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"27782 results found.
- Swift GRB250101.56: Global MASTER-Net observations report
- GRB 241217a/EP241217b: ATCA Radio Detection
- EP241217a: VLA Radio Detection
- GRB 241229A: EP-FXT X-ray afterglow confirmation
- GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
- GRB 241229B: SVOM/GRM observation
- EP241217A: J band upper limit by SYSU 80cm telescope
- GRB 241228B: SAO RAS optical observations
- GRB 241229B: SVOM/VT optical candidate
- GRB 241229A: Swift-XRT observations
- Konus-Wind detection of GRB 241228A
- GRB 241229A: EP-FXT afterglow candidates
- EP240702a: 7DT Optical upper limits
- GRB 240606B: 7DT Optical upper limits
- GRB 241229B: Swift-BAT refined analysis
- GRB241229B: UVOT upper limits
- GRB 241229C: Fermi GBM Final Real-time Localization
- GRB 241228B: D50 optical detection
- GRB 241228B: Fermi GBM Observation
- GRB 241228B: Swift-XRT afterglow detection
- GRB 241229B: Fermi GBM Observation
- GRB 241229A: Swift ToO observations
- GRB 241229B: Swift-XRT refined Analysis
- IceCube-241224A: No transient candidates from the Zwicky Transient Facility
- Swift GRB 241229B: Global MASTER-Net observations report
- GRB 241228B: VLT/X-shooter redshift of z = 2.674
- GRB 241228A: NOT optical upper limits
- GRB 241228A: Swift-BAT refined analysis
- GRB 241228B: Swift/BAT-GUANO localization skymap of a burst
- GRB 241229B: Swift detection of a burst
- GRB 241229B: Fermi GBM Final Real-time Localization
- GRB 241229A: SVOM detection of a long burst
- GRB 241228A: Fermi GBM Observation
- Swift GRB 241228A: Global MASTER-Net observations report
- GRB 241226A: Swift/BAT-GUANO localization skymap of a burst
- GRB 241228A: GROWTH-India telescope optical upper limit
- GRB 241228B: Swift ToO observations
- GRB 241228A: Swift-XRT refined Analysis
- GRB 241228A: Swift/UVOT Upper Limits
- GRB 241228A: Enhanced Swift-XRT position
- GRB 241228B: Fermi GBM Final Real-time Localization
- GRB 241228A: Swift detection of a burst
- GRB 241223A: GRBAlpha detection
- GRB 241212A: VZLUSAT-2 detection
- GRB 241226A: Fermi GBM Final Real-time Localization
- GRB 241029A: LCO optical observation
- GRB 241223A: Swift-XRT observations
- GRB 241223A: Fermi GBM Detection
- EP241223a
- IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
- EP241223a: EP-WXT detection of a fast X-ray transient
- EP241113a: Non-detection in Radio Follow-up Observations with eMERLIN
- GRB241113A: 7DT Optical upper limits
- GRB 241223A: GOTO optical observations summary
- GRB 241223A: Swift ToO observations
- EP241217a: e-MERLIN radio observations
- GRB 241223A: Fermi GBM Final Real-time Localization
- GRB 241217A / EP241217b: Non-detection in ATCA Radio Follow-up Observations
- GRB 241209B: host galaxy detection and GTC/OSIRIS+ spectroscopy
- GRB 241221A: Fermi GBM Final Real-time Localization
- GRB 241217A/EP241217b: SOAR afterglow detection
- EP241021a: VLA radio detection
- GRB 241218A: Mondy AZT-33IK optical upper limit
- GRB 241217A/EP241217b: tentative VLT spectroscopic redshift z=1.879
- EP241217a: 1.6m Mephisto multi-band optical observations
- GRB 241218A: Swift/UVOT Upper Limits
- EP241217a: optical upper limit with the Liverpool Telescope
- GRB 241209B: EP-FXT afterglow detection
- Konus-Wind detection of GRB 241204A (short/hard)
- GRB 241218A: NOT optical upper limits
- GRB 241218A: Swift-BAT refined analysis
- EP 241217a: NIR detection with P200/WIRC
- EP 241217a: Possible J-band detection with WINTER
- GRB 241217A/EP241217B: Fermi-GBM Sub-Threshold Detection
- EP241217a: refined EP-WXT analysis and EP-FXT follow-up observations
- GRB 241217A: refined SVOM/MXT data analysis. Long lasting X-ray emission.
- GRB 241218A: REM optical upper limit
- GRB 241217A/EP241217b: REM optical/NIR upper limits
- EP241217a: REM optical/NIR upper limits
- GRB 241218a: Liverpool Telescope optical follow-up
- GRB 241217a: Liverpool Telescope optical follow-up
- EP241217a: Liverpool Telescope optical follow-up
- GRB 241218A: Swift-XRT refined Analysis
- EP241119a: 7DT Optical upper limits
- GRB 241209A: ATCA radio follow-up observations
- EP241217b/GRB 241217A: EP detection of the prompt X-ray emssion
- GRB 241218A: LCOGT Optical Upper Limit
- GRB 241218A: Enhanced Swift-XRT position
- GRB 241218A: Swift detection of a burst
- GRB 241217A : SVOM/VT optical afterglow detection
- GRB 241217A: Swift-XRT afterglow detection
- EP241217a: Swift-XRT Detection
- EP241217A: Non-detection from Fermi-GBM Observations
- GRB 241217A : SVOM/ECLAIRs,GRM,MXT detection of a long burst with a bright X-ray afterglow candidate
- EP241217a: Gemini-North spectroscopic redshift z = 4.59
- GRB 241214A: GRBAlpha detection
- GRB 241213A (EP241213a): GRBAlpha detection
- GRB 241209D: GRBAlpha detection
- EP241217a: Gemini-North detection of the likely optical counterpart
- EP241217a: EP detection of an X-ray transient