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.
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search
To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.
Lucene Examples (click to copy):
subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
19142 results found.
- GRB 250108B: Gemini-North likely redshift z = 2.197
- GRB 250108B: 1.3m DFOT upper limit
- GRB 250108B: REM optical/NIR upper limits
- EP250109a: SVOM/VT optical candidate
- EP250109a: Global MASTER-Net observations report
- GRB 250101A: Terskol K-800 optical observations
- EP250109a: GOTO optical upper limits
- GRB 250108A: Swift/UVOT Upper Limits
- EP250108a: Global MASTER-Net observations report
- EP250109a: EP-WXT detection of an X-ray transient
- GRB 250108A: NOT optical upper limit
- EP250108a: EP-WXT detection of an X-ray transient
- Swift GRB 250108B: Global MASTER-Net observations report
- 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
- GRB 250108B: Swift/UVOT Upper Limits
- GRB 250103A: Swift-XRT afterglow detection
- GRB 250108A: Swift ToO observations
- Fermi GRB 250107B: Global MASTER-Net observations report
- GRB 250107A: Swift ToO observations
- GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
- GRB 250106A: SVOM/VT 2nd optical deep observation
- 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: Swift-XRT observations
- GRB 250106A: SVOM/VT optical candidate
- GRB 250106A: Swift ToO observations
- GRB 250106A: SVOM detection of a long burst
- Fermi trigger No 757753930: Global MASTER-Net observations report
- GRB 241229A: SVOM/VT optical upperlimit
- 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
- 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
- Swift GRB 250103B: Global MASTER-Net observations report
- GRB 250103A: SVOM/VT optical counterpart confirmation
- GRB 250103A: Swift ToO observations
- GRB 250101a: Liverpool Telescope optical follow-up
- Fermi GRB 250102A: Global MASTER-Net observations report
- GRB 250103A: GOTO 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
- LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
- 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: 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
- Fermi GRB 250101B: Global MASTER-Net observations report
- GRB 250101A: SAO RAS observations of optical brightening
- GRB 250101A: SAO RAS optical observations
- GRB 250101A: SVOM/C-GFT early optical observations
- LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
- GRB 250101A: MASTER earlier OT observations with SOSS emission features
- GRB 250101A: Nanshan/HMT optical observations
- GRB 250101A : GIT optical detection
- Swift GRB250101.56: Global MASTER-Net observations report
- GRB 241217a/EP241217b: ATCA Radio Detection
- EP241217a: VLA Radio Detection
- LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
- GRB 241229B: Continued CrAO ZTSh observations
- LIGO/Virgo/KAGRA S241231bg: Updated NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S241231bg: NED Galaxies in the Localization Volume
- GRB 241229A: EP-FXT X-ray afterglow confirmation
- GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
- EP241217A: J band upper limit by SYSU 80cm telescope
- GRB 241228B: SAO RAS optical observations
- GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
- GRB 241229A: SAO RAS optical observations
- GRB 241229B: SVOM/VT optical candidate
- GRB 241229A: Swift-XRT observations
- EP240702a: 7DT Optical upper limits
- GRB 240606B: 7DT Optical upper limits
- Fermi trigger No 757231333: Global MASTER-Net observations report
- GRB241229B: UVOT upper limits
- GRB 241228B: D50 optical detection
- GRB 241228B: Fermi GBM Observation
- GRB 241228B: Swift-XRT afterglow detection
- GRB 241229A: Swift ToO observations
- GRB 241229B: NUTTelA-TAO / BSTI Optical Limits
- GRB 241228A: Mondy optical afterglow observations