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 210226A: Swift-BAT refined analysis
- GRB 210226A: Fermi GBM detection
- GRB 210217A: Mondy optical observations
- GRB 210226A: KAIT Optical Upper Limit
- GRB 210226A: Swift-XRT refined Analysis
- Swift GRB 210226A: Global MASTER-Net observations report
- GRB 210218A: Swift-XRT confirmation of afterglow
- GRB 210226A: Burke-Gaffney Observatory optical upper limit
- GRB 210226A: Enhanced Swift-XRT position
- GRB 210226A: Ondrejov BART/SBT optical limit
- GRB 210222B: 1.3m DFOT Optical upper limit
- GRB 210226A: Swift detection of a burst
- GRB 210222B: REM observations of the optical/NIR afterglow
- Fermi trigger No 635922820: Global MASTER-Net observations report
- GRB 210222B: MITSuME Akeno optical upper limits
- Konus-Wind detection of GRB 210222A
- GRB 210222B: Zeiss-1000 of Koshka observatory, optical observations
- GRB 210222B: VIRT optical detection
- GRB 210222B: Swift-BAT refined analysis
- GRB 210222B: Swift-XRT refined Analysis
- GRB 210222B: Swift/UVOT Detection
- GRB 210222B: KAIT Optical Upper Limit
- GRB 210222B: FRAM-ORM afterglow detection
- GRB 210218A: Swift/UVOT observations
- GRB 210217A: Swift/UVOT Detection
- GRB 210222B: MASTER OT observation
- GRB 210222A: CALET Gamma-Ray Burst Monitor detection
- GRB 210222B: Redshift from FORS2/VLT
- GRB 210222B: NEXT early optical afterglow observations
- GRB 210222B: GOTO confirmation of afterglow detection (correction to GCN29548)
- GRB 210222B: Liverpool Telescope optical detection
- GRB 210222B: GOTO confirmation of afterglow detection
- GRB210222B: LCO Optical Afterglow Detection
- GRB210222B: BOOTES-1 optical afterglow detection
- GRB 210222B: Swift detection of a burst with an optical counterpart
- Swift GRB210222.94: Global MASTER-Net observations report
- GRB 210222A: MAXI/GSC detection
- GRB 210218A: Swift-XRT observations
- uGMRT radio detection of GRB 210204A
- GRB 210212A: Lowell Discovery Telescope observations
- GRB 210217A: 1.3m DFOT optical detection
- GRB 210217A: Swift-XRT refined Analysis
- GRB 210218A: Swift-BAT refined analysis
- Fermi GBM Sub-Threshold Detection of GRB 210217A
- GRB 210217A: Liverpool Telescope First Hour Observations
- GRB 210217A: Swift-BAT refined analysis
- GRB 210217A: KAIT Optical Observations
- GRB 210218A: MITSuME Akeno optical upper limits
- GRB 210218A： GWAC-F60A optical upper limit
- GRB 210218A: NEXT optical upper limit
- GRB 210218A: Swift detection of a burst
- Subject: ZTF21aakruew/AT2021cwd: GROND observations
- GRB 210212A: REM early-time optical/NIR upper limits
- GRB 210205A: observations with the 3.6m DOT, a potential dark burst?
- GRB 210217A: Enhanced Swift-XRT position
- Fermi/GBM observation of a burst from SGR 1830-0645
- GRB 210217A: NEXT early optical afterglow observations
- GRB 210212A: Mondy optical observations
- GRB 210217A: Swift detection of a burst with an optical counterpart
- GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Assy and Mondy optical observations
- IceCube-210210A: Two Additional Optical Candidate Counterparts Found by DECam
- GRB 210208A: 1.3m DFOT Optical upper limit
- GRB 210210A: Konus-Wind detection and joint Konus-Wind + Swift-BAT spectral analysis
- Swift Trigger 1033144: Detection of SGR 1830-0645
- GRB 210211A: ePESSTO+ NTT optical observations
- Konus-Wind detection of GRB 210212B / ZTF21aakruew
- GRB 210212B: Swift ToO observations
- GRB 210212B (TF21aakruew/AT2021cwd): Assy optical observations
- IPN triangulation of GRB 210212B (consistent with ZTF21aakruew/AT2021cwd)
- GRB 210212A: 1.3m DFOT Optical upper limit
- GRB 210213B: Insight-HXMT/HE detection
- ZTF21aakruew/AT2021cwd: ZTF and LT discovery of a hostless, red, and rapidly fading optical transient
- GRB 210212A: Gemini South optical observations
- IceCube alert 134994_1103075 retraction
- Fermi GRB 210213A: Global MASTER-Net observations report
- IceCube Alert 210213.78: Global MASTER-Net observations report
- GRB 210213A: Fermi GBM Final Real-time Localization
- GRB 210210A: CAHA 2nd epoch and jet break confirmation
- IceCube-210210A: Four Candidate Optical Counterparts from DECam Observations
- Swift Trigger 1032350: Detection of SGR 1830-0645
- GRB 210204A (ZTF21aagwbjr/AT2021buv): continued CrAO and AbAO optical observations
- GRB 210212A: Possible host galaxy counterpart with the NOT
- Swift GRB 210212A: Global MASTER-Net observations report
- GRB 210212A: MITSuME Akeno optical upper limits
- GRB 210212A: Swift-XRT refined Analysis
- GRB 210212A: BOOTES-4/MET optical upper limit
- IceCube-210210A: Upper limits from a search for additional neutrino events in IceCube
- GRB 210212A: Swift/UVOT Upper Limits
- GRB 210212A: Swift-BAT refined analysis
- GRB 210204A: observations with the 3.6m Devasthal Optical Telescope and possible jet break
- GRB 210212A: Enhanced Swift-XRT position
- GRB 210210A : 1.3m DFOT optical observations
- GRB 210212A: Swift detection of a burst
- GRB 210207B: GECAM detection
- GRB 210211A: Swift/UVOT Detection
- GRB 210211A: Swift-XRT refined Analysis
- GRB 210211A: Swift-BAT refined analysis
- GRB 210211A: Fermi GBM observation
- GRB 210210A as a BdHN II
- Swift-XRT observations of IceCube-210210A