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"38336 results found.
- GRB 250725A: AstroSat CZTI detection
- GRB 250727A: EP-FXT follow-up observation
- GRB 250725A: PRIME near-infrared observations
- 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
- GRB 250728A: COLIBRÍ optical upper limit
- GRB 250728A: Fermi GBM Observation
- Fermi trigger No 775387550: Global MASTER-Net observations report
- GRB 250728A: Swift ToO observations
- GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
- GRB 250727A: AST3-2 Upper limit
- GRB 250727A: EP-FXT counterpart detection
- GRB250727A: SVOM/VT optical upper limit
- GRB 250727A: Swift-XRT observations
- GRB 250727A: SVOM detection of a burst
- Swift detection of the Soft Gamma Repeater PSR J1647-4552
- GRB 250725A: Swift-XRT refined Analysis
- GRB 250725A: Fermi GBM Observation
- GRB 250725A: Swift-BAT refined analysis
- Konus-Wind detection of GRB 250725A
- GRB 250725A: SVOM/GRM observation
- GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
- GRB 250725A: Swift/UVOT Upper Limits
- GRB 250725A: Fermi-LAT detection
- GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
- GRB 250725A: BOOTES-7 early optical detection
- GRB 250725A: SVOM/VT optical candidate
- GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
- GRB 250725A: Enhanced Swift-XRT position
- GRB 250725A: Swift detection of a burst
- Swift GRB 250725A: Global MASTER-Net OT detection
- GRB 250725A: Fermi GBM Final Real-time Localization
- Fermi GRB 250725A: Global MASTER-Net observations report
- Swift GRB 250725A: Global MASTER-Net observations report
- GRB 250723B: Fermi GBM Final Real-time Localization
- GRB 250721A: Fermi GBM Observation
- GRB 250723A: Fermi GBM Final Real-time Localization
- Swift-BAT trigger 1334535 is not a GRB
- GRB 250721A: Swift-XRT observations
- GRB 250722A: Fermi GBM Final Real-time Localization
- GRB 250713A : SVOM/ECLAIRs refined analysis
- GRB 250717B: SVOM/GRM observation
- The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
- GRB 250721A: Tiled Swift observations
- GRB 250721A: MAXI/GSC detection
- GRB 250721A: Fermi GBM Final Localization
- GRB 250720B: Fermi GBM Final Localization Correction
- GRB 250720A: Fermi GBM Final Localization
- Fermi trigger No 774730635: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
- Fermi Gamma-ray Burst Monitor trigger 774670514/250720094 is not a GRB
- GRB 250717B: COLIBRÍ optical upper limit
- LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
- GRB 250717B: Swift-XRT observations
- GRB 250718B: Fermi GBM Final Localization Correction
- GRB 250718B: Fermi GBM Final Real-time Localization
- Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
- Swift Trigger 1334535: a possible GRB 250718A
- Swift GRB250718.01: Global MASTER-Net observations report
- GRB 250717B: Swift ToO observations
- GRB 270713A: Kitab and AbAO Optical Observations
- GRB 250717B: Fermi GBM Observation
- GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
- Konus-Wind detection of GRB 250716A
- GRB 250716A: Swift-XRT afterglow detection
- GRB 250717B: Fermi GBM Final Real-time Localization
- GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
- GRB 250717A: Fermi GBM Final Real-time Localization
- GRB 250716A: Swift ToO observations
- GRB 250716A: GOTO tentative optical counterpart candidate
- GRB 250716A: Fermi GBM Observation
- GRB 250714A: SVOM/GRM observation
- Fermi GRB 250716A: Global MASTER-Net observations report
- GRB 250716A: Fermi GBM Final Real-time Localization
- Fermi GRB 250715A: Global MASTER-Net observations report
- GRB 250715A: Fermi GBM Final Real-time Localization
- EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
- GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
- GRB 250713A: Mephisto optical upper limits
- Fermi GRB 250714A: Global MASTER-Net observations report
- GRB 250713A: SVOM/VT optical upper limit
- GRB 250713A: NOT optical upper limits
- GRB 250713A: OHP/T193 upper limit
- GRB 250713A: SVOM/C-GFT upper limit
- GRB 250714A: Fermi GBM Final Real-time Localization
- GRB 250706B/C: 7DT Follow-up Observations
- GRB 250713A: Swift-XRT observations
- GRB 250713A: EP-FXT counterpart detection
- EP250711a: COLIBRÍ continuous optical observations
- GRB 250706A: Swift-BAT refined analysis
- GRB 250702F: Swift-BAT refined analysis
- GRB 250628A: Swift-BAT refined analysis
- GRB 250713A: JinShan optical upper limits
- GRB 250713A: SVOM detection of a long burst
- EP250711a: Global MASTER-Net observations report
- GRB 250711A: DDOTI Optical Upper Limit
- EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
- GRB 250711A: SVOM/GRM observation