GCN Circulars
GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"- Swift GRB 250114A: Global MASTER-Net observations report
- GRB 250114A: Swift detection of a burst with an optical counterpart
- GRB 250101A: Terskol Zeiss-2000 optical observations
- EP250108a / AT 2025kg: SAO RAS optical observations
- EP241021a: SMA radio observation
- GRB 250113A: SVOM/GRM observation of a long burst
- GRB 250107A: VZLUSAT-2 detection
- EP250109b: optical upper limits with the Liverpool Telescope
- GRB 250109A / EP250109a: GRBAlpha detection
- GRB 250107D: GRBAlpha detection
- GRB 250106A: Swift-XRT afterglow detection
- Fermi trigger No 758442826: Global MASTER-Net observations report
- EP250111a: KAIT optical observations
- GRB 250109A / EP250109a: Mephisto optical upper limits
- EP250108a: Mephisto detection
- EP250111a: Mondy optical observation
- EP250108a / AT 2025kg: LCO optical observations
- EP250111a: Global MASTER-Net observations report
- EP250111a: Swift/XRT detection and fading
- EP250108a / AT 2025kg: Swift UVOT detections
- EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
- EP250108a: optical follow-up observations with the Liverpool Telescope
- EP250111a: NOT likely optical counterpart
- EP250111a: a new X-ray transient detected by Einstein Probe
- EP250109a/GRB 250109A:SVOM/VT optical counterpart
- GRB 250101B: Fermi GBM Observation
- EP250108a: further NOT optical observations
- GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
- GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
- GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
- GRB 250108A: Swift/XRT afterglow fading
- GRB 250107D: CALET Gamma-Ray Burst Monitor detection
- GRB 250107C: CALET Gamma-Ray Burst Monitor detection
- Konus-Wind detection of GRB 250107C
- LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
- LIGO/Virgo/KAGRA S250109f: Updated Sky localization
- LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
- EP-WXT trigger EP250108a：Xinglong optical follow-up observations
- GRB 250101A: CMO RC-500 optical observations
- EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
- EP250108a: EP-FXT follow-up observation
- GRB 250109A: Fermi GBM Observation
- The EP-WXT trigger 01709130111 is likely a flaring star
- EP250108a: NOT optical observations
- EP-WXT trigger EP250109a：Xinglong optical follow-up observations
- GRB 250109a: GMG Optical Upper Limit
- EP250109a: Swift/UVOT non-detection
- Konus-Wind detection of GRB 250107D (short/hard)
- IPN triangulation of GRB 250107D (short/hard)
- IPN triangulation of GRB 250107C
- EP250108a: Liverpool Telescope likely optical counterpart
- GRB 250108B: Gemini-North likely redshift z = 2.197
- GRB 250108B: Swift-BAT refined analysis
- GRB 250108B: 1.3m DFOT upper limit
- GRB 250108B: REM optical/NIR upper limits
- GRB 250109A /EP250109a: Fermi GBM Final Localization
- EP250109a: SVOM/VT optical candidate
- EP250109a: Global MASTER-Net observations report
- GRB 250107C: SVOM/GRM observation
- GRB 250101A: Terskol K-800 optical observations
- EP250109a: GOTO optical upper limits
- EP250109a: Swift/XRT non-detection
- GRB 250108A: Swift/UVOT Upper Limits
- EP250108a: Global MASTER-Net observations report
- EP250109a: EP-WXT detection of an X-ray transient
- LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
- GRB 250108A: NOT optical upper limit
- EP250108a: EP-WXT detection of an X-ray transient
- LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
- GRB 250108B: Swift-XRT refined Analysis
- Swift GRB 250108B: Global MASTER-Net observations report
- Fermi Gamma-ray Burst Monitor trigger 758061038/250108855 is not a GRB
- LIGO/Virgo/KAGRA S250108ha: Retraction of GW compact binary merger candidate
- GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
- GRB 250103A: 1.6m Mephisto optical observations
- GRB 250108A: Swift-XRT afterglow detection
- GRB 250108A:SVOM/VT optical candidate
- LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
- GRB 250108B: Swift/UVOT Upper Limits
- GRB 250103A: Swift-XRT afterglow detection
- GRB 250108B: Enhanced Swift-XRT position
- GRB 250108B: Swift detection of a burst
- GRB 250108A: Swift ToO observations
- GRB 250108A: SVOM detection of a soft long burst
- GRB 250107A: Fermi GBM Observation
- GRB 241228B: Fermi-LAT detection
- Fermi GRB 250107B: Global MASTER-Net observations report
- GRB 250107A: Swift ToO observations
- GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
- GRB 250107B: Fermi GBM Final Real-time Localization
- GRB 250106A: SVOM/VT 2nd optical deep observation
- GRB 250101A: J band upper limit by SYSU 80cm telescope
- GRB 250107A: Fermi GBM Final Real-time Localization
- EPWXT01709129925: Xinglong optical observations
- GRB 250106A: NOT optical observations
- LIGO/Virgo/KAGRA S250104v: Updated Sky localization
- GRB 250103B: REM optical/NIR upper limits
- GRB 250101A: REM optical/NIR counterpart detection
- GRB 250106A: Swift-XRT observations
- GRB 250106A: SVOM/VT optical candidate