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 241026A: J-band observations with WINTER
- GRB 241025A: SAO RAS optical observations
- GRB 241026A: Las Cumbres optical detection
- GRB 241025A: Mondy optical observations
- EP241021a: SOAR observations of the optical counterpart
- EP241021a: further SAO RAS optical observations
- EP241026a (GRB 241026A): EP on-board trigger and follow-up observation
- GRB 241026A: Swift-XRT refined Analysis
- EP 241026b: LBT optical observations
- EP241021a: e-MERLIN radio observation
- EP EP241026b: Global MASTER-Net observations report
- GRB 241026A: Enhanced Swift-XRT position
- GRB 241026A: KAIT optical observations
- EP241026b: EP detection of a fast X-ray transient
- Fermi trigger No 751616906: Global MASTER-Net observations report
- GRB 241026A: COLIBRÍ Detection of the Optical Counterpart
- GRB 241026A: SAO RAS observations of possible optical afterglow
- Fermi GRB 241026A: Global MASTER-Net observations report
- GRB 241026A: Prompt enhanced Swift-XRT position
- GRB 241026A: Swift detection of a burst
- Swift GRB241026.95: Global MASTER-Net observations report
- GRB 241026A: Fermi GBM Final Real-time Localization
- GRB241025A: 1.3m DFOT optical afterglow detection
- EP241021a: optical follow-up observations with Xinglong Observatory
- GRB 241025A: optical photometry from Konkoly
- GRB 241025A: GROWTH-India Telescope optical observations
- GRB 241025A: COLIBRÍ Detection of the Afterglow
- GRB 241025A: Swift-XRT refined Analysis
- GRB 241025C: Fermi GBM Detection
- GRB 241025A: Fermi GBM Observation
- IPN triangulation of GRB 241022A (short/hard)
- LIGO/Virgo/KAGRA S241009l: Upper limits from Swift/BAT-GUANO
- GRB 241025C: Fermi GBM Final Localization
- GRB 241025A: GRANDMA and Kilonova-Catcher optical afterglow detections and upperlimits
- GRB 241025B: Fermi GBM Final Localization
- Fermi trigger No 751563375: Global MASTER-Net observations report
- Fermi trigger No 751554401: Global MASTER-Net observations report
- EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
- EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
- EP 241021a: Swift-XRT observations
- EP241021a: optical follow-up observations with the Liverpool Telescope
- Fermi GRB 241025A: Global MASTER-Net observations report
- Swift GRB 241025A: Global MASTER-Net observations report
- EP241025a (GRB 241025A): EP observations update
- GRB 241025A : SVOM/VT optical afterglow observations
- EP 241021A: Swift ToO observations
- EP241021a: Liverpool Telescope optical follow-up observations
- GRB 241025A: Enhanced Swift-XRT position
- GRB 241001A: JWST spectroscopic identification of a supernova counterpart
- GRB 241025A: NOT spectroscopic redshift of z = 4.20
- GRB 241025A: DDOTI Afterglow detection
- EP241025a (GRB 241025A): EP on-board trigger and autonomous follow-up observation
- GRB 241025A: SVOM/GRM observation
- GRB 241025A: TRT optical afterglow observation
- Fermi GRB 241024B: Global MASTER-Net observations report
- GRB 241025A: Fermi GBM Final Real-time Localization
- GRB 241025A: Swift detection of a burst with an optical counterpart
- EP241021a: GTC OSIRIS+ spectroscopy of the optical counterpart
- GRB 241001A: ATCA radio observations
- GRB 241024B: Fermi GBM Final Localization
- EP241021a: No Detection in Fermi-GBM Observation
- GRB 241010A: VIRT Optical Upper Limit
- GRB 241024A: Fermi GBM Final Localisation
- EP241021a: VLT/FORS2 redshift z = 0.75
- Fermi trigger No 751449953: Global MASTER-Net observations report
- EP241021a: SAO RAS optical observations
- EP241021a: KAIT optical observations
- EP241021a: EP-FXT follow-up observation update
- IPN triangulation of GRB 241021A (long)
- EP241021a: Optical counterpart observations with the Liverpool Telescope
- EP241021a: 1.3m DFOT Optical observations
- EP241021a: GSP detects optical candidate counterpart
- EP241021a: Optical upper limits with Kinder observations
- EP241021a: TRT optical observations
- GRB 241018A: SVOM/C-GFT optical observations
- EP241021a: NOT likely optical counterpart
- EP EP241021a: Global MASTER-Net observations report
- GRB241017A: 1.3m DFOT optical upper limit
- GRB 241018A: 1.3m DFOT Optical upper limit
- GRB 241018A: EP-FXT afterglow detection
- EP241021a: GOTO optical upper limits
- EP241021a: EP detection of a fast X-ray transient
- IceCube-Cascade 241019A: Upper limits from a search for additional neutrino events in IceCube
- Konus-Wind detection of GRB 241018A
- GRB 241018A: SVOM/GRM observation
- GRB 241018A/sb24101802: Mephisto optical upper limit
- GRB 241017A/sb24101702: Mephisto optical upper limit
- GRB 241018A: BOOTES-4/MET optical upper limit
- GRB 241018A: Mondy optical upper limit
- GRB 241018A: SVOM/VT further analysis and counterpart confirmed
- GRB 241018A: GROWTH-India telescope optical upper limit
- GRB241018A: XingLong Optical Upper Limit
- GRB 241018A: Swift-XRT observations
- GRB 241018A: REM optical/NIR upper limits
- GRB 241018A: NOT optical observations
- GRB 241017A: SVOM/VT follow-up and optical upper limit
- GRB 241018A: SVOM/VT follow-up and optical candidate
- GRB 241018A: LCO/0.4m optical upper limits
- GRB 241018A: Swift ToO observations
- GRB 241006A: VIRT Optical Upper Limit