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"19325 results found.
- 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
- GRB 250813B: Swift-XRT afterglow detection
- GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
- EP250812a: NOT, NTT, and GS observations
- GRB 250812A: Swift/UVOT Detection
- EP250812a: SVOM/VT optical counterpart
- GRB 250812A: Swift ToO observations
- GRB 250807B: Swift-BAT refined analysis
- EP 250812a: GOTO optical upper limit
- GRB 250812A: Kilonova-Catcher optical afterglow detection
- EP250812a: Swift-XRT counterpart detection
- GRB 250812A: SVOM/VT optical afterglow confirmation
- GRB 250812A: Swift-XRT afterglow detection
- GRB 250809A: Swift-BAT refined analysis
- GRB 250807A: Swift-BAT refined analysis
- GRB 250809A: Swift/UVOT Detection
- Corrected Swift-XRT Refined Analysis of GRB 250809A
- GRB 250809A: Swift-XRT refined Analysis
- GRB 250807B: SVOM/VT optical observation
- GRB 250809A: LCOGT Optical Upper Limits
- GRB 250702B: Chandra X-ray Detection
- GRB 250808A: VLT X-shooter candidate counterpart
- GRB 250809A: Prompt enhanced Swift-XRT position
- GRB 250809A: Swift detection of a gamma ray burst
- GRB 250808A: Swift-XRT candidate counterpart detection
- GRB 250807A: SVOM/VT optical continued observation
- Konus-Wind detection of GRB 250807A
- GRB 250807B: Swift/UVOT Detection
- GRB 250807B: Kilonova-Catcher optical afterglow detection
- GRB 250807A: Swift/UVOT Detection
- GRB 250807A: Swift-XRT refined Analysis
- GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
- GRB 250806A: SVOM/MXT refined analysis