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"20364 results found.
- GRB 250916A: OSIRIS+/GTC redshift z = 2.015
- GRB 250916A: MAO/AZT-22 optical observations
- GRB 250916A: SAO RAS optical observations
- GRB 250916A : GIT optical observations
- LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
- GRB250917B: WFST optical observations
- GRB 250917B: Swift-XRT observations
- GRB 250917B: Swift detection of a short burst
- GRB 250916A: GOTO optical counterpart candidate
- GRB 250916A: AstroSat CZTI detection of a bright long burst
- GRB 250910A: SVOM/ECLAIRs refined analysis
- EP250916a: Einstein Probe detection of an X-ray transient
- EP250827b: VLA Observations
- SVOM/sb25091517: SVOM detection of an X-ray transient
- GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
- GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
- GRB250912A: VLT/HAWK-I follow-up observations
- GRB 250912A: Fermi GBM Observation
- GRB 250912A:SVOM/VT optical upper limit
- GRB 250912A: LCO optical upper limit
- GRB 250912A: SVOM detection of a burst
- IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
- EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
- LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
- EP250911a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250910B: SVOM/GRM observation
- EP250911a: SVOM/VT optical observation
- EP250911a: SAO RAS optical observations
- EP250911a: Optical detection with Kinder observations
- GRB 250911A: Swift/UVOT Detection
- GRB 250910A / EP250910a: Swift-XRT afterglow detection
- GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
- LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
- GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
- EP250911a: COLIBRÍ optical observations
- EP250911a: Einstein Probe detection of an X-ray transient
- LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
- GRB 250903A: SVOM/ECLAIRs refined analysis
- GRB 250911A: Enhanced Swift-XRT position
- GRB 250911A: Swift-XRT observations
- GRB 250911A: COLIBRÍ optical counterpart candidate
- GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
- EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
- GRB 250909B: AstroSat CZTI detection of a long burst
- GRB 250910A: SVOM/VT optical upper limit
- GRB 250910A: LCO optical upper limit
- GRB 250702B: Late time Chandra observations
- EP250908b/EP#01709240653: Swift/UVOT Detection
- EP250908c: refined analysis of the EP-WXT and EP-FXT observations
- EP250908c: SVOM/VT optical observation
- EP250908c: VLT/FORS2 optical counterpart identification
- EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
- EP250908b: SVOM/VT optical candidate
- EP250908c: Einstein Probe detection of an X-ray transient
- EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
- Fermi-LAT Gamma-ray Observations of IceCube-250905A
- GRB 250903A: Swift-XRT afterglow detection
- LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
- IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
- SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
- EP250905a: Liverpool Telescope i-band upper limits
- LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
- EP250905a: Liverpool Telescope observations
- EP250905a: refined analysis of the EP-WXT and EP-FXT observations
- EP250905b: EP-WXT detection of a fast X-ray transient
- EP250905a: JinShan likely optical counterpart detection
- GRB 250905A: Swift/UVOT Upper Limits
- GRB 250901A - SVOM/ECLAIRs refined analysis
- EP250905a: Einstein Probe detection of an X-ray transient
- GRB250904A: Liverpool Telescope upper limits
- GRB 250905A: Enhanced Swift-XRT position
- GRB 250904A: Swift/UVOT Detection
- GRB 250903A: Swift/UVOT detection
- EP detected a brightening of LMXB 1ES 1735-26.9
- GRB 250905A: KAIT optical upper limit
- GRB 250905A: Swift detection of a burst
- GRB 250904A: Enhanced Swift-XRT position
- IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250904A: TRT optical counterpart detection
- GRB 250904A: Swift detection of a burst
- LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
- EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
- EP-WXT trigger 01709201209: Liverpool Telescope upper limits
- EP250903a: refined analysis of the EP-WXT and EP-FXT observations
- LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
- GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
- LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
- GRB 250903A: LCO optical observation
- GRB 250903A: LCO optical afterglow detection
- GRB 250903A: SVOM/VT optical confirmation with VHF data
- EP250901a: Mondy, Assy and SAO RAS optical limits
- GRB 250903A: TRT optical counterpart detection
- GRB 250903A: SVOM detection of a burst
- EP250903a: TRT optical observations
- EP250903a: Einstein Probe detection of an X-ray transient
- EP 250827B: Detection of supernova counterpart by LCO.
- EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
- GRB 250902B: SVOM/GRM observation
- EP250827b: SVOM/VT observation of AT 2025wkm
- LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data