GCN Circulars
GCN Circulars are rapid bulletins submitted by and distributed to the community. 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').
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"- GRB 250911A: GECAM-B detection
- GRB 250911A: Swift-BAT refined analysis
- 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
- GRB 250911A: MASTER optical counterpart observations
- EP250911a: SAO RAS optical observations
- GRB 250911A: Swift-XRT refined Analysis
- GRB 250910C: Fermi GBM Final Localization Correction
- EP250911a: Swift-XRT 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
- GRB 250909B: Insight-HXMT detection
- GRB 250909B: SVOM/GRM observation
- LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
- GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
- EP250911a: COLIBRÍ optical observations
- 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
- EP250911a: Einstein Probe detection of an X-ray transient
- 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: Enhanced Swift-XRT position
- GRB 250911A: Swift-XRT observations
- GRB 250911A: COLIBRÍ optical counterpart candidate
- GRB 250911A: Swift detection of a burst
- LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
- GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
- GRB 250910B: Fermi GBM Final Real-time Localization
- 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
- 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 250910A: SVOM detection of a faint burst
- LIGO/Virgo/KAGRA S250910b: Retraction of GW compact binary merger candidate
- GRB 250702B: Late time Chandra observations
- EP250908b/EP#01709240653: Swift/UVOT Detection
- EP#01709240653: Swift-XRT observations
- The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
- 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
- The EP-WXT trigger EP250908a/01709240652 is not a real source
- EP250908c: Global MASTER-Net observations report
- Fermi GRB 250909A: Global MASTER-Net observations report
- EP250908c: Einstein Probe detection of an X-ray transient
- GRB 250909A: Fermi GBM Final Real-time Localization
- EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
- EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
- LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
- GRB 250907A: GECAM-B detection
- 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
- 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
- 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
- EP250905b: EP-WXT detection of a fast X-ray transient
- EP250905a: FTW one optical and multiple NIR counterpart candidates
- GRB 250905A: Swift-XRT refined Analysis
- EP250905a: JinShan likely optical counterpart detection
- IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 250904A: Swift-BAT refined analysis
- IceCube Alert 250905.84: Global MASTER-Net observations report
- GRB 250905A: Swift/UVOT Upper Limits
- EP250905a: Global MASTER-Net observations report
- GRB 250901A - SVOM/ECLAIRs refined analysis
- EP250905a: Einstein Probe detection of an X-ray transient
- GRB 250905B: Fermi GBM Final Localization
- GRB250904A: Liverpool Telescope upper limits
- GRB 250905A: Enhanced Swift-XRT position
- GRB 250904A: Swift/UVOT Detection
- GRB 250903A: Swift/UVOT detection
- GRB 250904A: Swift-XRT refined Analysis
- LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
- LIGO/Virgo/KAGRA S250904br: Updated Sky localization
- EP detected a brightening of LMXB 1ES 1735-26.9
- GRB 250905A: KAIT optical upper limit
- GRB 250905A: Swift detection of a burst