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 210207B: LCO Optical Afterglow Detection
- GRB 210207B: KAIT Optical Observations
- GRB 210208A: A long GRB detected by INTEGRAL
- GRB 210207B: AGILE observations
- GRB 210207B: Swift-XRT refined Analysis
- Konus-Wind detection of GRB 210207B
- SGR 1935+2154: MAXI/GSC detection
- Konus-Wind detection of GRB 210204A (correction to GCN 29415)
- GRB 210207B: AbAO optical upper limit
- GRB 210207B: Enhanced Swift-XRT position
- GRB 210207B: optical detection with 3.6m Devasthal Optical Telescope
- GRB 210207B: Swift detection of a burst with a bright optical counterpart
- Fermi GRB 210207A: Global MASTER-Net observations report
- GRB 210207A: BALROG localization (Fermi Trigger / GRB 210207603)
- GRB 210204A (ZTF21aagwbjr/AT2021buv): Mondy and AbAO optical observations
- GRB 210207A: Fermi GBM Final Real-time Localization
- Konus-Wind detection of GRB 210204A / ZTF21aagwbjr
- GRB 210204A: Optical Observations from HCT
- GRB 210204A / ZTF21aagwbjr: Swift-XRT observations
- GRB 210204A: Swift ToO observations
- VLT/X-shooter redshift of 1.466 for ZTF21aagwbjr/AT2021buv, strengthening its association with GRB 210204A
- GRB 210204A: AstroSat CZTI Detection
- GRB 210205A: Swift-BAT refined analysis
- IPN triangulation of GRB 210204A
- GRB 210205A: Swift-XRT refined Analysis
- GRB 210205A: MITSuME Ishigaki optical observation
- ZTF21aagwbjr/AT2021buv: ZTF discovery of a fast optical transient likely associated with GRB 210104A
- GRB 210205B: AGILE/MCAL detection of a burst
- GRB 210205A: Swift/UVOT Upper Limits
- Swift GRB 210205A: Global MASTER-Net observations report
- GRB 210205A: Nanshan/NEXT optical upper limit
- GRB 210205A: BOOTES-4/MET optical upper limit
- GRB 210205A: Enhanced Swift-XRT position
- GRB 210205A： GWAC-F60A optical upper limit
- GRB 210205A: Swift detection of a burst
- Fermi GRB 210204B: Global MASTER-Net observations report
- Fermi GRB 210204A: Global MASTER-Net observations report
- GRB 210204B: Fermi GBM Final Real-time Localization
- GRB 210204: Fermi GBM observation
- GRB 210204A: GECAM detection
- GRB 210204A: BALROG localization (Fermi Trigger 634112970 / GRB 210204270)
- GRB 210204A: Fermi GBM Final Real-time Localization
- GRB 210202A: AGILE/MCAL detection
- Fermi GBM Observations of a bright burst from SGR J1935+2154
- GRB 210202A: Fermi GBM detection
- GRB 210202A: Fermi-LAT detection
- Fermi GRB 210202A: Global MASTER-Net observations report
- Fermi trigger No 633963272: Global MASTER-Net observations report
- Recent activity of SGR 1935+2154 as observed by CGBM
- GRB 210202A: BALROG localization (Fermi Trigger / GRB 210202841)
- INTEGRAL detection of a short burst from SGR 1935+2154
- GRB 210202A: Fermi GBM Final Real-time Localization
- GRB 210131A: GECAM detection
- Fermi trigger No 633879387: Global MASTER-Net observations report
- GECAM observations of SGR 1935+2154
- GRB 210129A: Insight-HXMT/HE detection
- Continued Chandra observations of GW170817 at ~3.3 years since merger
- Fermi GBM Observations of SGR J1935+2154
- Konus-Wind detection of two bright bursts from SGR 1935+2154
- GRB 140330A: Swift-XRT refined Analysis
- GRB 140320B: Swift-XRT refined Analysis
- GRB 140402A: Swift-XRT refined Analysis
- GRB 140104B: Swift-XRT refined Analysis
- GRB 210126A: AstroSat CZTI detection
- GRB 210124B: AstroSat CZTI detection
- GRB 210123A: AstroSat CZTI detection
- IPN triangulation of a bright burst from SGR 1935+2154
- ZTF21aaeyldq: Observations with the 3.6m DOT
- GECAM detection of a short burst probably from SGR 1935+2154
- GRB 210127A: Fermi GBM Final Real-time Localization
- GRB 210120A: Fermi GBM detection
- Fermi trigger No 633348010: Global MASTER-Net observations report
- HAWC Transient event on 2021/01/25
- Konus-Wind detection of GRB 210121A
- Konus-Wind detection of GRB 210124B
- GRB 210126A: GECAM detection
- IPN triangulation of GRB 210124B (short)
- GRB 210126A: BALROG localization (Fermi Trigger / GRB 210126417)
- GRB 210124B: Insight-HXMT/HE detection
- Fermi trigger No 633257525: Global MASTER-Net observations report
- GRB 210123A: Fermi GBM Final Localization
- GECAM detection of a burst possibly from the X-ray burster 4U 0614+09 or GRB 210124A
- GRB 210123A: Insight-HXMT/HE detection
- IPN triangulation of GRB 210121A
- GRB 210121A: GECAM detection
- GRB 210121A: Insight-HXMT/HE detection
- GRB 210120A : 1.3m DFOT optical observations
- ZTF21aaeyldq: GROND and CAHA jet break confirmation
- ZTF20aaeyldq: VLA radio detection
- GRB 210116A: AstroSat CZTI detection
- GRB 210120A(MASTER OT J105242.66+152355.0 / AT2021axc): Mondy optical observations
- GRB 210116: AstroSat LAXPC detection
- GRB 210120A: MASTER OT (possibly) discovery
- GECAM In-Flight Trigger of GRB 210120A
- GRB 210104A: 3.6m DOT optical upper limit
- Fermi GRB 210120A: Global MASTER-Net observations report
- GRB 210120A: BALROG localization (Fermi Trigger 632819449 / GRB 210120299)
- GRB 210120A: Fermi GBM Final Real-time Localization
- GRB 210112A: 3.6m DOT optical detection
- GRB 210119A (Swift J1851.2-6148): Swift-BAT refined analysis