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').
18292 results found.
- GRB 241002C: Swift-XRT observations confirm the source to be EI Eri
- GRB 241002C: Swift ToO observations
- IPN triangulation of GRB 240930B / EP 240930a
- GRB 240930B: CALET Gamma-Ray Burst Monitor detection
- GRB 241002A: Swift/UVOT Upper Limits
- GRB 241002A: Swift-XRT refined Analysis
- GRB 241002A: LCOGT Optical Upper Limits
- GRB 241001A: GRANDMA and Kilonova-Catcher optical afterglow detection and upper limits
- GRB 241001A: Swift/UVOT Detection
- GRB 241001A: Swift-XRT observations
- GRB241001A: optical afterglow candidate
- GRB 241002A: 1.5m OSN optical upper limit
- GRB 241002A: Enhanced Swift-XRT position
- GRB 241002A: Swift detection of a burst
- GRB 240930B: Fermi GBM Observation
- GRB 241001A: Swift ToO observations
- GRB 240930B: Swift/BAT-GUANO localization skymap of a burst
- SVOM/GRM detection of a burst from SGR Swift J1818.0-1607
- AMON NuEM 240926A: Swift XRT Follow-up
- Konus-Wind detection of GRB 240912A
- Swift Trigger 1256950 is probably not a GRB
- LIGO/Virgo/KAGRA S240921cw: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S240920dw: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S240919bn: Upper limits from Swift/BAT-GUANO
- GRB 240529A: FRAM-ORM early optical afterglow observations reveal plateau and rebrightening
- GW S240915b and S240919bn : Swift UVOT follow-up
- Insight-HXMT ToO observations of X-ray bursts from SGR 1E 1841-045 / Kes 73
- GRB 240716A: Swift/BAT-GUANO localization skymap of a long burst
- LIGO/Virgo S240919bn: GOTO optical upper limits
- LIGO/Virgo S240919bn: Swift XRT observations, 10 X-ray sources
- EP240913A/GRB 240913C: AbAO optical upper limit
- GRB 240910A: further Swift observations and confirmation of afterglow
- EP240918a: Swift-XRT observation
- GRB 240912A: Swift-BAT refined analysis
- IPN triangulation of GRB 240913C / EP 240913a
- GRB 240916A: Fermi GBM Observation
- GRB 240916A: Swift-XRT afterglow detection
- GRB 240916A: Swift ToO observations
- LIGO/Virgo S240915b: Swift XRT observations, 8 X-ray sources
- EP240913a/GRB 240913C: KAIT optical upper limit
- GRB 240914A: Swift-XRT observations
- GRB 240914A: Swift ToO observations
- EP240913a: ESO-NTT optical observations
- EP240913a: Swift/XRT detection of an X-ray source within the EP/WXT error circle
- GRB 240905E: further NOT optical observations
- EP240913a: EP-WXT detection of a fast X-ray transient
- GRB 240911A: LCO optical observations
- GRB 240911A: JinShan optical upper limits on two Swift/XRT candidates
- GRB 240912A: Swift/UVOT Detection
- GRB 240911A: GOTO optical limits on Swift/XRT candidates
- GRB 240912A: SVOM/GRM observation
- GRB 240911A: Swift-XRT observations
- 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
- GRB 240912A: NOT optical spectroscopy
- GRB 240912A: Enhanced Swift-XRT position
- GRB 240912A: Swift detection of a burst with an optical counterpart
- GRB 240910A: Fermi GBM Observation
- GRB 240910A: Swift-XRT detection of GOTO24fvl/AT2024vfp
- GRB 240910A: JinShan optical observations
- GRB 240910A: GOTO candidate optical counterpart
- GRB 240910A: Swift ToO observations
- IPN triangulation of GRB 240905B (short)
- GRB 240905E: SVOM/VT optical observations
- LIGO/Virgo/KAGRA S240908bs: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S240907cg: Upper limits from Swift/BAT-GUANO
- GRB 240905B: GOTO optical upper limits
- GRB 240905E: GIT optical upper limit
- GRB 240905B: Swift-XRT observations
- GRB 240905E: Gaoyazi/GOT optical upper 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: NOT optical upper limits
- GRB 240905E: REM optical/NIR upper limits
- GRB 240905E: Swift-XRT refined Analysis
- 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 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
- Swift GRB 240904A: Global MASTER-Net observations report
- GRB 240904A: Swift detection of a burst
- LIGO/Virgo/KAGRA S240825ar: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S240807h: Upper limits from Swift/BAT-GUANO
- GRB 240828A: GECAM detection
- GRB 240825A: MeerLICHT afterglow detection
- GRB240828B: REM optical/NIR upper limits
- GRB 240828B: AbAO optical upper limit
- GRB 240828B: Mephisto optical upper limit