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.
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 191009A: Insight-HXMT/HE detection
- GRB 191011A: MASTER OT retraction.
- GRB 191011A: Enhanced Swift-XRT position
- GRB 191011A: correction of reported magnitudes
- GRB 191011A: BALROG localization (Fermi Trigger 592461363 / GRB 191011192)
- GRB 191011A: GROND Detection of the Optical/NIR afterglow
- GRB 191011A: VLT X-shooter redshift from RRM Observations
- Swift GRB191011.19: Global MASTER-Net observations report
- Swift GRB191011.19: Global MASTER-Net OT detection
- GRB 191011A: Swift detection of a burst with an optical counterpart
- GRB 191011A: Fermi GBM Final Real-time Localization
- GRB 191009A: BALROG localization (Fermi Trigger 592297741 / GRB 191009298)
- GRB 191009A: Fermi GBM Final Real-time Localization
- LIGO/Virgo S190930t: Continued Swift observations of AT2019sbk
- Fermi trigger No 592211224: Global MASTER-Net observations report
- TESS Detection of the Optical Emission from the Possible Untriggered GRB Associated with ZTF19abvizsw
- GRB 191004A: CALET Gamma-Ray Burst Monitor detection
- Fermi trigger No 592211224: Global MASTER-Net observations report
- GRB 191008A: Fermi GBM Final Real-time Localization
- GRB 191004B: Swift/UVOT Detection
- GRB 191004B: Continued Optical Afterglow Monitoring with LCO
- GRB 191004B: Correction to Konus-Wind GCN 25974
- Fermi/GBM observation of a bright burst from magnetar SGR 1935+2154
- Konus-Wind observation of GRB 191004B
- Konus-Wind observation of GRB 191004A
- GRB 191004A: Swift/UVOT Detection
- GRB 191004A: Optical Detection with LCO
- LIGO/Virgo S190930s: no counterpart candidate in the SVOM/GWAC observations
- LIGO/Virgo S190930s: Updated Sky Localization
- LIGO/Virgo S190930t: Magellan/IMACS imaging of Swift J224718-581442 (AT2019sbk)
- LIGO/Virgo S190930t: Swift XRT observations, no secure afterglow found
- GRB 190928A: AstroSat CZTI detection
- LIGO/Virgo S190930t: Swift discovery of Swift J224718-581442 (AT2019sbk): a fading UV transient with an X-ray counterpart
- LIGO/Virgo S190930t: Swift J221951-484240 optical photometry of Chilescope observatory
- LIGO/Virgo S190930t: SALT optical spectroscopy of Swift J221951-484240
- GRB 191004B: Swift-XRT refined Analysis
- GRB 191004B: GROND Detection of the Optical/NIR Afterglow
- GRB 191004A: GROND Upper limits
- GRB 191004B: COATLI Optical Observations
- GRB 191004A: Swift-XRT refined Analysis
- GRB 191004B: VLT/X-shooter redshift
- GRB 191004B: Swift-BAT refined analysis
- GRB 191004B: NOT optical photometry
- GRB 191004A: Swift-BAT refined analysis
- GRB 191004A: NOT optical upper limits
- GRB 191004B: Enhanced Swift-XRT position
- GRB 191004A: Enhanced Swift-XRT position
- GRB 191004B: Optical Afterglow Detection with LCO
- Swift GRB191004.9: Global MASTER-Net OT detection
- GRB 191004B: Swift detection of a burst with an optical counterpart
- FACT follow-up of IceCube-191001A
- GRB 191004A: Swift detection of a burst with an optical detection
- Swift GRB191004.75: Global MASTER-Net OT detection
- LIGO/Virgo S190930t: AT2019rpn, AT2019rpj CrAO continued optical photometry
- GRB 191001A: Swift-XRT observations
- LIGO/Virgo S190930t: J-GEM follow-up observation for Swift J221951-484240
- GRB 191001B: Optical Upper Limits with LCO
- LIGO/Virgo S190930t: Continued Swift/UVOT observations of Swift J221951-484240
- GRB 191001A: Fermi GBM observation
- GRB 190926A: Upper limit from CAHA 2.2m observation
- IceCube-191001A: HAWC follow-up
- GRB 190919A: AstroSat CZTI detection
- LIGO/Virgo S190930t: Upper limits from Insight-HXMT/HE observations
- LIGO/Virgo S190930s: Upper limits from Insight-HXMT/HE observations
- Fermi-LAT Gamma-ray Observations of IceCube-191001A
- LIGO/Virgo S190930t: Palomar 200-in DBSP spectroscopy of ZTF19acbwaah
- GRB 191001B: Swift-BAT refined analysis
- IceCube-191001A: Candidate Counterparts with the Zwicky Transient Facility
- LIGO/Virgo S190930t: AT2019rpn, AT2019rpj CrAO optical photometry
- IceCube-191001A: Not observable by Fermi-GBM
- IPN triangulation of GRB 191001A
- LIGO/Virgo S190930t: No neutrino candidates at Pierre Auger Observatory
- GRB 191001A: Swift ToO observations
- LIGO/Virgo S190930t: ATLAS Forced photometry of ZTF19acbpqlh (AT2019rpn)
- LIGO/Virgo S190930t: Candidates from ATLAS observations and constraints on AT2019rpr and AT2019rpn
- LIGO/Virgo S190930t: Palomar 200-in DBSP follow-up of ZTF19acbpqlh and ATLAS19wyn
- LIGO/Virgo S190930t: J-GEM follow-up observations for AT2019rpj
- GRB 191001A: KAIT Optical Upper Limit
- GRB 191001A: RATIR Optical and NIR Observations
- LIGO/Virgo S190930t: HCT observations of ZTF19acbpsuf
- LIGO/Virgo S190930t: Lulin Follow-up Observations of AT2019rpn and AT2019rpj
- LIGO/Virgo S190930s: no counterpart candidates in SAGUARO/CSS observations
- IceCube-191001A: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
- IceCube-191001A - IceCube observation of a high-energy neutrino candidate event
- LIGO/Virgo S190930s: No counterpart candidates in KAIT observations
- GRB 191001A: DDOTI Optical Counterpart Candidate
- IceCube Alert 191001.84: Global MASTER-Net observations report
- LIGO/Virgo S190924h: Correction to GCN 25905, updated sky localization for S190924h
- LIGO/Virgo S190930t and S190930s: MASTER OT J205529.78+220725.5/AT2019rpr further analysis
- LIGO/Virgo S190930t: Upper limits on the two of the ZTF/GROWTH candidates
- GRB 191001B: MITSuME Akeno optical upper limits
- LIGO/Virgo S190828h: Updated Sky Localization
- LIGO/Virgo S190814bv: VLA 6 GHz observations of 75 galaxies in the 90% localization region
- LIGO/Virgo S190923y: optical spectrum of MASTER detected transient
- GRB 191001B: Swift detection of a burst
- LIGO/Virgo S190930t: Transient found in Swift/UVOT counterpart search
- LIGO/Virgo S190930t and S190930s: MASTER PSN in unknown disk galaxy
- LIGO/Virgo S190930t: Candidates from the Zwicky Transient Facility
- LIGO/Virgo S190930t: No counterpart candidates in Fermi-LAT observations
- LIGO/Virgo S190930t and S190930s: MASTER optical observation and optical transient