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"- GRB 090929: Enhanced Swift-XRT position
- GRB 090929B: Swift detection of a burst
- GRB 090929A: Fermi GBM detection
- GRB090926A: Swift-XRT refined analysis
- GRB 090927: Faulkes Telescope South Detection of the Optical Afterglow
- Konus-Wind and Konus-RF observations of GRB 090926A
- GRB 090927: VLT redshift
- GRB 090926B: Fermi GBM detection
- GRB 090927: Zadko Telescope observations
- GRB 090927, Swift-BAT refined analysis of the possibly short burst
- Swift/UVOT observations of GRB 090927
- GRB 090926A: Skynet/PROMPT Continued Observations
- GRB 090927: Swift XRT refined analysis
- GRB 090926A: Suzaku WAM observation of the prompt emission
- GRB 090927: Enhanced Swift-XRT position
- GRB090926B: Swift/UVOT Upper Limits
- GRB090926A: Swift/UVOT observations
- GRB 090926B: VLT spectroscopy
- GRB 090927: Swift/UVOT detection of an optical afterglow
- GRB 090927: Swift detection of a short burst
- GRB 090926B: optical object in error circle
- GRB 090926B: MAXI GSC detection
- GRB 090926A: VLT/X-shooter redshift
- GRB 090926B: NOT optical observation
- GRB 090926B: Swift XRT refined analysis
- GRB 090926B: Swift-BAT refined analysis
- GRB 090926A: Swift/UVOT detection of an optical afterglow
- GRB 090926A: Skynet/PROMPT Discovery of the Optical Afterglow
- GRB090926A: UVOT-enhanced XRT position
- GRB 090926B: Swift detection of a burst
- GRB 090926: Fermi LAT detection
- GRB 090926: Fermi GBM detection
- GRB 090925: Fermi GBM detection
- GRB090904B : IRSF NIR upper limit
- GRB090922A: correction to Fermi location
- GRB 090922A: Fermi GBM detection
- Swift returns to normal operations
- GRB 090715B: Skynet/PROMPT Detections
- GRB 090726: Skynet/GORT Observations
- GRB 090916: Swift-XRT upper limit
- GRB 090807: Skynet/DSO Observations
- GRB 090915: GROND upper limits
- Swift-BAT temporarily off-line for a few days
- Short-Duration GRB 090916: Skynet/PROMPT Observations
- GRB 090915: SARA detection of afterglow candidate
- GRB 090912: optical observation
- GRB 090915: Swift/UVOT detection of an optical afterglow candidate
- GRB 090702: Skynet/GORT Observations
- GRB 090902B: Skynet/PROMPT Observations
- GRB 090916, Swift-BAT refined analysis
- GRB 090915: Swift-XRT detection of a fading X-ray counterpart
- GRB 090916: Swift detection of a short burst
- GRB 090915 Swift-BAT detection of a burst in ground analysis
- GRB 090827: Confirmation of the X-ray afterglow
- GRB 090912: Swift-XRT refined analysis
- GRB 090912, Swift-BAT refined analysis
- GRB 090912: Swift/UVOT Upper Limits
- GRB 090912 optical upper limit
- GRB 090912: Enhanced Swift-XRT position
- GRB 090912: Swift detection of a burst
- GRB 090910: Fermi GBM detection
- GRB 090814A: Skynet/DSO & GORT Observations
- GRB 090823: Swift XRT confirmation of the X-ray afterglow
- GRB 090904B: GROND detection of the optical afterglow
- GRB 090831A: Suzaku WAM observation of the prompt emission
- GRB 090904A: Swift/UVOT Refined Analysis
- GRB 090904B: Swift/UVOT Refined Analysis
- GRB 090902B: Suzaku WAM observation of the prompt emission
- GRB 090829A: Suzaku WAM observation of the prompt emission
- GRB 090904B: Fermi GBM detection
- GRB 090904A: Swift-XRT refined analysis
- GRB 090904B: Swift XRT Refined Analysis
- GRB 090904B: MOA-II Optical observation
- GRB 090904A: Enhanced Swift XRT position
- GRB 090904B: Swift-BAT refined analysis
- GRB 090902B: VLA radio detection
- GRB 090904A: Swift-BAT refined analysis
- GRB 090904B: Enhanced Swift-XRT position
- GRB090904A: Correction to enhanced XRT position
- GRB 090904A: Enhanced Swift-XRT position
- GRB 090904A: NOT observations
- GRB 090902B: WSRT Radio Observation
- GRB090904B: REM observations
- GRB 090904B: Swift detection of a burst
- GRB 090904A: ROTSE-III Optical Limits
- GRB 090904: Swift detection of a burst
- GRB 090902B: ROTSE-III Detection of Optical Afterglow
- GRB 090902B: Swift/UVOT refined analysis
- GRB090902B: Swift XRT refined analysis
- GRB 090902B: Faulkes Telescope North observations
- GRB 090902B: GROND NIR Afterglow Observations
- GRB 090902B: Gemini-N absorption redshift
- GRB 090902B: Fermi LAT and GBM refined analysis.
- GRB 090902B: Enhanced Swift-XRT position
- GRB 090902B: Optical afterglow candidate
- GRB090902B: Swift/UVOT observations
- GRB 090902B: Swift/XRT Afterglow Candidate
- GRB 090902B: Fermi LAT detection
- GRB 090902B: Fermi GBM detection of a bright burst
- GRB 090902: Fermi GBM detection