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"- Fermi GRB 260523A: Global MASTER-Net observations report
- GRB 260523B: Fermi GBM Final Real-time Localization
- GRB 260523A: Fermi GBM Final Real-time Localization
- GRB 260522A: Fermi GBM Observation
- GRB 260522B: NuSTAR detection of prompt emission
- EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
- GRB 260522B: Fermi GBM Final Real-time Localization
- GRB 260522A: GOTO optical upper limit
- Fermi trigger No 801135305: Global MASTER-Net observations report
- Fermi GRB 260522A: Global MASTER-Net observations report
- EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
- GRB 260522A: Fermi-LAT detection
- GRB 260519C: SVOM/GRM observation
- GRB 260522A: Fermi GBM Final Real-time Localization
- GRB 260511A: iTelescope T-75 optical detection
- GRB 260520B: SVOM/GRM observation
- GRB 260411B: TERI Gamma-ray detection
- GRB 260407A: TERI Gamma-ray detection
- GRB 260307A: TERI Gamma-ray detection
- GRB 260225D: TERI Gamma-ray detection
- GRB 251118A: TERI Gamma-ray detection
- GRB 251113A: TERI Gamma-ray detection
- GRB 260428A: TERI Gamma-ray detection
- Konus-Wind detection of GRB 260519C
- GRB 260520B: Fermi GBM Final Localization
- GRB 260509A: SVOM/ECLAIRs refined analysis
- GRB 260520A: Fermi GBM Final Localization
- GRB 260519D: Fermi GBM Final Localization Correction
- GRB 260519C: NuSTAR detection of prompt emission
- Konus-Wind detection of GRB 260518A
- GRB 260519B: Fermi GBM Final Localization
- GRB 260519A: Fermi GBM Final Localization
- GRB 260518A: AstroSat CZTI detection of a long burst
- GRB 260516D: SVOM/ECLAIRs refined analysis
- GRB 260515A: SVOM/ECLAIRs refined analysis
- GRB 260421B: radio detection with the VLA
- GRID detection of GRB 260511A
- GRB 260509A: CrAO ZTSh optical upper limit (Duplicate Submission)
- GRB 260509A: CrAO ZTSh optical upper limit
- GRB 260516D: EP-FXT follow-up observation
- GRB 260516D: GOTO optical counterpart detection
- GRB 260516D: LCO optical observations
- GRB 260515A: further Liverpool Telescope observations
- GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
- GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
- GRB 260516D: GROWTH-India Telescope optical detection
- GRB 260516D: SVOM/VT optical bright candidate
- GRB 260516D: FRAM-ORM optical limit
- GRB 260515A: CrAO ZTSh BVRI optical observations
- Fermi GRB 260516C: Global MASTER-Net observations report
- SVOM GRB260516D: Global MASTER-Net observations report
- GRB 260516D: SVOM possible detection of a burst
- GRB 260516C: Fermi GBM Final Real-time Localization
- Konus-Wind detection of GRB 260515A
- GRB 260515A: Liverpool Telescope optical detection
- GRB 260515A: LCO optical counterpart detection
- Fermi Gamma-ray Burst Monitor trigger 800627191/260516518 is not a GRB
- GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
- GRB 260515A: EP-FXT follow-up observation
- EP260514a: refined analysis of the EP-WXT and follow-up EP-FXT observations
- EP260514a: NOT optical counterpart confirmation
- EP260514a: TRT optical counterpart candidate
- EP260514a: SVOM/VT optical candidate
- Fermi GRB 260516B: Global MASTER-Net observations report
- GRB 260516B: Fermi GBM Final Real-time Localization
- Fermi Gamma-ray Burst Monitor trigger 800592653/260516119 is not a GRB
- GRB 260515A: SVOM/VT optical observations
- GRB 260515A: OHP/T193 optical observations
- EP260514a: COLIBRÍ optical upper limits
- GRB 260516A: Fermi GBM Final Real-time Localization
- GRID detection of GRB 260507A
- GRB 260515A: GTC/OSIRIS+ spectroscopic redshift z = 0.764
- GRB 260515A: LCO optical observations
- SVOM GRB 260515A: Global MASTER-Net observations report
- GRB 260515A: NOT optical observations.
- SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
- GRB 260515A: SVOM/VT optical candidate from VHF data
- GRB 260515A: JinShan optical counterpart candidate
- GRB 260515A: SVOM detection of a burst
- GRB 260510C: Glowbug gamma-ray detection
- IceCube-260504A: No Candidate Transients from the Zwicky Transient Facility
- EP260514a: GROWTH-India Telescope optical upper limit
- GRB 260511B: NOT optical observations
- Konus-Wind detection of GRB 260512A
- GRB 260510C: CALET Gamma-Ray Burst Monitor detection
- GRB 260511B: GMG Optical Upper Limit
- EP260514a: Global MASTER-Net observations report
- EP260514a: Einstein Probe detection of a fast X-ray transient
- EP260512a: LCO optical upper limits
- IPN triangulation of GRB 260512A
- GRB 260511B: Mephisto multi-band optical followup
- Fermi GRB 260514A: Global MASTER-Net observations report
- GRB 260512A: AstroSat CZTI detection
- The EP-WXT trigger 01709262077 is likely a flaring star
- EP260512a: EP-FXT follow-up observation
- EP260507a: Xinglong Schmidt optical counterpart detection
- GRB 260514A: Fermi GBM Final Real-time Localization
- EP260512a: Global MASTER-Net observations report
- Fermi GRB 260513A: Global MASTER-Net observations report
- Fermi GRB 260512A: Global MASTER-Net observations report