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').
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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"7420 results found.
- LIGO/Virgo/KAGRA S240505av: Upper limits from Swift/BAT-GUANO
- GRB 240513A: Tiled Swift observations
- LIGO/Virgo/KAGRA S240513ei: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S240513cx: Coverage and upper limits from MAXI/GSC observations
- LIGO/Virgo/KAGRA S240512r: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S240512r: Identification of a GW compact binary merger candidate
- GRB 240511A: Swift detection of a burst
- LIGO/Virgo/KAGRA S240511i: Updated Sky localization
- LIGO/Virgo/KAGRA S240511i: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S240422ed: P200 observations of AT2024hit
- LIGO/Virgo/KAGRA S240422ed: Candidates from the latest GW-MMADS DECam Observations
- LIGO/Virgo/KAGRA S240507p: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S240422ed: Upper limits from a two-week IceCube neutrino search
- LIGO/Virgo/KAGRA S240507p: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S240422ed: Additional WINTER near-infrared J-band observations
- LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfr and AT2024hfs
- LIGO/Virgo/KAGRA S240505av: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S240505av: Identification of a GW compact binary merger candidate
- GRB 240502C: Zeiss-1000 at Koshka observatory observations of GOTO optical counterpart candidates
- GW170817: VLA observations at ~5.5 yrs since merger
- GRB 240502C: GOTO possible optical counterpart candidates
- LIGO/Virgo/KAGRA S240501an: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S240501an: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S240430ca: Identification of a GW compact binary merger candidate
- Additional DECam GW-MMADS Candidates from three nights of observations
- LIGO/Virgo/KAGRA S240426s: Updated Sky localization
- LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limit for EP240426a
- LIGO/Virgo/KAGRA S240426dl: Updated Sky localization
- LIGO/Virgo/KAGRA S240428dr: Updated Sky localization
- LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet ToO observations
- LIGO/Virgo/KAGRA S240429an: Retraction of GW compact binary merger candidate
- LIGO/Virgo/KAGRA S240428dr: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S240422ed: J-band non-detection of J-GEM24a
- LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
- LIGO/Virgo/KAGRA S240422ed: Observations with 1.6m Mephisto
- LIGO/Virgo/KAGRA S240422ed: A transient discovered from Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
- LIGO/Virgo S240422ed: Swift XRT observation of EP240426a
- LIGO/Virgo/KAGRA S240422ed: NOT optical observations of EP240426a
- LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfq, AT2024hfr, AT2024hfs, and AT2024hfx
- LIGO/Virgo/KAGRA S240422ed: GRANDMA Optical Upper Limits for EP240426a
- LIGO/Virgo/KAGRA S240426dl: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S240422ed: BOOTES-4/MET Optical Upper Limits for EP240426a
- LIGO/Virgo/KAGRA S240422ed: Continued Magellan Observations
- EP240426a: GMG optical upper limit
- LIGO/Virgo/KAGRA S240422ed: EP-FXT detection of a candidate counterpart EP240426a
- LIGO/Virgo/KAGRA S240426s: Identification of a GW compact binary merger candidate
- 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
- S240422ed: BlackGEM/MeerLICHT transient detection AT2024hgl/MLTJ080628.10-250116.4
- LIGO/Virgo/KAGRA S240422ed: PRIME near-infrared observations
- S240422ed: MeerLICHT/BlackGEM photometry on AT2024hfx and archival ZTF detection
- LIGO/Virgo/KAGRA S240422ed: Second night Pan-STARRS observations of the skymap
- LIGO/Virgo/KAGRA S240422ed: Additional DECam GW-MMADS Candidates from the first two nights of 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 S240422ed: SRG/eROSITA archival upper limits for Swift/XRT candidates
- LIGO/Virgo/KAGRA S240422ed: Archival BlackGEM/MeerLICHT detections of AT 2024hdr & AT 2024hdq
- LIGO/Virgo/KAGRA S240413p: DESGW DECam Follow-Up
- LIGO/Virgo/KAGRA S240422ed: No significant counterpart candidates in HAWC observations
- LIGO/Virgo/KAGRA S240422ed: Vetting of DECam Candidates Using Real-Time Resources and SAGUARO Infrastructure
- LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA/FRAM Observations
- IceCube-240424A - IceCube observation of a high-energy neutrino candidate track-like event
- 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: Early X-ray Upper Limits from EP-WXT for the LVK Sky Localization Region
- 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: SAGUARO upper limits from CSS
- LIGO/Virgo/KAGRA S240422ed: LAST optical observations
- LIGO/Virgo/KAGRA S240421ar: Updated Sky localization
- LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from Pan-STARRS observations of the skymap
- LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search
- LIGO/Virgo/KAGRA S240423br: Retraction of GW compact binary merger candidate
- LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS 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: Updated NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S240422ed: AstroSat CZTI non-detection and upper limits
- LIGO/Virgo/KAGRA S240422ed: Upper limits from Fermi-GBM Observations
- LIGO/Virgo/KAGRA S240422ed: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S240421ar: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S240422ed: Coverage and upper limits from MAXI/GSC observations
- LIGO/Virgo/KAGRA S240422ed: Identification of a GW compact binary merger candidate
- LIGO/Virgo/Kagra S240422ed: NED Galaxies in the Localization Volume
- GRB 240414A: AMI-LA radio observations
- 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: NOT optical counterpart candidate and potential host
- GRB240418A - Candidate afterglow from NIRES