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"- GRB 260926A: GECAM-B observation
- EP260927a: Global MASTER-Net observations report
- EP260927a: Einstein Probe detection of a fast X-ray transient
- GRB 260926B: Glowbug gamma-ray detection of a likely short burst
- GRB 260926A: Glowbug gamma-ray detection
- GRB 260924A: VLA detection
- GRB 260924A: Swift/UVOT UV grism spectrum results
- GRB 260924A: AbAO optical observations
- Fermi GRB 260928A: Global MASTER-Net observations report
- GRB 260928A: Fermi GBM Final Real-time Localization
- EP260924a: Global MASTER-Net observations report
- GRB 260925A: Swift-BAT refined analysis
- Swift Trigger 1513439: consistent with noise and not astrophysical
- GRB 260924A: Upper limits from a neutrino search with IceCube
- Fermi GRB 260926C: Global MASTER-Net observations report
- GRB 260926C: Fermi GBM Final Real-time Localization
- GRB260914A: MAO/AZT-22 optical observations
- GRB 260926B: Fermi GBM Final Real-time Localization
- Fermi GRB 260926A: Global MASTER-Net observations report
- GRB 260924A: Near-infrared detection with MDM/MIRAGE
- GRB 260926A: Fermi GBM Final Real-time Localization
- The EP-WXT trigger 01709320726 is likely a flaring star
- GRB 260924A: COLIBRÍ optical observations
- GRB 260924A: Second-epoch J-band upper limit from the SYSU 80 cm infrared telescope
- EP260924a: J-band upper limit by SYSU 80cm infrared telescope
- GRB 260925A: J-band upper limit by SYSU 80cm infrared telescope
- GRB 260925A: Swift-XRT refined Analysis
- EP260924a: EP-FXT follow-up observation
- Swift Trigger 1513439 is probably not a GRB
- GRB 260925A: Swift/UVOT Upper Limits
- Konus-Wind detection of GRB 260924A
- GRB 260924A: Extreme Isotropic-equivalent Gamma-ray Energy and encouragement for multiwavelength follow-up observations
- GRB 260923A: Glowbug gamma-ray detection
- GRB 260924A: Optical follow-up observations with Kinder
- GRB 260922A: Glowbug gamma-ray detection
- GRB 260925A: Enhanced Swift-XRT position
- GRB 260925A: COLIBRÍ optical upper limits
- GRB 260925A: FRAM-Auger optical limit
- GRB 260924A: Ondrejov D50 optical afterglow detection
- EP260924a: J-band upper limit with WINTER
- GRB 260924A: SVOM/GRM observation
- GRB 260924A: 2.2m CAHA spectroscopic redshift z = 3.51
- GRB 260925A: Swift detection of a burst
- GRB 260923A: Insight-HXMT/HE detection
- EP260924a: EP-WXT detection of an X-ray transient
- GRB 260924A: J-band observations by the SYSU 80 cm infrared telescope
- GRB 260924A: Swift/UVOT Detection
- GRB 260924A: GROWTH-India Telescope optical observations
- GRB 260924A: Swift-BAT refined analysis
- GRB 260924A: NuSTAR detection of prompt emission
- GRB 260924A: Swift/UVOT Upper Limits
- GRB 260924A: Swift-XRT refined Analysis
- Konus-Wind detection of GRB 260922A
- GRB 260922A: NuSTAR detection of prompt emission
- GRB 260921A: NuSTAR detection of prompt emission
- Konus-Wind detection of GRB 260921A (correction to GCN 45722)
- GRB 260921A: SVOM/GRM observation
- GRB 260922A: COLIBRÍ Confirmation of the Optical Counterpart
- GRB 260924A: Fermi GRB Observation
- Konus-Wind detection of GRB 260921A (possible merger-origin)
- GRB 260924A: Fermi-LAT detection of a bright burst
- GRB 260924A: AstroSat CZTI detection
- GRB 260920A: SVOM/GRM observation
- GRB 260924A: NOT optical counterpart confirmation
- GRB 260924A: detection of a bright optical afterglow by the 1.5m OSN telescope
- GRB 260922A: CALET Gamma-Ray Burst Monitor detection
- GRB 260924A: Enhanced Swift-XRT position
- The EP-WXT trigger 01709319842 is likely a flaring star
- GRB 260924A: Swift detection of a burst
- GRB 260924A: Fermi GBM Final Real-time Localization
- Fermi GRB 260923A: Global MASTER-Net observations report
- GRB 260923A: Fermi GBM Final Real-time Localization
- Trigger_21914: Swift ToO observations
- EP260806a: e-MERLIN detection at 5 GHz
- GRB 260922A: Ondrejov D50 optical limit
- Fermi-LAT Gamma-ray Observations of IceCube-260919A
- Fermi-LAT Gamma-ray Observations of IceCube-260916A
- ATCA observations of GRB 260909A
- GRB 260922A: Swift-BAT refined analysis
- EP260920a: VLT/HAWK-I near-infrared counterpart confirmation
- GRB 260922A: J-band upper limit with WINTER
- GRB 260922A: Swift/UVOT Upper Limits
- GRB 260922A: COLIBRÍ Optical Counterpart Candidate (correction to GCN 45698)
- GRB 260922A: COLIBRÍ optical upper limits
- GRB 260922A: Swift-XRT refined Analysis
- GRB 260922A: Enhanced Swift-XRT position
- Fermi-LAT Gamma-ray Observations of IceCube-260805A
- Konus-Wind detection of GRB 260810A
- GRB 260920A: Glowbug gamma-ray detection
- GRB 260918A: SVOM/ECLAIRs refined analysis
- GRB 260922A: SVOM/C-GFT optical upper limit
- GRB 260922A: Swift detection of a burst
- GRB 260917C: AstroSat CZTI detection
- GRB 260920B/EP260920b: GECAM-B detection of a burst
- GRB 260921A: AstroSat CZTI detection
- GRB 260921A: Swift-BAT refined analysis
- GRB 260921B: Fermi GBM Final Localization
- GRB 260921A: Fermi GBM Observation
- EP260920b: 2.2m CAHA optical afterglow detection and 10.4m GTC redshift confirmation
- EP Alert 260921.58: Global MASTER-Net observations report