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').
Advanced Search
To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.
Advanced Search Examples (click to copy):
subject:"Swift"body:"GRB"submitter:"Judith Racusin"35423 results found.
- GRB 241029A: GTC/OSIRIS+ spectroscopic redshift z=1.072
- MISTRAL@OHP photometric and spectroscopic observations of GRB 241029A
- GRB 241026A: Swift/UVOT Upper Limits
- GRB 241029A: Swift-XRT observations
- GRB 241029A: Fermi GBM Observation
- GRB 241029A: AKO Optical Afterglow Detection
- GRB 241029A: GOTO optical afterglow detection
- GRB 241029A: MASTER early optical counterpart detection
- GRB 241029A: Xinglong-2.16m optical afterglow confirmation
- GRB 241029A: Mephisto observations
- EP 241026b: LBT possible optical counterpart (brightening source)
- GRB 241029A: TRT optical afterglow candidate detection
- GRB 241029A: Swift ToO observations
- GRB 241029A: SVOM/GRM observation
- GRB 241029A : Detection and localization of a bright long GRB by SVOM/ECLAIRs
- GRB 241029A: Fermi GBM Final Real-time Localization
- GRB 240821A: Keck/LRIS spectroscopic observations
- GRB 241026A: the 100th GRB detected by GRBAlpha
- GRB 241026A: TNOT optical counterpart detection
- Konus-Wind detection of GRB 241025A
- GRB 241025A (EP241025a): Optical afterglow observations with the Tsinghua-Nanshan Optical Telescope
- GRB 241026A: LBT redshift confirmation
- GRB 241026A: GECAM detection
- GRB 241025A: further SAO RAS optical observations
- GRB 241026A: BTA and Zeiss-1000 optical observations
- GRB 241026A: SVOM/GRM observation
- GRB 241025A: Swift/UVOT Detection
- GRB 241026A: GROWTH-India Telescope optical observations
- GRB 241026A Fermi GBM Analysis
- GRB 241026A: BTA redshift identification of z = 2.79
- 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: further SAO RAS optical observations
- EP241026a (GRB 241026A): EP on-board trigger and follow-up observation
- GRB 241026A: Swift-XRT refined Analysis
- GRB 241026A: Enhanced Swift-XRT position
- GRB 241026A: KAIT optical observations
- 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
- GRB 241026A: Fermi GBM Final Real-time Localization
- GRB241025A: 1.3m DFOT optical afterglow detection
- 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
- EP 241021a: Swift-XRT observations
- 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
- 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
- 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
- EP241021a: SAO RAS optical observations
- EP241021a: KAIT optical observations
- IPN triangulation of GRB 241021A (long)
- GRB 241018A: SVOM/C-GFT optical observations
- GRB241017A: 1.3m DFOT optical upper limit
- GRB 241018A: 1.3m DFOT Optical upper limit
- GRB 241018A: EP-FXT afterglow detection
- 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
- 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