GCN Circulars
GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"- Swift GRB250807.65: Global MASTER-Net observations report
- GRB 250807A: Enhanced Swift-XRT position
- IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250807B: Swift detection of a burst with an optical counterpart.
- GRB 250805A: Kilonova-Catcher optical upper limits
- EP250806a:SVOM/VT refined analysis
- GRB 250805A: Swift/UVOT Upper Limits
- GRB 250806A: Swift/UVOT U-band detection
- EP250806a: Liverpool telescope optical upper limit
- GRB 250807A: Swift detection of a burst with an optical counterpart
- IceCube Alert 250804.84: Global MASTER-Net observations report
- GRB 250806A: EP-FXT observation
- EP#01709198415/EP250806a: Swift-XRT observations
- EP250806a: Global MASTER-Net observations report
- EP250802a: EP-FXT follow-up observation
- EP250806a: refined analysis of the EP-WXT and EP-FXT observations
- EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
- EP250806a: SVOM /VT optical candidate
- GRB 250806A: J-band upper limit from WINTER
- GRB 250805A: Swift-BAT refined analysis
- GRB 250806A: KAIT optical upper limit
- GRB 250806A: SVOM/VT refined analysis
- GRB 250806A: Swift-XRT counterpart detection
- EP250806a: COLIBRÍ optical upper limit
- GRB 250806A: Kilonova-Catcher optical upper limits
- EP250806a: Einstein Probe detection of an X-ray transient
- GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250806A: SVOM/VT optical upper limit
- GRB 250806A: SVOM detection of a soft burst
- GRB 250805A: SVOM/VT optical counterpart
- GRB 250805A: ESO/VLT observations
- GRB 250805A: Swift-XRT refined Analysis
- GRB 250804B: Swift-XRT observations
- GRB 250805A: Enhanced Swift-XRT position
- GRB 250804C: AstroSat CZTI detection of a long burst
- GRB 250805A: TRT optical upper limits
- IceCube-250804A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 250805A: Swift-XRT observations
- GRB 250805A: Swift detection of a burst
- Swift GRB250805.26: Global MASTER-Net observations report
- GRB 250804B: Tiled Swift observations
- Fermi trigger No 776041355: Global MASTER-Net observations report
- GRB 250804B: SVOM/GRM observation of a short burst
- GRB 250804A: Fermi GBM Final Localization
- EP250802a: additional Liverpool Telescope upper limits
- EP250730a: SVOM/VT optical upper limit
- Fermi Gamma-ray Burst Monitor trigger 775945985/250803856 is not a GRB
- EP250802a: Liverpool Telescope optical upper limits
- EP250802a: Global MASTER-Net observations report
- EP250802a: GROWTH-India Telescope optical upper limit
- EP250802a: Einstein Probe detection of an X-ray transient
- LIGO/Virgo/KAGRA S250802dn: Updated Sky localization
- The EP-WXT trigger 01709198251 is likely a flaring star
- LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
- The EP-WXT trigger 01709198202 is likely a flaring star
- LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
- GRB 250702B: SMA observations
- LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
- LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
- EP250711a: CrAO and Assy optical observations
- LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
- EP250730a: Global MASTER-Net observations report
- EP250730a: COLIBRÍ optical upper limit
- GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
- EP250730a: Einstein Probe detection of an X-ray transient
- LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
- LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
- LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
- GRB 250725A: AstroSat CZTI detection
- GRB 250727A: EP-FXT follow-up observation
- GRB 250725A: PRIME near-infrared observations
- LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
- LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
- GRB: Clarification on Gamma-Ray Burst Naming Convention
- GRB 250728A: Swift-XRT observations
- GRB 250727A: SVOM/ECLAIRs refined analysis
- EP-WXT trigger 01709195487: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
- GRB 250728A: COLIBRÍ optical upper limit
- GRB 250728A: Fermi GBM Observation
- Fermi trigger No 775387550: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250727dc: Updated Sky localization
- LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
- GRB 250728A: Swift ToO observations
- GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
- GRB 250727A: AST3-2 Upper limit
- LIGO/Virgo/KAGRA S250727cl: Updated Sky localization
- GRB 250727A: EP-FXT counterpart detection
- GRB250727A: SVOM/VT optical upper limit
- GRB 250727A: Swift-XRT observations
- LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
- GRB 250727A: SVOM detection of a burst
- LIGO/Virgo/KAGRA S250725l: Updated Sky localization
- LIGO/Virgo/KAGRA S250726ak: Updated Sky localization
- The EP-WXT trigger 01709195487 is likely a flaring star
- Swift detection of the Soft Gamma Repeater PSR J1647-4552