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').
- GRB 240913A: Fermi GBM Final Real-time Localization
- GRB 240912A: J-band observations with WINTER
- GRB 240912A: Swift-XRT refined Analysis
- GRB 240912A: Fermi GBM Observation
- Swift GRB 240912A: Global MASTER-Net observations report
- GRB 240912A: LCOGT detection and Legacy Surveys likely host galaxy
- GRB 240911A: Tiled Swift observations
- Fermi Gamma-ray Burst Monitor trigger 747839931/240912555 is not a GRB
- GRB 240912A : INTEGRAL SPI ACS LIGHT CURVE
- GRB 240912B: Fermi GBM Final Real-time Localization
- GRB 240912A: NOT optical spectroscopy
- GRB 240912A: Enhanced Swift-XRT position
- GRB 240912A: Redshift from OSIRIS+/GTC
- Fast X-ray Transient EP240801a: GMRT radio observations
- GRB 240910A: Redshift from OSIRIS+/GTC
- GRB 240912A: Swift detection of a burst with an optical counterpart
- GRB 240912A: Fermi GBM Final Real-time Localization
- GRB 240910A: Fermi GBM Observation
- GRB 240910A: NOT optical observations
- GRB 240911A : a likely weak GRB detected by SVOM/ECLAIRs
- GRB 240910A: Swift-XRT detection of GOTO24fvl/AT2024vfp
- GRB 240910A: JinShan optical observations
- GRB 240910A: GOTO candidate optical counterpart
- EP240908a: Optical afterglow confirmation
- GRB 240710A: SVOM/GRM observation
- GRB 240910A: Swift ToO observations
- IPN triangulation of GRB 240905B (short)
- GRB 240825A: 7DT Optical Upper Limit
- GRB 240905E: SVOM/VT optical observations
- GRB 240905E: SVOM/VT optical observations (duplicate submission of GCN 37453)
- LIGO/Virgo/KAGRA S240910ci: NED Galaxies in the Localization Volume
- GRB 240910A: GRBAlpha detection
- GRB 240910B: Fermi GBM Final Real-time Localization
- LIGO/Virgo/KAGRA S240910ci: Coverage and upper limits from MAXI/GSC observations
- LIGO/Virgo/KAGRA S240910ci: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S240910ci: Identification of a GW compact binary merger candidate
- GRB 240910A: SVOM/GRM observation
- EP240908a: Mondy and AbAO follow-up observations
- EP240908a: Updates on the WXT detection result around the trigger time
- Fermi GRB 240910A: Global MASTER-Net observations report
- GRB 240910A: Fermi GBM Final Real-time Localization
- LIGO/Virgo/KAGRA S240908bs: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S240907cg: Upper limits from Swift/BAT-GUANO
- EP240908a: optical afterglow candidate
- EP EP240908a: Global MASTER-Net observations report
- GRB 240905B: Fermi GBM Observation
- Fermi trigger No 747553301: Global MASTER-Net observations report
- EP240908a: TRT optical upper limit
- GRB 240905B: GOTO optical upper limits
- EP240908a: EP detection of a fast X-ray transient
- Fermi GRB 240908A: Global MASTER-Net observations report
- 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