma-Ray Burst Monitor detection
- GRB 230116D: 3.6m DOT optical upper limit
- GRB 230119A: Fermi GBM Final Real-time Localization
- Fermi GRB 230118A: Global MASTER-Net observations report
- GRB 230118A: Fermi GBM Final Real-time Localization
- GRB 230116D: Swift-BAT refined analysis
- GRB 230116C: Swift-BAT refined analysis
- GRB 230116D: SAO RAS further observations
- GRB 230116D: SAO RAS photometry
- GRB 230116D: KGO RC-25 optical observations
- GRB 230116D: Sintez-Newton/CrAO optical observations
- GRB 230116D: LCOGT Optical Upper Limit