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 090429D: Fermi GBM detection
- GRB 090429C: Fermi GBM detection
- GRB 090429B: Swift/UVOT Upper Limits
- GRB 090429A: Swift/UVOT Upper Limits
- GRB 090427: pseudo-z= 1.48 from prompt emission spectrum
- GRB 090429B: Gemini-N further nIR observations
- GRB 090424: YNAO-GMG observations
- GRB 090429A: Swift-XRT refined analysis
- GRB 090429A: GROND upper limits
- GRB 090427C: Fermi GBM detection
- GRB 090427B: Fermi GBM detection
- GRB 090426C: Fermi GBM detection
- GRB 090426B: Fermi GBM detection/observation
- GRB 090429B: Swift XRT refined analysis
- GRB 090429A: Enhanced Swift-XRT position
- Konus-Wind observation of very bright GRB 090427
- GRB 090428B: Fermi GBM detection
- GRB 090428: Fermi GBM detection
- GRB 090418A BVRcIc field calibration
- GRB 090426: GAO 150cm telescope Optical Observation
- GRB 090429B: RIMOTS optical upper limits
- GRB 090429B: Swift-BAT refined analysis
- GRB 090429A: Swift-BAT refined analysis
- GRB 090429B: Enhanced Swift-XRT position
- GRB 090429A - Correction to XRT position
- GRB090429B: Gemini-N infrared IR candidate
- GRB 090426: YNAO-GMG observations
- GRB 090429B: VLT upper limits
- GRB 090429B: GROND Observations
- GRB 090429B: Super-LOTIS early observations
- GRB 090429B: Swift detection of a burst
- GRB 090429: Swift detection of a burst
- GRB 090423: pseudo burst at z=1 and its relation to GRB 080913
- GRB 090424 : Multiband Optical observation from Nainital
- IPN triangulation of very bright GRB 090427
- GRB 090426: R-band limit
- GRB 090424: Continued R-band monitoring
- GRB 090423: CARMA mm observations
- GRB 090423: millimeter detection
- GRB 090426: Swift/BAT spectral lag results
- GRB 090425: Fermi GBM detection
- GRB 090424: Suzaku WAM observation of the prompt emission
- GRB 090426: VLT spectroscopy
- GRB 090426: GROND Observations of the Optical/NIR Afterglow
- GRB 090426: Near infrared observation with ISLE at OAO
- GRB 090426: Okayama MITSuME optical observation
- GRB090426 Swift/UVOT observations
- GRB 090426 Keck LRIS redshift
- GRB 090426: Swift-BAT refined analysis
- GRB 090426: Swift-XRT refined analysis
- GRB 090423: GROND second epoch imaging and refined SED
- Detection of bright radio afterglow of GRB 090424 with the VLA
- GRB 090426: Enhanced Swift-XRT position
- GRB090426: Observation for Optical counterpart from MIRO
- GRB 090426, RIMOTS optical upper limits
- GRB 090426: inspection of SDSS images
- GRB 090426: TNT confimation of optical counterpart
- GRB 090426: Swift detection of a burst with an optical counterpart
- GRB090424: R-band detection (37.5 hrs post-burst), jet break?
- GRB 090424: MASTER-Net prompt optical limit
- GRB 090423: Fermi GBM observation (correction of isotropic equivalent energy)
- GRB 090424: WHT ISIS spectroscopy
- VLA radio observation of high-z GRB 090423
- GRB090424: BVRI/R-band detection after 15 hrs burst
- GRB 090424 : Lulin 1m telescope optical observations
- GRB 090424: THO optical observations
- GRB 090424: GROND Observations of the Optical/NIR Afterglow
- GRB090423: Y-band limit
- GRB 090424 Gemini-South Redshift
- GRB 090423: Y-band field calibration update/correction
- GRB 090423: Swift/BAT spectral lag results
- GRB 090424 : TAOS optical detection
- GRB 090424 optical observations
- GRB 090424: Liverpool Telescope observations
- GRB 090424: Swift-XRT refined analysis
- GRB 090424: Optical observations from 1.23m CAHA
- GRB 090423: energetic, luminosity and jet break
- Swift/UVOT observations of GRB 090424
- GRB 090424: MASTER-Net prompt optical observations
- GRB 090424: Enhanced Swift-XRT position
- GRB 090424: Swift-BAT refined analysis
- GRB 090424: Fermi GBM Observation
- GRB 090423: Fermi GBM observation
- GRB 090422: Fermi GBM observation
- GRB 090423: Ep,i - Eiso correlation
- GRB 090424: SDSS Galaxy at the Swift position
- GRB 090424: TNT optical observations
- GRB 090424: ROTSE-III Confimation of Optical Counterpart
- GRB 090424: Swift detection of a burst with an optical counterpart
- GRB 090423: Refined TNG analysis
- GRB090423: Y-band field calibration
- GRB 090423 limiting magnitudes
- GRB 090423: VLT/ISAAC spectroscopy
- GRB 090423: Near infrared observation at Okayama Observatory
- GRB 090423: Deep z-band upper limit and confirmation of photo-z
- GRB 090423: TNG Amici spectrum
- GRB 090423: GROND detection and preliminary photo-z
- GRB 090423: NOT z-band limit
- GRB 090423: Correction to NIR photometry
- GRB 090423: Swift-XRT refined analysis