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').
- LIGO/Virgo/KAGRA S240908dg: Updated Sky localization
- LIGO/Virgo/KAGRA S240908bs: Updated Sky localization
- GRB 240908A: Fermi GBM Final Real-time Localization
- LIGO/Virgo/KAGRA S240908dg: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S240908bs: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S240907cg: Updated Sky localization
- GRB 240801A: SVOM/GRM observation
- LIGO/Virgo/KAGRA S240907cg: Identification of a GW compact binary merger candidate
- GRB 240905E: GIT optical upper limit
- GRB 240905B: Swift-XRT observations
- GRB 240905E: Gaoyazi/GOT optical upper limits
- GRB 240905E: NUTTelA-TAO / BSTI Optical Limits
- GRB 240905B: Fermi-LAT detection
- GRB 240905B: Swift ToO observations
- GRB 240905E: J-band observations with WINTER
- GRB 240905E: CrAO Optical Afterglow observations, possible OT candidate
- GRB 240905E: AKO Optical Upper Limit
- GRB 240905E: SVOM/C-GFT optical upper limit
- GRB 240905E: OHP/MISTRAL T193 optical upper limit
- Fermi GRB 240905D: Global MASTER-Net observations report
- Fermi GRB 240905A: Global MASTER-Net observations report
- GRB 240905E: NOT optical upper limits
- GRB 240905E: REM optical/NIR upper limits
- GRB 240902B: AstroSat CZTI detection of a long burst
- GRB 240905E: Swift-XRT refined Analysis
- GRB 240902A: AstroSat CZTI detection of a long burst
- GRB 240905E: SVOM/GRM observation
- GRB 240905E: LCOGT Optical Upper Limit
- GRB 240905E: Swift/UVOT Upper Limits
- GRB 240905E: SAO RAS optical upper limit
- GRB 240825A: Montarrenti Observatory optical follow-up observations
- GRB 240905E: Nanshan/HMT optical upper limit
- Swift GRB 240905E: Global MASTER-Net observations report
- GRB 240905E: Swift detection of a burst
- GRB 240819A: Optical upper limits from TESS
- GRB 240905D: AstroSat CZTI detection
- GRB 240905A: SVOM/GRM observation
- Fermi GRB 240905B: Global MASTER-Net observations report
- GRB 240905D: Fermi GBM Final Real-time Localization
- GRB 240905B: AstroSat CZTI detection and localization
- GRB 240905C: Fermi GBM Final Real-time Localization
- GRB 240905B: Fermi GBM Final Real-time Localization
- GRB 240825A: ATCA Detection of Radio Counterpart
- Swift GRB 240904A: Global MASTER-Net observations report
- GRB 240905A: Fermi GBM Final Real-time Localization
- Fermi Gamma-ray Burst Monitor trigger 747163821/240904729 is not a GRB
- Fermi trigger No 747163821: Global MASTER-Net observations report
- GRB 240904A: Swift detection of a burst
- GRB 240828A: SVOM/GRM observation
- LIGO/Virgo/KAGRA S240825ar: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S240807h: Upper limits from Swift/BAT-GUANO
- Fermi Gamma-ray Burst Monitor trigger 240831A is not a GRB
- LIGO/Virgo/KAGRA S240902bq: Updated Sky localization
- GRB 240828A: GECAM detection
- GRB 240831B: Fermi GBM Final Localization
- Fermi Gamma-ray Burst Monitor trigger 746882332/240901471 is not a GRB
- LIGO/Virgo/KAGRA S240902bq: Identification of a GW compact binary merger candidate
- GRB 240825A: Magnitude Correction in SVOM/C-GFT Optical Observations
- GRB 240825A: MeerLICHT afterglow detection
- Fermi trigger No 746923430: Global MASTER-Net observations report
- GRB 240828A: SAO RAS AS-500(2) optical observations
- GRB 240821A: VLT spectroscopic observations
- Fermi trigger No 746882332: Global MASTER-Net observations report
- GRB 240825A: TSHAO Optical Upper Limit
- GRB 240829B: GRBAlpha detection
- GRB240828B: REM optical/NIR upper limits
- Fermi trigger No 746816563: Global MASTER-Net observations report
- GRB 240828B: AbAO optical upper limit
- GRB 240831A: Fermi GBM Final Real-time Localization
- GRB 240825A: SOAR observations
- GRB 240828B: Mephisto optical upper limit
- GRB 240828B: GRANDMA Optical Upper Limit
- LIGO/Virgo/KAGRA S240830gn: Coverage and upper limits from MAXI/GSC observations
- LIGO/Virgo/KAGRA S240830gn: Updated Sky localization and EM Bright Classification
- GRB 240829A: Swift-BAT refined analysis
- GRB 240825A: Swift-BAT refined analysis
- LIGO/Virgo/KAGRA S240830gn: Identification of a GW compact binary merger candidate
- GRB 240825A: MeerKAT detection
- GRB 240828B: J-band upper limit from WINTER
- Fermi trigger No 746684112: Global MASTER-Net observations report
- GRB 240828B: GMG Optical Upper Limit
- GRB 240828A: KAIT continued optical observations
- GRB 240828B: GWAC-F50A optical upper limit
- GRB 240828B: SVOM/C-GFT optical upper limit
- GRB 240828B: SAO RAS optical upper limit
- GRB 240828B: KAIT optical upper limit
- GRB 240828A: SAO RAS optical observations
- Fermi trigger No 746587425: Global MASTER-Net observations report
- GRB 240829B: Fermi GBM Final Localization
- GRB 240828A: Fermi GBM Observation
- GRB 240629A: First GRB Detected by BurstCube
- GRB 240828A: KAIT Optical Afterglow Candidate
- GRB 240825A: SVOM/VT optical detection
- GRB 240828A: Swift-XRT afterglow detection
- GRB 240825A: further SAO RAS optical observations
- GRB 240825A: iTelescope optical observations
- GRB 240828B: Swift-XRT afterglow detection
- GRB 240829A: Swift detection of a burst
- Swift GRB240829.16: Global MASTER-Net observations report
- GRB 240828A: Fermi-LAT detection