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 251013C: ABObservatory optical observations
- GRB 251014A: SAO RAS optical upper limit
- GRB 251014A: Fermi GBM Observation
- GRB 251013C: J band observations by SYSU 80cm infrared telescope
- GRB 251013C: EP-FXT counterpart detection
- GRB 251013C: AstroSat CZTI detection
- GRB 251011A: Swift/BAT-GUANO arcminute localization of a burst
- GRB 251013D: Swift/BAT-GUANO arcminute localization of a burst
- GRB 251013C: ALMA detection
- GRB 251013C: SVOM/COLIBRÍ (FM-GFT) detection of the optical counterpart
- GRB 251013C: DDOTI detection of the optical afterglow
- GRB 251013C: SLKT optical afterglow photometry
- Swift GRB 251014A: Global MASTER-Net observations report
- GRB 251014A: Swift detection of a possibly-short burst
- GRB 251014A: Fermi GBM Final Real-time Localization
- Fermi trigger No 782044789: Global MASTER-Net observations report
- Fermi GRB 251013C: Global MASTER-Net observations report
- Fermi GRB 251013B: Global MASTER-Net observations report
- Fermi GRB 251013D: Global MASTER-Net observations report
- GRB 251013C: Swift-XRT counterpart detection
- GRB 251013C: GOTO optical afterglow detection
- GRB 251013C: SAO RAS optical observations
- GRB 251013C: LCO optical afterglow detection
- GRB 251013C: Optical Observations via Virtual Telescope Project, Italy
- GRB 251013C: NOT spectroscopic redshift z = 0.572
- GRB 251013C: LAST detection of optical counterpart
- GRB 251013C: BOOTES-6 early optical detection
- GRB 251013D: Fermi GBM Final Real-time Localization
- GRB 251013C: SVOM/VT optical observation
- GRB 251013C: SVOM detection of a burst
- GRB 251013C: Fermi GBM Final Real-time Localization
- LIGO/Virgo/KAGRA S251013x: Updated Sky localization and Source Classification
- GRB 251013B: SVOM/GRM observation
- GRB 251013A: SVOM/GRM observation
- GRB 251003A: Mondy optical upper limit
- MASTER OT J011025.98-583210.6 : SVOM/VT optical observation
- GRB 251013B: Fermi GBM Final Real-time Localization
- Fermi GRB 251013A: Global MASTER-Net observations report
- GRB 251013A: Fermi GBM Final Real-time Localization
- LIGO/Virgo/KAGRA S251013x: Identification of a GW compact binary merger candidate
- GRB 251011B inspection: MASTER orphan GRB detection
- GRB 251011A: Insight-HXMT detection
- GRB 251011B: Swift/UVOT Upper Limits
- Fermi GRB 251011A: Global MASTER-Net observations report
- GRB 251012A: Fermi GBM Final Real-time Localization
- GRB 251011B: SVOM/GRM observation
- GRB 251011B: Swift-XRT refined Analysis
- GRB 251011B: Fermi GBM Observation
- GRB 251011B : MASTER optical observations
- GRB 251011C: Fermi GBM Final Real-time Localization
- GRB 251011B: Enhanced Swift-XRT position
- GRB 251010A: AstroSat CZTI detection
- GRB 251011A: AstroSat CZTI detection
- GRB 251009B: SVOM/GRM observation of short GRB
- GRB 251011B: Swift detection of a burst
- GRB 251011B: Fermi GBM Final Real-time Localization
- GRB 251011A: Fermi GBM Final Real-time Localization
- Fermi Gamma-ray Burst Monitor trigger 781824269/251010892 is not a GRB
- GRB 251007B: Swift/UVOT Upper Limits
- GRB 251010A: Fermi GBM Final Real-time Localization
- GRB251007A: Swift/UVOT Detection
- GRB 251009A: GECAM-B detection of a short burst
- GRB 251009A: Insight-HXMT detection of a short burst
- GRB 251009B (short): Glowbug gamma-ray detection
- GRB 251009B: Insight-HXMT detection of a short burst
- GRB 251007A: Swift-BAT refined analysis
- GRB 251009A: SVOM/GRM observation of short GRB with possible tail emission
- GRB 251007A: SVOM/GRM observation
- GRB 251007A: Insight-HXMT detection
- GRB 251006A: CALET Gamma-Ray Burst Monitor detection
- GRB 251007B - SVOM/ECLAIRs refined analysis
- SVOM/sb25101004: SVOM detection of a stellar flare
- GRB 251009A: Fermi GBM Final Localization
- GRB 250916A: TERI Gamma-ray detection
- GRB 250919A: TERI gamma-ray detection
- EP251006a: Global MASTER-Net observations report
- GRB 251006A: Fermi GBM Observation
- GRB 251007A: 1.5m OSN and 2.2m CAHA optical follow-up
- GRB 251002A - SVOM/ECLAIRs refined analysis
- IceCube alert 141456_888784 retraction
- IceCube Alert 251008A: Global MASTER-Net observations report
- GRB 251003A: Fermi GBM Observation
- GRB 251006B: Fermi GBM Observation
- GRB 251007B: COLIBRÍ optical upper limit
- GRB 251007A: AstroSat CZTI detection
- GRB 251006B/EP251006a: EP-FXT afterglow detection
- GRB 250917B: iTelescope T-26 upper limit
- EP250911a: Koshka Zeiss-1000 Optical Upper Limit
- GRB 251007B: SVOM/VT optical candidate
- GRB 251007A: Swift-XRT refined Analysis
- GRB 251007A: Enhanced Swift-XRT position
- GRB 251007B: Swift-XRT refined Analysis
- GRB 251007B: Enhanced Swift-XRT position
- GRB 251007A: NOT optical observations
- GRB 251007A: AKO Optical Upper Limit
- GRB 251007A: CALET Gamma-Ray Burst Monitor detection
- GRB 251006B: Insight-HXMT detection
- GRB 251007A: SVOM/C-GFT optical observations
- GRB 251005C: PRIME J-band upper limit
- Swift GRB 251007B: Global MASTER-Net observations report