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"35321 results found.
- GRB 250322A: GRANDMA/TNOT optical upper limits
- GRB 250327A: SVOM/VT upper limits on the XRT position
- GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
- GRB 250327B: Las Cumbres optical counterpart detection
- GRB 250327B: Swift-XRT detection of the X-ray afterglow
- GRB 250327B: 1.6m Mephisto optical observations
- GRB 250327B: NOT spectroscopic redshift z = 3.035
- GRB 250327A: Swift-XRT refined Analysis
- GRB 250327B: GOTO optical counterpart detection
- GRB 250327B: SVOM/VT optically bright counterpart
- GRB 250327B: SAO RAS optical candidate
- GRB 250327B: SVOM detection of a burst
- GRB 250327A: J-band observations with WINTER
- GRB 250327A: SVOM/VT optical candidate
- GRB 250327A: Fermi GBM observation
- Fermi GRB 250327A: Global MASTER-Net observations report
- Swift GRB 250327A: Global MASTER-Net observations report
- GRB 250327A: DDOTI Optical Observations
- GRB 250327A: COLIBRÍ optical upper limit
- GRB 250327A: Swift detection of a burst
- GRB 250327A: Fermi GBM Final Real-time Localization
- Konus-Wind detection of GRB 250322A (short)
- IPN triangulation of GRB 250322B
- EP250321a: Mondy AZT-33IK Continued Optical Observations
- GRB 250322A: third epoch of NOT optical observations
- GRB 250322A: Swift-BAT refined analysis
- GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
- GRB 250322A: further NOT optical observations
- GRB 250322A: Swift/UVOT Upper Limits
- GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
- GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
- GRB 250321B: Swift-XRT observations
- GRB 250322A: Swift-XRT refined Analysis
- GRB 250322A: Gemini-North redshift of candidate host galaxy
- GRB 250322A: AstroSat CZTI detection of a short burst
- GRB 250322B: AstroSat CZTI detection of a bright long burst
- GRB250322A: STEP/T80S optical limits
- GRB 250322A: Gemini-South optical observations
- GRB 250322A: VLT optical observations
- GRB 250322A: VLT near-infrared observations
- GRB 250322A: NOT optical upper limits
- GRB 250322A: Enhanced Swift-XRT position
- GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
- GRB 250322A: MASTER optical observation
- EP250321a: Mondy AZT-33IK Optical Observations
- GRB 250322A: Swift detection of a short burst
- EP250321a: KAIT optical observations
- GRB 250225B: GECAM-A detection
- GRB 250312A: GECAM-A detection
- GRB 250321B: Swift ToO observations
- GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
- GRB 250321C: Fermi GBM Final Real-time Localization
- GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
- GRB 250320B: Fermi GBM Observation
- GRB 250321A: Swift-BAT refined analysis
- GRB 250321A: Swift-XRT refined Analysis
- GRB 250320B: Fermi-LAT detection
- GRB 250321B: SVOM detection of a sub-threshold transient event
- EP 250321A: Optical counterpart detection by LCO.
- GRB 250321A: Swift/UVOT Upper Limits
- GRB 250320B: SVOM/GRM observation of a long burst
- GRB 250320B: AstroSat CZTI detection
- Fermi GRB 250320B: Global MASTER-Net observations report
- Swift GRB 250321A: Global MASTER-Net observations report
- Fermi GRB 250321A: Global MASTER-Net observations report
- GRB 250321A: GOTO optical upper limits
- GRB 250321A: Swift-XRT localisation
- GRB 250314A: Keck/NIRC2 J-band upper limit
- EP250226a/GRB 250226A: KAIT optical observations
- GRB 250321A: Fermi GBM Observation
- GRB 250321A: Swift detection of a burst
- GRB 250321A: Fermi GBM Final Real-time Localization
- GRB 250320B: Fermi GBM Final Real-time Localization
- GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
- GRB 250317B: Mondy AZT-33IK Continued Optical Observations
- GRB 250320A: Fermi GBM Final Real-time Localization
- Fermi GRB 250319B: Global MASTER-Net observations report
- GRB 250313A: GRBAlpha detection
- GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
- GRB 250319B: Fermi GBM Final Localization
- GRB 250319A: Fermi GBM Final Localization
- GRB 250317D: EIRSAT-1 GMOD Detection
- GRB 250314A: ATCA radio upper limits
- GRB 250317B: OHP/T193 continued follow-up
- GRB 250317C: SVOM/GRM observation of a long burst
- GRB 250317B: Leavitt Observatory optical upper limit
- GRB 250309B/AT2025dws: further ATCA observations
- GRB 250317B: Mondy AZT-33IK Optical Observations
- GRB 250317C: AstroSat CZTI detection
- GRB 250317B: NOT optical observations suggest an optical plateau phase
- GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
- GRB 250317C: GECAM-B detection
- GRB 250317B: OHP/T193 optical observations
- GRB250312A: Swift/UVOT Upper Limits
- GRB 250317B: REM optical/NIR observations
- GRB 250317B: Swift-XRT observations
- GRB 250316A: Swift/UVOT Upper Limits
- GRB 250314A: REM optical/NIR upper limits
- GRB 250316A: AbAO AS-32 Optical Upper Limit
- EP 250317B: Fading optical counterpart detection by LCO