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.
Advanced Search Examples (click to copy):
subject:"Swift"body:"GRB"submitter:"Judith Racusin"32492 results found.
- LIGO/Virgo/KAGRA S240422ed: Continued Imaging of Mag24a
- LIGO/Virgo/KAGRA S240422ed: Archival DECaPSs2 observations of the field of Mag24a
- LIGO/Virgo/KAGRA S240422ed: DECam GW-MMADS Candidates
- LIGO/Virgo/KAGRA S240422ed: Potential Magellan candidates from GCN 36263 are unrelated.
- LIGO/Virgo/KAGRA S240422ed: NOT J-band upper limit on the Swift/XRT source S240422ed_X61
- LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Three Potential Electromagnetic Counterparts Reported So Far
- GRB 240421B: GRBAlpha detection
- LIGO/Virgo/KAGRA S240422ed: Magellan Detection of a Potential Electromagnetic Counterpart
- LIGO/Virgo/KAGRA S240422ed: SAGUARO upper limits from CSS
- LIGO/Virgo/KAGRA S240422ed: Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
- LIGO/Virgo/KAGRA S240422ed: LAST optical observations
- LIGO/Virgo/KAGRA S240422ed: Potential Candidates from Magellan galaxy-based search
- LIGO/Virgo/KAGRA S240422ed: WINTER J-band upper limits on the Swift/XRT source S240422ed_X61
- IceCube-240419A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S240421ar: Updated Sky localization
- LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam upper limits on the Swift/XRT source S240422ed_X61
- LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from Pan-STARRS observations of the skymap
- LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search
- LIGO/Virgo/KAGRA S240422ed: No Counterparts in DDOTI/OAN Optical Observations
- GRB 240419A: Swift-BAT refined analysis
- GRB 240418A: Swift-BAT refined analysis
- LXT240402A/GRB240402B: Chandra X-ray detection
- LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS observations
- GRB 240419A: Possible ATCA radio detection
- GRB 240421B: ATCA radio observations
- LIGO/Virgo/KAGRA S240422ed: WINTER near-infrared J-band observations
- LIGO/Virgo S240422ed: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
- LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility observations and candidates
- LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam observations
- LIGO/Virgo/KAGRA S240422ed: Magellan Observations
- LIGO/Virgo/KAGRA S240422ed: Upper limits from Fermi-GBM Observations
- LIGO/Virgo/KAGRA S240422ed: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S240422ed: Coverage and upper limits from MAXI/GSC observations
- LIGO/Virgo/KAGRA S240422ed: MeerLICHT and BlackGEM observations report
- LIGO/Virgo/KAGRA S240422ed: Identification of a GW compact binary merger candidate
- GRB 240421A: Glowbug gamma-ray detection
- GRB 240414A: radio detection with the VLA
- Fermi-LAT gamma-ray observations of IceCube-240419A
- GRB 240414A: AMI-LA radio observations
- GRB 240414A: LBT optical detection
- GRB 240419B : MITSuME Akeno optical upper limits
- Fermi GRB 240422A: Global MASTER-Net observations report
- GRB 240421B: AstroSat CZTI detection
- Fermi GRB 240421B: Global MASTER-Net observations report
- Swift GRB 240421B: Global MASTER-Net observations report
- GRB 240421B: Fermi GBM Observation
- GRB 240421B: J-band upper limits from WINTER
- GRB 240421B: Swift/UVOT Upper Limits
- Fermi GRB 240421A: Global MASTER-Net observations report
- EP240417a: no counterpart detection by SOAR
- EP240420a: TNT upper limit to its optical counterpart
- EP240420a: Nanshan optical counterpart observations
- EP240420a: GWAC-F50A optical upper limit
- LIGO/Virgo/KAGRA S240421ar: Identification of a GW unmodeled transient candidate
- EP240420a: detection of fading X-ray emission with refined position by EP-FXT
- EP240420a: NOT optical counterpart candidate and potential host
- GRB240419A: Skynet Optical Afterglow Analysis
- GRB240418A - Candidate afterglow from NIRES
- GRB 240419B: Swift/UVOT Upper Limits
- GRB 240419A: Swift/UVOT Upper Limits
- GRB 240419B: optical afterglow from the NOT
- EP240414a: Near-IR observations with NIRES and WINTER
- Swift GRB 240419B: Global MASTER-Net observations report
- EP240414A: Terskol Zeiss-2000 optical upper limit
- Swift GRB 240419A: Global MASTER-Net observations report
- GRB 240418A: Swift/UVOT Upper Limits
- GRB 240419A: REM NIR afterglow detection
- GRB 240411B: Swift/UVOT Detection
- EP240417a: YAHPT Optical Upper Limits
- GRB240418A: YAHPT Upper Limits
- GRB 240419A: VLT/UVES redshift of z = 5.178
- GRB 240419A: VLT optical afterglow detection
- EP240416a: J-band observations with WINTER
- EP240414a: GMG observation
- GRB 240418A: TSHAO Zeiss-1000 optical upper limit
- GRB 240418A: NOT optical upper limits
- GRB 240418A: AKO Upper Limit
- GRB 240411A: GOTO early optical upper limits
- Fermi GRB 240417A: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S240413p: X-ray upper limits from EP-WXT for the candidate AGN counterpart
- EP240416A: Terskol Zeiss-2000 optical upper limit
- EP240416A: Khureltogoot optical upper limit
- Improved IPN triangulation of GRB 240411A
- EP240416a: BOOTES-2/TELMA Optical Upper Limit
- EP240414a: GSP detects optical candidate counterpart AT2024gsa
- LIGO/Virgo/KAGRA S240413p: DECam GW-MMADS candidates
- EP240414a: Pan-STARRS detects re-brightening of the candidate counterpart AT2024gsa
- LIGO/Virgo/KAGRA S240413p: historical ATLAS and ZTF observations of the candidate AGN counterpart
- GRB 240415A: Glowbug gamma-ray detection
- GRB 240414A: Glowbug gamma-ray detection
- LIGO/Virgo/KAGRA S240413p: STEP - T80S Search and Candidate Counterpart Identification
- GRB 240415B: GECAM-B detection
- EP 240416a: Xinglong and NOT decaying optical counterpart
- GRB 240415A: Swift-BAT refined analysis
- EP240416A: MASTER optical observations
- GRB 240411A: Glowbug gamma-ray detection
- GRB 240414A: Swift-BAT refined analysis
- EP240416a: Kinder optical counterpart candidate
- GRB 240414A: AbAO optical upprer limit
- GRB 240415A: Swift/UVOT Detection