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 250101A: Terskol K-800 optical observations
- EP250109a: GOTO optical upper limits
- EP250109a: Swift/XRT non-detection
- GRB 250108A: Swift/UVOT Upper Limits
- EP250108a: Global MASTER-Net observations report
- EP250109a: EP-WXT detection of an X-ray transient
- 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 250108B: Swift-XRT refined Analysis
- Swift GRB 250108B: Global MASTER-Net observations report
- Fermi Gamma-ray Burst Monitor trigger 758061038/250108855 is not a GRB
- LIGO/Virgo/KAGRA S250108ha: Retraction of GW compact binary merger candidate
- GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
- GRB 250103A: 1.6m Mephisto optical observations
- GRB 250108A: Swift-XRT afterglow detection
- GRB 250108A:SVOM/VT optical candidate
- 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: Swift ToO observations
- GRB 250108A: SVOM detection of a soft long burst
- GRB 250107A: Fermi GBM Observation
- GRB 241228B: Fermi-LAT detection
- Fermi GRB 250107B: Global MASTER-Net observations report
- GRB 250107A: Swift ToO observations
- GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
- GRB 250107B: Fermi GBM Final Real-time Localization
- GRB 250106A: SVOM/VT 2nd optical deep observation
- GRB 250101A: J band upper limit by SYSU 80cm telescope
- GRB 250107A: Fermi GBM Final Real-time Localization
- EPWXT01709129925: Xinglong optical observations
- GRB 250106A: NOT optical observations
- LIGO/Virgo/KAGRA S250104v: Updated Sky localization
- GRB 250103B: REM optical/NIR upper limits
- GRB 250101A: REM optical/NIR counterpart detection
- GRB 250106A: Swift-XRT observations
- GRB 250106A: SVOM/VT optical candidate
- GRB 250106A: Swift ToO observations
- The EP-WXT trigger 01709129925 is likely a flaring star
- GRB 250106A: SVOM detection of a long burst
- Fermi trigger No 757753930: Global MASTER-Net observations report
- GRB 241229A: SVOM/VT optical upperlimit
- GRB 250103B: Swift-XRT refined Analysis
- GRB 250103B: LCO/1m optical afterglow candidate detection
- GRB 250103A: Bassano Bresciano Observatory upper limit
- GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
- GRB 250103A: Swift-XRT observations
- 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
- GRB 250103A: NOT spectroscopic redshift
- GRB 250103B：SVOM/VT optical counterpart
- 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: Redshift 4.01 from OSIRIS+/GTC
- GRB 250103A: NOT optical observations
- GRB 250103A: TSHAO optical upper limit
- GRB 250103A: Fermi GBM Observation
- GRB 250103B: LCOGT Optical Upper Limit
- IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
- Swift GRB 250103B: Global MASTER-Net observations report
- GRB 250103A: SVOM/VT optical counterpart confirmation
- EP250101a: Liverpool Telescope optical upper limit
- GRB 250103A: Swift ToO observations
- IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
- 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
- Fermi GRB 250102A: Global MASTER-Net observations report
- 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
- IceCube Alert 250102.58: Global MASTER-Net observations report
- 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
- GRB 250102A: Fermi GBM Final Real-time Localization
- LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
- GRB 250101A: Swift-BAT refined analysis
- IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 250101A: further SAO RAS optical observations
- GRB 250101A: LCO optical counterpart detection
- EP241231b and EP250101a: EP-WXT detection of two X-ray transients
- GRB 250101A NUTTelA-TAO / BSTI Early Measurements
- GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
- GRB 250101A: Swift/UVOT Detection
- GRB 250101A: 1.6m Mephisto multi-band optical followup
- GRB 250101A: Swift-XRT refined Analysis
- Fermi Gamma-ray Burst Monitor trigger 757464861/250101954 is not a GRB
- GRB 250101A: Montarrenti Observatory optical observations and rebrightening
- IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event