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 240225B: Liverpool Telescope optical afterglow observations
- GRB 240225B: NOT optical observations
- GRB 240218A: CMO SAI NIR upper limit
- Fermi GRB 240226A: Global MASTER-Net observations report
- Swift-BAT triggers 1217733 - 1217736 are not astrophysical events
- Swift-BAT triggers 1217729-1217732 are not astrophysical
- GRB 240227A: Fermi GBM Final Real-time Localization
- Fermi Gamma-ray Burst Monitor trigger 730618809/240226236 is not a GRB
- GRB 240225B: Nanshan/HMT optical afterglow detection
- GRB 240225B: CALET Gamma-Ray Burst Monitor detection
- GRB 240225B: Swift-XRT observations
- GRB 240226B: Fermi GBM Final Real-time Localization
- Transient EPW20240219aa: Kp-band imaging observations with NIRES
- Transient EPW20240219aa: J-band upper limits from WINTER
- GRB 240225C: CALET Gamma-Ray Burst Monitor detection
- GRB 240225B: GOTO detection of a candidate optical afterglow
- GRB 240226A: Fermi GBM Final Real-time Localization
- Transient EPW20240219aa: REM optical/NIR upper limits
- GRB 240225C: GRBAlpha detection
- GRB 240222A: ATCA radio observations
- Fermi trigger No 730618809: Global MASTER-Net observations report
- GRB 240225C: AstroSat CZTI detection
- GRB 240225B: AstroSat CZTI detection
- GRB 240225B: Tiled Swift observations
- GRB 240225B: MAXI/GSC detection
- Transient EPW20240219aa: Xinglong-2.16m optical upper limit
- GRB 240218A: VLA detection
- GRB 240225A: Swift/BAT-GUANO detection of a short burst
- GRB 240222A: GRBAlpha detection
- Transient EPW20240219aa: GECKO: LOAO Optical Upper Limits
- Transient EPW20240219aa: 7DT Optical Upper Limits
- Swift-BAT triggers 1217218-1217222 are not astrophysical
- VLA X-band observation of EPW20240219aa
- Transient EPW20240219aa: Mondy optical observations
- Transient EPW20240219aa: upper limit in gamma-ray range from SPI-ACS/INTEGRAL observations
- Insight-HXMT/HE Sub-Threshold Detection of Transient EPW20240219aa
- Swift BAT Sub-Threshold Detection of EPW20240219aa
- Transient EPW20240219aa: Liverpool Telescope non-detection and limiting magnitude
- GRB 240222A: GECAM detection of a burst
- GRB 240222A: Swift-BAT refined analysis
- GRB 240222A: Swift-XRT refined Analysis
- Swift-BAT triggers 1216907-1216911 are not astrophysical
- GRB 240222A: Fermi GBM Observation
- GRB 240222A: Swift/UVOT Upper Limits
- Fermi GBM Sub-Threshold Detection of EPW20240219aa as a likely GRB
- Swift GRB 240222A: Global MASTER-Net observations report
- Fermi GRB 240222A: Global MASTER-Net observations report
- EPW20240219aa is Likely a GRB Event
- Swift Trigger 1216864 is not an astrophysical event
- GRB 240222A: REM optical and NIR early-time observations
- GRB 240222A: Swift detection of a burst
- GRB 240222A: Fermi GBM Final Real-time Localization
- Swift-BAT triggers 1216751 and 1216753 are not astrophysical events
- Swift-BAT triggers 1216743-1216748 are not astrophysical
- Swift GRB240221.92: Global MASTER-Net observations report
- GRB 240218A: MeerLICHT upper limits
- GRB 240216A: Glowbug gamma-ray detection
- GRB 240215B: Fermi GBM Observation
- GRB 240218A: LBT H-band detection
- GRB 240218A: Swift-BAT refined analysis
- Fermi GRB 240220A: Global MASTER-Net observations report
- GRB 240220A: Fermi GBM Final Real-time Localization
- Konus-Wind detection of GRB 240218A
- GRB 240218A: Swift-XRT refined Analysis
- GRB 240218A: VLT/X-shooter redshift of z = 6.782
- GRB 240218A: Fermi GBM Detection
- GRB 240215A: Fermi GBM Observation
- GRB 240216A: GRBAlpha detection
- GRB 240215B: GRBAlpha detection
- IPN triangulation of GRB 240209A
- Fermi trigger No 729914426: Global MASTER-Net observations report
- GRB 240218A: VLT/FORS2 z-band detection
- GRB 240218A: Enhanced Swift-XRT position
- GRB 240218A: REM detection of a NIR afterglow candidate
- Gamma-ray flaring activity from the blazar 1ES 1959+650 observed by the Fermi-LAT
- GRB 240213A: GRBAlpha detection
- GRB 240218A : r-band upper limit from Observatoire de Haute-Provence
- GRB240218A: VLT/X-shooter upper limits
- GRB 240218A: Swift detection of a burst
- Swift GRB240218.08: Global MASTER-Net observations report
- GRB 240215C: Fermi GBM Final Real-time Localization
- GRB 240215B: Swift/BAT-GUANO detection of a burst outside the coded FOV
- Fermi GRB 240216A: Global MASTER-Net observations report
- Swift Triggers 12156887-1215690 are not astrophysical events.
- GRB 240216A: Fermi GBM Final Real-time Localization
- Fermi trigger No 729719508: Global MASTER-Net observations report
- GRB 240215A: Tiled Swift observations
- GRB 240215A: Swift/BAT-GUANO localization of a burst
- Fermi trigger No 729703985: Global MASTER-Net observations report
- Fermi trigger No 729650855: Global MASTER-Net observations report
- GRB 240209A: Classification of AT2024cew/GOTO24pw as Type Ia-pec supernova
- GRB 240209A: Fermi GBM observation
- GRB 240213A: Glowbug gamma-ray detection
- The AGILE satellite ceased operations and re-entered today into the atmosphere
- The AGILE satellite ceased operations and re-entered today into the atmosphere
- GRB240209A: OHP/T193 detection of the GOTO afterglow candidate AT2024cew / GOTO24pw
- GRB 240209A: Wendelstein Optical Observations
- GRB 240128A: Further Swift-XRT observations
- GRB 240214A: Tiled Swift observations
- GRB 240214A/1H 0451-560: MAXI/GSC detection