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').
19115 results found.
- EP250109a: Swift/XRT non-detection
- GRB 250108A: Swift/UVOT Upper Limits
- LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
- GRB 250108A: NOT optical upper limit
- EP250108a: EP-WXT detection of an X-ray transient
- LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
- GRB 250103A: 1.6m Mephisto optical observations
- GRB 250108A: Swift-XRT afterglow detection
- LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
- GRB 250108B: Swift/UVOT Upper Limits
- GRB 250103A: Swift-XRT afterglow detection
- GRB 250108B: Enhanced Swift-XRT position
- GRB 250108B: Swift detection of a burst
- GRB 250108A: SVOM detection of a soft long burst
- GRB 241228B: Fermi-LAT detection
- GRB 250101A: J band upper limit by SYSU 80cm telescope
- EPWXT01709129925: Xinglong optical observations
- GRB 250106A: NOT optical observations
- GRB 250103B: REM optical/NIR upper limits
- GRB 250101A: REM optical/NIR counterpart detection
- GRB 250106A: SVOM detection of a long burst
- GRB 250103B: Swift-XRT refined Analysis
- GRB 250103B: LCO/1m optical afterglow candidate detection
- GRB 250103A: Bassano Bresciano Observatory upper limit
- GRB 250101A: 1.3m DFOT optical afterglow detection
- GRB 241229A: 1.3m DFOT upper limit
- GRB 241228B: 1.3m DFOT Optical observations
- GRB 241228A: 1.3m DFOT upper limit
- LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
- GRB 250103A: Montarrenti Observatory optical detection
- GRB 250101A: further LCOGT optical afterglow observations
- GRB 250103A: TSHAO optical upper limit
- GRB 250103A: Fermi GBM Observation
- GRB 250103B: LCOGT Optical Upper Limit
- EP250101a: Liverpool Telescope optical upper limit
- GRB 250101a: Liverpool Telescope optical follow-up
- GRB 250103B: SVOM detection of a long burst
- GRB 250103B: Swift detection of a burst
- GRB 250103A: Xinglong 2.16m Optical Candidate
- GRB 250101B: SVOM/GRM observation
- GRB 250103A: GOTO optical upper limit
- GRB 250103A: SVOM/C-GFT optical upper limit
- GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
- EP241231b: optical upper limit with the Liverpool Telescope
- GRB 250103A: SVOM detection of a long burst (duplicate submission)
- GRB 250103A: SVOM detection of a long burst
- EP250101a: Xinglong optical upper limit
- LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
- GRB 250101A: further SAO RAS optical observations
- GRB 250101A: LCO optical counterpart detection
- GRB 250101A NUTTelA-TAO / BSTI Early Measurements
- GRB 250101A: Swift/UVOT Detection
- GRB 250101A: 1.6m Mephisto multi-band optical followup
- GRB 250101A: Montarrenti Observatory optical observations and rebrightening
- GRB 250101A: LCOGT optical afterglow detection
- GRB 250101A: OASDG optical observations
- GRB 250101A: BOOTES-4/MET optical afterglow detection
- GRB 250101A: AKO Optical Afterglow Detection
- GRB 250101A: SAO RAS optical observations
- GRB 250101A: Enhanced Swift-XRT position
- GRB 250101A: SVOM/C-GFT early optical observations
- GRB 250101A : GIT optical detection
- GRB 250101A: GMG Optical Observation
- GRB 250101A: Swift detection of a burst with an optical counterpart
- LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
- LIGO/Virgo/KAGRA S250101k: Identification of a GW compact binary merger candidate
- GRB 241229B: Continued CrAO ZTSh observations
- LIGO/Virgo/KAGRA S241231bg: Updated Sky localization and EM Bright Classification
- GRB 241229A: EP-FXT X-ray afterglow confirmation
- GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
- GRB 241229B: SVOM/GRM observation
- LIGO/Virgo/KAGRA S241231bg: Identification of a GW compact binary merger candidate
- EP241217A: J band upper limit by SYSU 80cm telescope
- LIGO/Virgo/KAGRA S241230ev: Identification of a GW compact binary merger candidate
- GRB 241229B: SAO RAS optical upper limit
- GRB 241228B: SAO RAS optical observations
- GRB 241229A: SAO RAS optical observations
- Konus-Wind detection of GRB 241228A
- EP240702a: 7DT Optical upper limits
- GRB 240606B: 7DT Optical upper limits
- LIGO/Virgo/KAGRA S241230bd: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241225c: Updated Sky localization and EM Bright Classification
- GRB241229B: UVOT upper limits
- GRB 241228B: Swift-XRT afterglow detection
- GRB 241229B: Fermi GBM Observation
- GRB 241229B: NUTTelA-TAO / BSTI Optical Limits
- GRB 241228A: Mondy optical afterglow observations
- GRB 241229A: GOTO optical upper limits
- GRB 241228B: VLT/X-shooter redshift of z = 2.674
- GRB 241228A: NOT optical upper limits
- GRB 241228B: LCO optical observation
- GRB 241228A: Swift-BAT refined analysis
- GRB 241228B: Swift/BAT-GUANO localization skymap of a burst
- GRB241228B: GROWTH-India Telescope optical observations
- GRB 241226A: Swift/BAT-GUANO localization skymap of a burst
- GRB 241228A: GROWTH-India telescope optical upper limit
- GRB 241228B: TRT optical counterpart confirmation
- GRB 241228A: Swift/UVOT Upper Limits
- GRB 241228B: GOTO possible optical counterpart candidate
- GRB 241228A: Enhanced Swift-XRT position