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').
2808 results found.
- GRB 210706A: Swift-XRT afterglow detection
- GRB 210704A: Swift-XRT afterglow detection
- GRB 210702A: Swift-XRT refined Analysis
- GRB 210626A: Swift/XRT afterglow confirmation
- GRB 210626A: Swift-XRT afterglow detection
- GRB 210622A: Swift-XRT observations
- GRB 210618A: Swift-XRT afterglow detection
- GRB 210619B: Swift-XRT refined Analysis
- GRB 210618A: Swift-XRT observations
- Swift ToO Observations of HAWC transient J0020+3108
- GRB 210605B: Swift-XRT afterglow detection
- GRB 210610B: Swift-XRT refined Analysis
- GRB 210610A: Swift-XRT refined Analysis
- GRB 210606A: Swift-XRT afterglow detection
- GRB 210605B: Swift-XRT observations
- Initial results of a NICER X-ray monitoring of the magnetar, Swift J1555.2-5402
- Swift J1555.2-5402: Swift XRT refined analysis of the new SGR
- NICER discovery of 3.86 s pulsations from a new magnetar: SGR J1555.2-5402
- GRB 210527A: Swift-XRT refined Analysis
- GRB 210520A: Swift-XRT observations
- GRB210413B: further Swift-XRT observations
- GRB 210517A: Swift-XRT refined Analysis
- GRB 210514A: Swift/UVOT Upper Limits
- GRB 210515C: Swift-XRT refined Analysis
- GRB 210514A: Swift-XRT refined Analysis
- GRB 210514A: update on the BAT trigger time and burst duration
- GRB 210509A: Swift-XRT refined Analysis
- GRB 210506A: Swift-XRT observations
- GRB 210504A: Swift-XRT refined Analysis
- GRB 210413B: Swift/UVOT Observations
- GRB 210323B: Swift-XRT observations
- Swift Trigger 1045571 is not a GRB
- GRB 210421B: Swift-XRT observations
- GRB 210420B: Swift-XRT refined Analysis
- GRB 210421A: Swift-XRT refined Analysis
- GRB 210419A: Swift-XRT refined Analysis
- GRB 210413B: Swift-XRT observations
- GRB 210411C: Swift-XRT refined Analysis
- GRB 210410A: Swift-XRT refined Analysis
- GRB 210406A: Swift-XRT observations
- GRB 210402A: Swift-XRT refined Analysis
- GRB 210323A: Swift-XRT refined Analysis
- GRB 210321A: Swift-XRT refined Analysis
- GRB 210318A: Swift-XRT refined Analysis
- GRB210318B: Swift detection of a burst
- GRB 171205A: Continued ATCA observations
- GRB 210305A: Swift-XRT refined Analysis
- GRB 210307A: Swift-XRT refined Analysis
- GRB 210306A: Swift-XRT refined Analysis
- GRB 210226A: Swift-XRT refined Analysis
- GRB 210218A: Swift-XRT confirmation of afterglow
- GRB 210222B: Swift-XRT refined Analysis
- GRB 210218A: Swift/UVOT observations
- GRB 210218A: Swift-XRT observations
- GRB 210217A: Swift-XRT refined Analysis
- GRB 210212A: Swift-XRT refined Analysis
- GRB 210204A: observations with the 3.6m Devasthal Optical Telescope and possible jet break
- GRB 210211A: Swift-XRT refined Analysis
- Swift-XRT observations of IceCube-210210A
- GRB 210210A: Swift-XRT refined Analysis
- GRB 210209A: Swift-XRT refined Analysis
- GRB 210207B: Swift-XRT refined Analysis
- GRB 210204A / ZTF21aagwbjr: Swift-XRT observations
- GRB 210205A: Swift-XRT refined Analysis
- Continued Chandra observations of GW170817 at ~3.3 years since merger
- 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 201221D: near-infrared observation with LBT
- GRB 210112A: Swift-XRT refined Analysis
- Correction to GCN 29278: GRB 201216C XRT refined analysis
- GRB 201216C: Swift-XRT refined Analysis
- GRB 210102B: further Swift-XRT observations
- GW170817: HST observations at 3.4 years from merger
- GRB 210104A: Swift-XRT refined Analysis
- GRB 210104B: Swift-XRT refined Analysis
- GRB 210102B: Swift-XRT observations
- GRB 201227A: Swift-XRT observations
- GRB 201229A: Swift-XRT refined Analysis
- GRB 201223A: Swift-XRT refined Analysis
- Swift-XRT observations of Icecube 201222A
- Swift Trigger 1014012 (possible GRB 201221C) is likely not an astrophysical event
- GRB 201216A - further Swift-XRT observations
- GRB 201221D: Swift-XRT refined Analysis
- GRB 201221A: Swift-XRT refined Analysis
- GRB 201214A: Swift-XRT afterglow detection
- GRB 201216A: Swift-XRT observations
- Chandra observations of GW170817 at ~3.3 years since merger (Full report)
- GRB 201214B: Swift-XRT observations
- GRB 201214A: Swift-XRT observations
- Potential X-ray KN afterglow from Chandra observations of GW170817 ~3.3 years since merger (3 Epochs of 4)
- Long-lasting X-ray emission from GW170817 detected by Chandra
- Chandra observations of GW170817 at ~3.3 years since merger (Observation 1 of 4)
- GRB 201208A: Swift-XRT afterglow detection
- GRB 201209A: Swift-XRT refined Analysis
- Swift follow-up observations of the flat spectrum radio quasar PMN J0206-1150 in the error region of IceCube-201130A
- GRB 201203A: Swift-XRT afterglow detection
- GRB 201128B: Swift-XRT observations
- Swift observations of the Fermi-LAT source 4FGL J0206.4-1151 in the error region of IceCube-201130A