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"- INTEGRAL Alert n.6678: NOT A GRB
- GRB 121011A: optical observations
- GRB 121011A: Swift/UVOT Detection
- IPN Triangulation of short hard GRB 121011B
- GRB 121011A: NOT redshift retraction
- GRB 121011A: misprint in GCNC 13854
- GRB 121011A: Fermi GBM observation
- GRB 121011A: Fermi-LAT detection of a burst
- Swift-BAT trigger 535733 is not astrophysical
- GRB 121011A: Swift-XRT refined Analysis
- GRB 121011A: NOT optical observations
- GRB 121011A: optical observations
- GRB 121011A: MASTER-Net bell light curve
- GRB 121011A: TNG optical observations
- GRB 121011A, Swift-BAT refined analysis
- Swift-BAT refined analysis of the SGR 1806-20 outburst (trigger 535747)
- GRB 121011A: Enhanced Swift-XRT position
- Planned XMM-Newton and IRAM observation of GRB 121011A
- GRB 121011A: MASTER-Net early OT light curve
- GRB121011A : Xinglong TNT optical observation
- GRB 121011A: MITSuME Okayama Optical Observation
- GRB 121011A: Swift detection of a burst with optical afterglow
- Trigger 535747: Swift detection of an outburst from SGR1806-20
- Trigger 535733: Swift possible detection of SAX J1828.5-1037
- GRB 120927A: optical upper limit
- GRB 120804A: Late-time Chandra observation
- GRB 121001A: GROND Afterglow Confirmation
- GRB 121001A: Swift/UVOT Upper Limits
- GRB 121001A: Swift-XRT refined Analysis
- GRB 121001A: Enhanced Swift-XRT Position
- Swift Trigger 535026 is GRB 121001A: Swift-BAT refined analysis
- Swift Trigger 535026: Optical decay confirmation with IAC80 and BOOTES-2/TELMA.
- GRB 121001A: MASTER optical observations
- GRB 121001A: possible optical counterpart
- Swift Trigger 535026: ROTSE-III Optical Limits
- Swift Trigger 535026: Galactic Transient or possible GRB
- GRB 120927A: Swift/UVOT Upper Limits
- GRB 120927A, Swift-BAT refined analysis
- GRB 120927A: GROND upper limits
- GRB 120927A: Swift-XRT refined Analysis
- GRB 120923A: Correction to GCN 13823
- GRB 120927A: Enhanced Swift-XRT position
- GRB 120923A: JHK Observation
- GRB 120927A: Swift detection of a burst
- Further Swift-XRT observations of the GRB 120919A field.
- GRB 120923A: optical upper limit
- GRB 120921A: Fermi GBM detection of its 1000th GRB
- GRB 120923A: RAPTOR Early Afterglow Limits
- GRB 120923A: MITSuME Okayama Optical upper limits
- GRB 120916A Suzaku WAM observation of the prompt emission
- GRB 120923A: RAPTOR Limits During Gamma-Ray Emitting Interval
- GRB 120923A: CARMA Observations
- GRB 120923A: EVLA Observations
- GRB 120923A: Swift-XRT refined Analysis
- GRB 120923A: GROND Upper limits
- GRB 120922A: GROND photometric redshift
- GRB 120922A: Fermi GBM detection
- GRB 120922A: Swift/UVOT Detection
- GRB 120923A: Swift-BAT refined analysis
- GRB 120922A: Swift-BAT refined analysis
- GRB 120923A: Swift/UVOT Upper Limit
- GRB 120922A: Swift-XRT refined Analysis
- GRB 120922A: Swift/UVOT Observations
- GRB 120923A: Gemini afterglow detection, high-z candidate
- GRB 120923A: Enhanced Swift-XRT position
- GRB 120922A: Enhanced Swift-XRT position
- GRB 120922A: TAROT La Silla observatory optical observations
- GRB 120923A: TAROT La Silla observatory optical observations
- GRB 120923A: ROTSE-III Optical Limits
- GRB 120923A: Swift detection of a burst
- GRB 120922A: GROND afterglow candidate
- GRB 120922A: Prompt enhanced Swift-XRT position
- GRB 120922A: Swift detection of a burst
- GRB 120919B: MASTER prompt optical observations
- GRB 120919A: Swift/UVOT Upper Limits
- GRB 120919A: Swift-XRT observations
- Konus-Wind observation of GRB 120919B
- IPN Triangulation of long GRB 120919B
- Konus-Wind observation of GRB 120919A
- IPN Triangulation of long GRB 120919A
- GRB 120919A: Fermi GBM detection
- GRB 120918A: Swift-BAT refined analysis
- Swift trigger 534017 was not an astrophysical event
- GRB 120916A: Fermi GBM Observation
- Konus-Wind observation of GRB 120916A
- Swift Trigger 534017 is probably not real.
- GRB 120918A: Swift detection of a burst
- IPN Triangulation of long GRB 120916A
- GRB 120916A: Fermi-LAT detection of a burst
- Corrections to the Fermi-LAT upper limits for GRB 120807A, 120908A, 120909A, and 120911A
- Swift Transient Swift J174510.8-262411: Swift-BAT refined analysis
- Swift Trigger 533836 is a new Galactic transient
- GRB 120913B: Fermi GBM observation
- GRB 120913B: Swift-BAT refined analysis
- GRB 120913A: Fermi GBM observation
- GRB 120913B: FRAM early follow up and detection
- GRB 120913A: Swift-BAT refined analysis
- GRB 120913B: REM NIR early time detection
- Continued Skynet/PROMPT observations of GRB120913B
- GRB 120913B: TAROT La Silla observatory optical photometry