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"36283 results found.
- GRB 260207A: Fermi GBM Final Localization
- EP260131a: VLA detection
- GRB 260206A: Tiled Swift observations
- GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
- GRB 260204A: SVOM/VT confirms fading of the optical afterglow
- GRB 260204A: Swift-XRT observations
- GRB 260204A: LCO optical afterglow detection
- GRB 260204A: SVOM/VT optical candidate
- GRB 260204A : MASTER Global robotic net optical observations
- Fermi GBM Sub-Threshold Detection of GRB 260204A
- GRB 260204A: GOTO optical upper limit
- GRB 260204A: LCO optical upper limits
- GRB 260204B: Fermi GBM Final Real-time Localization
- GRB 260204A: SVOM detection of a burst
- GRB 260121A: 239Alferov CubeSat detection
- Konus-Wind detection of GRB 260121A
- GRB 260131A/B: OHP/T193 optical observations
- GRB 260131A: KAIT optical observations
- GRB 251230A: MeerLICHT afterglow detection
- GRB 260131A: FTW optical and NIR observations
- GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
- GRID detection of GRB 260131A/B
- GRB 260131A/B: GTC/OSIRIS+ redshift confimation
- GRB 260130A: Insight-HXMT/HE detection
- GRB 260130A: GECAM-B observation of a short burst
- GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
- GRB 260131A/B: EP/FXT X-ray afterglow detection
- GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
- GRB 260127B: Insight-HXMT/HE detection
- GRB 260127B: GECAM-B observation of a short burst
- GRB 260127A: GECAM-B observation
- GRB 260131A: NOT spectroscopic redshift z = 1.434
- EP260131a: Liverpool Telescope optical upper limits
- Konus-Wind detection of GRB 260128A / EP260128a
- GRB 260131A: Insight-HXMT/HE detection
- Konus-Wind detection of GRB 260131A/B
- GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
- GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
- GRB 260131A/B: Fermi GBM Observation
- EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
- EP260131a: NOT early detection of the counterpart in "rapid response mode"
- GRB 260131B: MAXI/GSC detection
- GRB 260131A: Fermi GBM Final Real-time Localization
- GRB 260127B: AstroSat CZTI detection
- GRB 260130A: Fermi GBM Detection
- GRB 260127B: Fermi GBM Detection
- EP260128a / GRB 260128A: COLIBRÍ optical upper limit
- Fermi GRB 260130A: Global MASTER-Net observations report
- EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
- GRB 260130A: Fermi GBM Final Real-time Localization
- Fermi GRB 260129A: Global MASTER-Net observations report
- GRB 260128B: LCO optical upper limits
- GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
- IPN triangulation of GRB 260121A
- GRB 260127A: Swift-BAT refined analysis
- GRB 260129B: Fermi GBM Final Localization
- GRB 260128B: SVOM detection of a burst through offline search
- GRB 260129A: Fermi GBM Final Localization
- IPN triangulation of GRB 260127B (short)
- GRB 260127B: Swift-XRT observations
- GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
- GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
- Fermi GRB 260127A: Global MASTER-Net observations report
- GRB 260127A: Fermi GBM Observation
- GRB 260127A: COLIBRÍ optical observations
- GRB 260127A: NOT optical observations
- GRB 260127B: Swift ToO observations
- GRB 260127A : MITSuME Akeno optical afterglow candidate detection
- GRB 260127A: Swift-XRT refined Analysis
- GRB 260127B: GOTO candidate optical counterpart
- GRB 260127A: SVOM/C-GFT optical observations
- GRB 260127A: Enhanced Swift-XRT position
- Fermi GRB 260127B: Global MASTER-Net observations report
- GRB 260127B: Fermi GBM Final Real-time Localization
- GRB 260127A: Prompt enhanced Swift-XRT position
- Swift GRB 260127A: Global MASTER-Net observations report
- GRB 260127A: LCO optical afterglow discovery
- GRB 260127A: Swift detection of a burst
- GRB 260127A: Fermi GBM Final Real-time Localization
- GRB 260125A: Swift-XRT observations
- EP260126a: Optical upper limit with Kinder observations
- GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
- Konus-Wind detection of GRB 260120B
- GRB 251222A: SVOM/ECLAIRs refined analysis
- GRB 260125A: Swift ToO observations
- GRB 260125A: GOTO candidate optical counterpart
- Fermi GRB 260125B: Global MASTER-Net observations report
- GRB 260125B: Fermi GBM Final Real-time Localization
- GRB 260125A: Fermi GBM Final Real-time Localization
- GRB 260114A: SVOM/VT optical upper limits
- GRB 260120A: AstroSat CZTI detection
- GRB 260122B: Swift-BAT refined analysis
- GRB 260120B: SVOM/GRM observation
- GRB 260120A: GECAM-B observation
- GRB 260120B: AstroSat CZTI detection
- GRB 260114A: Insight-HXMT/HE detection
- GRB 260122B: Swift detection of a burst
- EP260119a: Assy AZT-20 optical observations
- EP260119a: Mondy and SAO RAS optical upper limits
- GRB 260122A: Fermi GBM Final Real-time Localization