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"32490 results found.
- LIGO/Virgo/KAGRA S250908y: Updated Sky localization
- Fermi GRB 250910B: Global MASTER-Net observations report
- EP250911a: LCO optical counterpart discovery
- EP250910a: Global MASTER-Net observations report
- GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
- LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
- GRB 250903A: SVOM/ECLAIRs refined analysis
- GRB 250911A: COLIBRÍ optical counterpart candidate
- LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
- GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
- EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
- GRB 250910A: SVOM/VT optical upper limit
- EP250908C: GROND observation of the fading optical counterpart
- GRB 250910A: LCO optical upper limit
- GRB 250909A: AstroSat CZTI detection
- GRB 250910A: SVOM/MXT possible afterglow detection
- GRB 250702B: Late time Chandra observations
- EP250908b/EP#01709240653: Swift/UVOT Detection
- EP250908c: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250907A: CALET Gamma-Ray Burst Monitor detection
- 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: Global MASTER-Net observations report
- Fermi GRB 250909A: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
- GRB 250905A: Swift-BAT refined analysis
- 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
- EP250905a: Liverpool Telescope i-band upper limits
- LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
- EP250905b: EP-FXT follow-up observation
- LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
- EP250905a: Liverpool Telescope observations
- EP250905a: refined analysis of the EP-WXT and EP-FXT observations
- EP250905b: Global MASTER-Net observations report
- EP250905a: FTW one optical and multiple NIR counterpart candidates
- EP250905a: JinShan likely optical counterpart detection
- GRB 250904A: Swift-BAT refined analysis
- GRB 250905A: Swift/UVOT Upper Limits
- EP250905a: Global MASTER-Net observations report
- GRB 250901A - SVOM/ECLAIRs refined analysis
- GRB250904A: Liverpool Telescope upper limits
- GRB 250904A: Swift/UVOT Detection
- GRB 250903A: Swift/UVOT detection
- LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
- LIGO/Virgo/KAGRA S250904br: Updated Sky localization
- GRB 250905A: KAIT optical upper limit
- Swift GRB 250904A: Global MASTER-Net observations report
- GRB 250904A: TRT optical counterpart detection
- EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
- GRB 250902B: CALET Gamma-Ray Burst Monitor detection
- EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
- GRB 250902A: CALET Gamma-Ray Burst Monitor detection
- LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
- GRB 250902A: VZLUSAT-2 detection
- LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
- GRB 250903A: Swift-XRT observations
- EP250903a: Swift-XRT observations
- EP#01709201209: Swift-XRT observations
- EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
- EP-WXT trigger 01709201209: Liverpool Telescope upper limits
- GRB 250830C: VZLUSAT-2 detection
- 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: EP-FXT counterpart detection
- GRB 250902A: GECAM-B detection
- GRB 250903A: LCO optical observation
- GRB 250903A: LCO optical afterglow detection
- GRB 250903A: SVOM/VT optical confirmation with VHF data
- EP250903a: SVOM/VT optical confirmation
- EP250901a: Mondy, Assy and SAO RAS optical limits
- Subject GRB 250903A: SVOM/MXT afterglow detection
- EP250903a: LCO candidate counterpart discovery
- GRB 250903A: TRT optical counterpart detection
- GRB 250902B: AstroSat CZTI detection
- EP250903a: Global MASTER-Net observations report
- EP250903a: TRT optical observations
- EP250903a: Einstein Probe detection of an X-ray transient
- EP 250827B: Detection of supernova counterpart by LCO.
- EP250827b / AT 2025wkm: TRT optical observations
- EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
- EP250827b: continued Liverpool Telescope observations
- 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
- GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
- Fermi GRB 250902B: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-250831A
- GRB 250902A: Fermi GBM Detection
- GRB 250901A: Swift/UVOT Upper Limit
- IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
- EP250827b: Liverpool Telescope observations
- GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT