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"19257 results found.
- EP250901a: Mondy, Assy and SAO RAS optical limits
- GRB 250901A: Swift/UVOT Upper Limit
- GRB 250830B: Swift-XRT afterglow detection
- GRB 250901A: EP-FXT follow-up observation
- GRB 250901A: SVOM/VT optical afterglow with VHF data
- GRB 250901A: Swift-XRT afterglow detection
- EP250901a: Swift-XRT observations
- GRB 250901A: LCO optical upper limit
- EP250827b: Swift observations of AT 2025wkm
- GRB 250901A: SVOM detection of a burst
- EP250831a: EP-FXT follow-up observation
- EP250831a: Swift-XRT observations
- GRB 250831A: Swift-XRT counterpart detection
- GRB 250830B: Swift-XRT observations
- EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
- GRB 250830B: Swift ToO observations
- GRB 250830B: MAXI/GSC detection
- GRB 250828B: Swift-BAT refined analysis
- EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
- Swift GRB 250828B: Global MASTER-Net observations report
- EP250827a: Swift/UVOT Detection
- GRB 250828B: Swift detection of a burst
- EP250827a: confirmation of optical rebrightening with LCO
- EP250827a: Swift-XRT counterpart detection
- GRB 250823A: Swift-BAT refined analysis
- GRB 250823A: Swift-XRT refined Analysis
- LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
- GRB 250823A: COLIBRÍ optical observations
- GRB 250823A: SVOM/VT optical observation
- GRB 250823A: Swift/UVOT Detection
- GRB 250823A: NOT optical observations
- GRB 250823A: Fermi GBM Observation
- GRB 250818B: MeerKAT Detection
- GRB 250823A: Enhanced Swift-XRT position
- GRB 250823A: LCOGT Optical Detection
- GRB 250823A: BOOTES6/DPRT early optical detection
- GRB 250823A: Liverpool Telescope optical detection
- GRB 250823A: Swift detection of a burst
- Swift GRB250823.84: Global MASTER-Net observations report
- GRB 250821A: Kilonova-Catcher optical upper limits
- EP250821a: Swift/XRT counterpart fading
- GRB 250821A: Swift-BAT refined analysis
- EP250821a: Swift/UVOT further observations.
- GRB 250821A: VLT/FORS2 Optical Observation
- GRB 250821A: GECAM-B detection
- EP250821a: SVOM/VT optical observation
- GRB 250821A: NOT z-band upper limit
- GRB 250821A: Swift-XRT refined Analysis
- Swift GRB 250821A: Global MASTER-Net observations report
- GRB 250821A: Enhanced Swift-XRT position
- GRB 250821A: Swift/UVOT Upper Limits
- EP250821a: Rapidly fading optical source detected in Las Cumbres followup
- EP250821a: Swift XRT and UVOT counterpart detection
- GRB 250821A: LCOGT Optical Upper Limits
- GRB 250814A: CMO SAI and SAO RAS izJ observations.
- GRB 250821A: Prompt enhanced Swift-XRT position
- GRB 250821A: Swift detection of a burst
- LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
- GRB 250814A: Swift/UVOT Upper Limits
- GRB 250813B: Swift/UVOT Upper Limit
- IPN triangulation of GRB 250814C (short)
- IPN triangulation of GRB 250804B (short)
- GRB 250818B: Kilonova-Catcher optical afterglow detection
- GRB 250818A: AstroSat CZTI detection
- GRB 250818B: Swift/UVOT Detection
- GRB 250818B: SAO RAS optical observations
- Swift GRB 250818A: Global MASTER-Net observations report
- GRB 250818A: Swift-XRT refined Analysis
- GRB 250818A: Swift-BAT refined analysis
- GRB 250818B: Keck redshift of the optical afterglow
- GRB 250818A: Swift/UVOT Upper Limits
- GRB 250818A: Enhanced Swift-XRT position
- GRB 250818A: Fermi GBM Observation
- GRB 250818B: SVOM/VT optical observation
- GRB 250814A: Further GRAWITA TNG NIR observations
- GRB 250818B: Swift-XRT afterglow detection
- GRB 250818A: Swift detection of a burst
- sb25081602: Swift-XRT observations
- GRB 250814A: Swift-BAT refined analysis
- GRB 250814A: Further COLIBRÍ optical upper limit
- GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
- GRB 250814A: GRAWITA TNG NIR observations
- GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
- GRB250814A: TRT optical upper limits
- GRB 250814C: SVOM/GRM observation of a short burst
- LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
- GRB 250813B: SVOM/GRM observation
- GRB 250814A: P200/WIRC observations of the afterglow candidate
- GRB 250814A: possible optical afterglow candidate at Spanish observatories
- GRB 250814A: KAIT optical upper limit
- GRB 250814A: Swift-XRT refined Analysis
- GRB 240814A: Fermi GBM Observation
- GRB 250814A: Possible afterglow candidate from P200/WIRC
- GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
- Swift GRB250814.32: Global MASTER-Net observations report
- GRB 250814A: J-band upper limit from WINTER
- GRB 250813B: SVOM/VT optical observations
- GRB 250814A: COLIBRÍ optical upper limit
- LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
- GRB 250814A: DDOTI Optical Upper Limit