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.
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"
18004 results found.
- GRB 250702F: Leavitt Observatory optical observations
- GRB 250702F: AKO Optical Afterglow Detection
- GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
- GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
- GRB 250702F: Skynet Optical Observations
- GRB 250424A: VIRT Optical Upper Limit
- GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
- GRB 250702F: TRT Optical Observation
- GRB 250703A: DDOTI Optical Upper Limit
- GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
- GRB 250702F: REM optical afterglow detection
- GRB 250702F: DDOTI Optical Observation
- GRB 250702F: COLIBRÍ Observations of the Afterglow
- EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
- GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
- GRB 250702F: Enhanced Swift-XRT position
- GRB 250702F: NOT observations of the optical afterglow
- GRB 250702F: Ondrejov D50 optical afterglow detection
- GRB 250702F: Swift detection of a burst with an optical counterpart
- LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
- GRB 250628B: EP-FXT counterpart detection
- LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
- GRB 250628A: REM optical/NIR upper limits
- LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
- GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
- GRB 250628A: VLT/X-shooter upper limits
- GRB 250628A: Swift/UVOT Upper Limits
- GRB 250628A: Enhanced Swift-XRT position
- GRB 250628A: Swift detection of a burst
- GRB 250625A: Leavitt Observatory afterglow detection
- GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
- GRB 250625A: SVOM/C-GFT upper limit in early phase
- GRB 250625A: GECAM-B detection
- GRB 250625A: Swift/UVOT Upper Limits
- GRB 250625A: ABObservatory afterglow detection
- GRB 250625A: OHP/T193 optical detection
- GRB 250625A: COLIBRÍ optical observations
- GRB 250625A: Swift-XRT refined Analysis
- GRB 250625A: JinShan optical observations
- GRB 250625A: SAO RAS possible optical afterglow
- GRB 250625A: Enhanced Swift-XRT position
- GRB 250625A: Swift detection of a burst
- GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
- GRB 241018A: Maidanak optical observations
- sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
- IPN triangulation of GRB 250620С (long/bright)
- GRB 250620C: SVOM/GRM observation
- GRB 250620A: SVOM/GRM observation of a short burst
- GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
- GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
- GRB 250506A - SVOM/ECLAIRs Refined analysis
- GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
- GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
- EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
- GRB 250617B: Nickel telescope optical observations
- GRB 250615A: Kilonova-Catcher optical upper limits
- GRB 250617B: Assy AZT-20 Optical Observations
- sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
- GRB 250617B: Swift/UVOT Detection
- GRB 250617B: Kilonova-Catcher optical afterglow detection
- GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
- GRB 250617B: COLIBRÍ optical observations
- GRB 250617B: NOT NIR observations of the afterglow
- GRB 250617B: NUTTelA-TAO early time optical observations
- GRB 250617B: Enhanced Swift-XRT position
- GRB 250617B: SAO RAS optical observations
- GRB 250617B: Swift detection of a burst with an optical counterpart
- GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
- EP-WXT trigger 01709178975: GOTO optical upper limit
- Konus-Wind detection of GRB 250615A / EP250615a
- SVOM sb25061207: AbAO AS-32 Optical Upper Limit
- GRB 250615A: COLIBRÍ optical upper limit
- GRB 250615A: DDOTI Optical Upper Limit
- GRB 250615A: Swift/UVOT Upper Limits
- Konus-Wind detection of GRB 250612C (short/hard with extended emission)
- GRB 250615A: Swift-XRT refined Analysis
- sb25061207/SVOM: T120 OHP optical upper limit
- EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
- GRB 250615A: Enhanced Swift-XRT position
- GRB 250615A: Swift detection of a burst
- GRID detection of GRB 250612C
- sb25061207: Mephisto optical upper limits
- EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
- sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
- sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- EP250612a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
- EP250612a: SVOM/VT optical candidate
- GRB 250612C: Fermi GBM Observation
- sb25061207: Swift-XRT observations
- EP250612a/GRB 250612B: JinShan optical upper limit
- sb25061207: SVOM/VT optical counterpart
- GRB 250610B: Swift-XRT refined Analysis
- EP250612a: Einstein Probe detection of an X-ray transient
- GRB 250610B: MISTRAL/T193 and T120 OHP further observations
- sb25061207: SVOM detection of a X-ray transient
- GRB 250610B - SVOM/ECLAIRs refined analysis
- Swift GRB250612.04: Global MASTER-Net observations report