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"16161 results found.
- LIGO/Virgo/KAGRA S240422ed: Archival radio detection of EP240426a
- LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfq, AT2024hfr, AT2024hfs, and AT2024hfx
- LIGO/Virgo/KAGRA S240422ed: BOOTES-6/DPRT optical upper limits for EP240426a
- LIGO/Virgo/KAGRA S240422ed: GRANDMA Optical Upper Limits for EP240426a
- LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
- EP240426a: YAHPT optical upper limit
- LIGO/Virgo/KAGRA S240422ed: BOOTES-4/MET Optical Upper Limits for EP240426a
- LIGO/Virgo/KAGRA S240422ed: EP-FXT Detection of the Potential Opitcal Electromagnetic Counterpart AT 2024hfq Reported by DECam
- LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
- LIGO/Virgo/KAGRA S240422ed: Continued Magellan Observations
- EP240426a: GMG optical upper limit
- LIGO/Virgo/KAGRA S240422ed: Magellan Follow-up Observations of Swift/XRT candidates
- LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility contuinued observations of S240422ed and candidate analysis
- LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search update and AT2024hfx, AT2024hgl observations
- LIGO/Virgo/KAGRA S240422ed: Second night Pan-STARRS observations of the skymap
- LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA and Kilonova-Catcher galaxy targeting observations
- LIGO/Virgo/KAGRA S240422ed: ANU 2.3m followup of candidate counterparts
- LIGO/Virgo/KAGRA S240422ed: Magellan Spectrum of GW-MMADS Candidate AT2024hdo Indicates a Type II SN
- LIGO/Virgo/KAGRA S240413p: DESGW DECam Follow-Up
- LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
- LIGO/Virgo/KAGRA S240422ed: MOSFIRE spectroscopy of the DECam GW-MMADS candidate AT 2024hdn
- LIGO/Virgo/KAGRA S240422ed: ATCA follow-up of candidate counterparts
- LIGO/Virgo/KAGRA S240422ed: MOSFIRE imaging of the DECam GW-MMADS candidate AT 2024hdm
- LIGO/Virgo/KAGRA S240422ed: J-band non-detection of Mag24a
- LIGO/Virgo/KAGRA S240422ed: Continued Imaging of Mag24a
- LIGO/Virgo/KAGRA S240422ed: DECam GW-MMADS Candidates
- LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Three Potential Electromagnetic Counterparts Reported So Far
- LIGO/Virgo/KAGRA S240422ed: Magellan Detection of a Potential Electromagnetic Counterpart
- LIGO/Virgo/KAGRA S240422ed: LAST optical observations
- LIGO/Virgo/KAGRA S240422ed: Potential Candidates from Magellan galaxy-based search
- LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam upper limits on the Swift/XRT source S240422ed_X61
- LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search
- LIGO/Virgo/KAGRA S240422ed: No Counterparts in DDOTI/OAN Optical Observations
- LXT240402A/GRB240402B: Chandra X-ray detection
- LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS observations
- LIGO/Virgo/KAGRA S240422ed: Magellan Observations
- GRB 240414A: LBT optical detection
- GRB 240419B : MITSuME Akeno optical upper limits
- GRB240421B: BOOTES-5/JGT optical upper limit
- GRB 240421B: Swift/UVOT Upper Limits
- EP240417a: no counterpart detection by SOAR
- EP240420a: TNT upper limit to its optical counterpart
- EP240420a: Xinglong decaying optical counterpart
- EP240420a: Nanshan optical counterpart observations
- EP240420a: GWAC-F50A optical upper limit
- 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
- EP240414A: Terskol Zeiss-2000 optical upper limit
- GRB 240418A: Swift/UVOT Upper Limits
- GRB 240419A: REM NIR afterglow detection
- GRB 240411B: Swift/UVOT Detection
- EP240417a: YAHPT Optical 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 240411A: GOTO early optical upper limits
- 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
- EP240416a: BOOTES-2/TELMA Optical Upper Limit
- EP240414a: GSP detects optical candidate counterpart AT2024gsa
- 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
- LIGO/Virgo/KAGRA S240413p: STEP - T80S Search and Candidate Counterpart Identification
- EP 240416a: Xinglong and NOT decaying optical counterpart
- EP240416A: MASTER optical observations
- EP240416a: Kinder optical counterpart candidate
- GRB 240414A: AbAO optical upprer limit
- GRB 240415A: Swift/UVOT Detection
- EP240413a: BOOTES-2/TELMA Optical Upper Limit
- GRB 240414A: GAD Observatory, La Spezia, Italy ,upper limit
- GRB 240415A: Earliest optical followup with the Kinder observations
- EP 240414a: BOOTES-4/MET Optical Upper Limits
- EP240414a: EP-FXT follow-up observation
- GRB 240415A: OHP/T193 optical observations
- GRB 240415A: optical afterglow detection from the INAF Asiago Observatory
- GRB 240415A: SAO RAS optical observations
- GRB 240415A: Mondy optical transient detection (photometry correction in GCN 36118 )
- 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
- EP 240414a: NOT optical counterpart confirmation
- GRB240414A : J-band upper limits from WINTER
- GRB 240414A : OHP/T193 second epoch of optical follow-up and afterglow detection
- 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