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').
18802 results found.
- LIGO/Virgo/KAGRA S240422ed: Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
- 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
- LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from Pan-STARRS observations of the skymap
- LIGO/Virgo/KAGRA S240422ed: No Counterparts in DDOTI/OAN Optical Observations
- LXT240402A/GRB240402B: Chandra X-ray detection
- 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: 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: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S240422ed: Global MASTER-Net observations report
- GRB 240421A: Glowbug gamma-ray detection
- GRB 240414A: radio detection with the VLA
- GRB 240414A: AMI-LA radio observations
- GRB 240414A: LBT optical detection
- GRB 240419B : MITSuME Akeno optical upper limits
- GRB 240415B: Swift-XRT observations
- GRB240421B: Zadko Observations
- GRB 240421B: J-band upper limits from WINTER
- GRB 240421B: Swift/UVOT Upper Limits
- GRB 240421B: Enhanced Swift-XRT position
- EP240417a: no counterpart detection by SOAR
- EP240420a: TNT upper limit to its optical counterpart
- EP240420a: Xinglong decaying optical counterpart
- GRB 240421B: Swift detection of a burst
- 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
- EP240420a: EP-WXT detection of a fast X-ray transient
- GRB 240419A: Swift/UVOT Upper Limits
- GRB 240419B: Swift-XRT refined Analysis
- GRB 240419B: optical afterglow from the NOT
- GRB 240419B: Enhanced Swift-XRT position
- GRB 240418A: Swift/UVOT Upper Limits
- GRB 240419A: REM NIR afterglow detection
- GRB 240419A: Swift-XRT refined Analysis
- GRB 240419B: Swift detection of a burst
- GRB 240411B: Swift/UVOT Detection
- EP240417a: YAHPT Optical Upper Limits
- GRB 240419A: VLT optical afterglow detection
- GRB 240419A: Enhanced Swift-XRT position
- EP240416a: J-band observations with WINTER
- EP240414a: GMG observation
- GRB 240419A: Swift detection of a burst
- GRB 240418A: TSHAO Zeiss-1000 optical upper limit
- GRB 240418A: NOT optical upper limits
- GRB 240418A: Enhanced Swift-XRT position
- GRB 240418A: AKO Upper Limit
- GRB 240418A: Swift detection of a burst
- EP240417a: EP-WXT detection of a fast X-ray transient
- LIGO/Virgo/KAGRA S240413p: X-ray upper limits from EP-WXT for the candidate AGN counterpart
- Improved IPN triangulation of GRB 240411A
- EP240416a: BOOTES-2/TELMA Optical Upper Limit
- LIGO/Virgo/KAGRA S240413p: DECam GW-MMADS candidates
- 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
- EP 240416a: Xinglong and NOT decaying optical counterpart
- EP240416A: MASTER optical observations
- GRB 240411A: Glowbug gamma-ray detection
- EP240416a: Kinder optical counterpart candidate
- EP240416a: EP-WXT detection of a fast X-ray transient
- GRB 240414A: AbAO optical upprer limit
- GRB 240415A: Swift/UVOT Detection
- GRB 240414A: GAD Observatory, La Spezia, Italy ,upper limit
- GRB 240415A: Earliest optical followup with the Kinder observations
- GRB 240414A: GMG observation
- EP 240414a: BOOTES-4/MET Optical Upper Limits
- EP240414a: EP-FXT follow-up observation
- GRB 240415A: Enhanced Swift-XRT position
- GRB 240415A: OHP/T193 optical observations
- GRB 240415A: SAO RAS optical observations
- GRB 240415A: Mondy optical transient detection
- GRB 240414A: Photometric observation from 2.2m CAHA
- GRB 240414A: Swift/UVOT Detection
- LXT 240402A/GRB 240402B: Swift follow-up observations
- GRB 240414A: Mondy optical observations
- GRB 240414A: AKO Optical Upper Limit
- X-ray transient EP 240414a - GTC spectroscopic observations
- GRB 240415A: Prompt Swift-XRT observations
- EP240413a: Upper limits from GECAM-B Observation
- EP 240414a: NOT optical counterpart confirmation
- GRB240414A : J-band upper limits from WINTER
- GRB 240414A: Enhanced Swift-XRT position
- GRB 240414A: MarSEC Observatory, Vicenza, Italy, UPPER LIMIT
- LIGO/Virgo/KAGRA S240413p: No Counterparts in DDOTI/OAN Optical Observations
- EP240413A: GOTO optical upper limits
- GRB 240414A: Skynet Optical Afterglow Observations
- EP240414a: Kinder optical counterpart candidate possibly associated with the galaxy SDSS J124601.99-094309.3