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.
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"- GW170817/GRB170817A: LBT optical detection
- GRB 180603A: AstroSat CZTI detection
- Fermi GBM trigger 180604900/549840956 likely not a GRB
- GRB 180602A: MITSuME Ishigakijima optical upper limits
- GRB 180602B: Fermi GBM detection
- GRB 180602A: Swift/UVOT Upper Limits
- GRB 180602A: MITSuME Akeno optical upper limits
- GRB 180602A: Swift-XRT refined Analysis
- GRB 180602A: Swift-BAT refined analysis
- GRB 180602A: MITSuME Okayama optical upper limits
- GRB 180602A: Enhanced Swift-XRT position
- GRB 180602A: Swift detection of a burst
- Fermi GBM trigger 549533811/180601345 is not a GRB
- Konus-Wind observation of GRB 180529A
- GRB 180529A: CALET Gamma-Ray Burst Monitor detection
- IPN Triangulation of GRB 180529A (short/hard)
- Swift Trigger 834937 is not a GRB
- Konus-Wind observation of GRB 180526A
- IPN Triangulation of GRB 180526A (long)
- GRB 180526A: CALET Gamma-Ray Burst Monitor detection
- Konus-Wind observation of GRB 180523A
- GRB 180526A: AstroSat CZTI detection
- AGILE/MCAL detection of GRB 180529 and a possible precursor
- IPN Triangulation of GRB 180523A
- GRB180523B: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 548793993)
- GRB 180523A: CALET Gamma-Ray Burst Monitor detection
- Fermi GBM trigger 548829437/180524192 is not a GRB
- GRB 180514A: MITSuME Ishigakijima optical upper limits
- GRB 180514A: CrAO/ZTSH optical observations and afterglow candidate
- GRB 180505A: AstroSat CZTI detection
- GRB 180514A: Swift/UVOT Upper Limits
- GRB 180514A: MITSuME Akeno optical upper limits
- GRB 180514A: Detection limits from 2.5m NOT
- GRB 180510A: MITSuME Ishigakijima optical upper limits
- GRB 180514A: 1.5m OSN optical observations
- GRB 180514A: GOTO Optical Observations
- GRB 180514A: Swift-BAT refined analysis
- GRB 180514A: Swift-XRT refined Analysis
- GRB 180514A: Enhanced Swift-XRT position
- GRB 180512A: VLT/HAWK-I NIR Observations
- GRB 180514A: Swift detection of a burst
- Konus-Wind observation of GRB 180510A
- GRB 180512A: Swift-XRT refined Analysis
- GRB 180512A: Swift-BAT refined analysis
- GRB 180512A: RATIR Optical Observations
- GRB 180512A: LBT optical detection
- GRB 180512A: Swift/UVOT Upper Limits
- GRB 180512A: LT prompt observations
- GRB 180512A: Enhanced Swift-XRT position
- GRB 180512A: GROND upper limits
- GRB 180512A: NOT upper limits
- GRB 180512A: OASDG optical observations
- GRB 180512A: Upper limits from OSN
- GRB 180512A: Swift detection of a burst
- GRB 180510A: Swift/UVOT followup observations
- GRB 180510B: Swift-XRT refined Analysis
- GRB 180510A: Swift-XRT refined Analysis
- Swift trigger 831888: misidentification of 4U 1416-62
- GRB 180510B: Swift-BAT refined analysis
- GRB 180510B: VLT/X-shooter observations
- GRB 180510B: GROND detection in all bands
- GRB 180510B: TAROT La Silla observatory optical observations
- Swift Trigger 831888: a possible GRB or Galactic transient
- GRB 180510B: Enhanced Swift-XRT position
- GRB 180418A: 15 GHz upper limits from AMI
- GRB 180510B: Swift detection of a burst with an optical counterpart
- GRB 180510A: Swift detection of a burst
- GRB 180427A: AstroSat CZTI detection
- Chandra observations of GW170817 reveal a fading afterglow
- Chandra observations of GW170817 260 days since merger: first statistically significant evidence for an X-ray decay
- GRB 180504A: Swift/UVOT Upper Limits
- GRB 180504A: Swift-BAT refined analysis
- GRB 180505A: Fermi GBM detection
- GRB 180416A: AstroSat CZTI detection
- GRB 180504A: ePESSTO NTT NIR observations
- Correction to Swift-XRT light curve fit for GRB 180504A in GCN 22685
- GRB 180504A: Swift-XRT refined Analysis
- GRB 180504A: NOT afterglow candidate
- GRB 180504A: Prompt enhanced Swift-XRT position
- GRB 180504A: Swift detection of a burst
- GRB 180416B: AstroSat CZTI detection
- Konus-Wind observation of GRB 180427A
- IPN Triangulation of GRB 180427A
- GRB 180427A: Fermi GBM detection
- Swift Trigger 829046 is probably noise
- GRB 180425A: Swift-XRT refined Analysis
- GRB 180425A: Swift-BAT refined analysis
- GRB 180425A: Swift/UVOT Upper Limits
- GRB 180425A: Enhanced Swift-XRT position
- GRB 180425A: Swift detection of a burst
- GRB 180418A: TAROT La Silla observatory early optical observations
- GRB 180418A: MITSuME Ishigakijima Optical Observation
- Retraction of IceCube GCN/AMON NOTICE 71165249_130949
- GRB 180418A : SQUEAN observations
- Fermi GBM trigger 545979055/180421202 is not a GRB
- GRB 180418A: Further GROND observations
- GRB 180418A: Swift/UVOT Detection
- GRB 180418A: Continued RATIR Optical Observations
- GRB 180418A: Imaging of the optical afterglow with the 1.3 m DFOT and 3.6 m DOT in ARIES, India
- GRB 180418A GROND observations