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"
3038 results found.
- GRB 200630A: Swift-XRT refined Analysis
- GRB 200623A: Swift XRT further observations
- GRB 200623A: Swift-XRT observations
- Swift-XRT observations of IceCube 200615A
- Fermi GRB 200616A: Global MASTER-Net observations report
- GRB 200613A: Swift-XRT afterglow detection
- GRB 200613A: Fermi-LAT detection
- GRB 200612A: Swift-XRT refined Analysis
- GRB 200529A: Swift-XRT refined Analysis
- GRB 200528A: Swift-XRT refined Analysis
- GRB 200528A: Swift/UVOT Upper Limits
- GRB 200524A: Swift-XRT afterglow detection
- GRB 200522A: Swift-XRT refined Analysis
- GRB 200517A: Swift-XRT Confirmation of afterglow
- GRB 200519A: Swift-XRT refined Analysis
- GRB 200517A: Swift-XRT afterglow detection
- GRB 200512A: Swift-XRT refined Analysis
- GRB 200509A: Swift-XRT refined Analysis
- GRB 200424A: Swift-XRT afterglow detection
- SGR 1935+2154 the Insight-HXMT observation plan
- GRB 200424A: Swift/UVOT Upper Limits
- GRB 200425A: Swift-XRT refined Analysis
- GRB 200424A: Swift-XRT observations
- GRB 200412B: Swift XRT confirmation of afterglow and UVOT upper limits
- GRB 200405B: Further Swift-XRT observations
- GRB 200412B: Swift-XRT afterglow detection
- GRB 200411A: Swift-XRT refined Analysis
- LIGO/Virgo S200225q: Swift XRT observations, 1 X-ray sources
- LIGO/Virgo S200224ca: Swift XRT observations, 8 X-ray sources
- GRB 200410A: Swift-XRT refined Analysis
- GRB 200409A: Swift-XRT refined Analysis
- GRB 200405B: Swift-XRT observations
- GRB 200325B: further Swift-XRT observations
- GRB 200325B: Swift-XRT and UVOT observations
- GRB 200324A: Swift-XRT refined Analysis
- Chandra observations of GW170817 at 2.5 years since merger (All epochs 4 of 4)
- GW170817: Continued X-ray emission detected with Chandra at 940 days post-merger
- LIGO/Virgo S200316bj: No counterpart candidates in Fermi-LAT observations
- LIGO/Virgo S200213t: Continued Swift UVOT and XRT observations of ZTF20aamvmzj (AT2020cja)
- LIGO/Virgo S200311bg: No significant counterpart candidates in Fermi-LAT observations
- Chandra observations of GW170817 ~ 2.5 years since merger (epoch 1 of 4)
- GRB 200306C: Swift-XRT refined Analysis
- GRB 200306A: Swift-XRT refined Analysis
- GRB 200303A: Swift-XRT refined Analysis
- LIGO/Virgo S200302c: No significant counterpart candidates in Fermi-LAT observations
- GRB 200228B: Swift-XRT refined Analysis
- GRB 200227A: Swift-XRT refined Analysis
- LIGO/Virgo S200225q: No counterpart candidates in Fermi-LAT observations
- LIGO/Virgo S200224ca: No counterpart candidates in Fermi-LAT observations
- GRB 200219C: Swift-XRT afterglow confirmation
- GRB 200224A: Swift-XRT refined Analysis
- GRB 200219C: Swift-XRT afterglow detection
- LIGO/Virgo S200213t: Swift UVOT and XRT observations of ZTF20aamvmzj (AT2020cja)
- LIGO/Virgo S200219ac: No counterpart candidates in Fermi-LAT observations
- GRB 200219A: Swift-XRT refined Analysis correction
- GRB 200219A: Swift-XRT refined Analysis
- GRB 200216B: Swift-XRT refined Analysis
- Further Swift-XRT observations of Swift J0840.7-3516
- GRB 200215A: Swift-XRT refined Analysis
- LIGO/Virgo S200213t: No candidates found in J-GEM follow-up observations
- LIGO/Virgo S200213t: No counterpart candidates in Fermi-LAT observations
- LIGO/Virgo S200208q: No counterpart candidates in Fermi-LAT observations
- GRB 200205B: ESO/NTT near-infrared imaging
- GRB 200205B: Swift-XRT refined Analysis
- GRB 200131A: Swift-XRT refined Analysis
- LIGO/Virgo S200129m: No counterpart candidates in Fermi-LAT observations
- LIGO/Virgo S200128d: No counterpart candidates in Fermi-LAT observations
- GRB 200127A: Swift-XRT refined Analysis
- GRB 200125A: Further Swift-XRT observations
- GRB 200125A: TNG detection of a NIR counterpart candidate
- Correction to GRB 200125A: Swift-XRT refined analysis
- GRB 200125A: Swift-XRT refined Analysis
- LIGO/Virgo S200115j: Further Swift-XRT sources
- GRB 200122A: Swift-XRT refined Analysis
- GRB 191031D: XMM-Newton upper limit
- LIGO/Virgo S200115j: NIR upper limits for ZTF20aafqvyc/AT2020yq from the Palomar 200-inch telescope
- LIGO/Virgo S200114f: No transients found in J-GEM observations of nearby galaxies
- LIGO/Virgo S200115j: Swift-XRT sources
- LIGO/Virgo S200114f: Swift-XRT sources and observations
- LIGO/Virgo S200115j: No counterpart candidates in Fermi-LAT observations
- LIGO/Virgo S200114f: No counterpart candidates in Fermi-LAT observations
- LIGO/Virgo 200112r: No counterpart candidates in Fermi-LAT observations
- GRB 200107B: Swift-XRT refined Analysis
- GRB 200109A: Swift-XRT refined Analysis
- LIGO/Virgo 200105ae: No counterpart candidates in Fermi-LAT observations
- Fermi trigger No 599954133: Global MASTER-Net observations report
- GRB 191228A: Swift-XRT refined Analysis
- GRB 191227A: Marginal detection by Fermi-LAT
- GRB 191221B: Swift-XRT refined Analysis
- LIGO/Virgo S191222n: No counterpart candidates in Fermi-LAT observations
- GRB 191220A: Swift-XRT refined Analysis
- LIGO/Virgo S191213g: Swift UVOT/XRT observations of Pan-STARRS1 candidate: PS19hgw
- LIGO/Virgo S191216ap: No candidates found in J-GEM follow-up observations of HAWC error region
- LIGO/Virgo S191213g: No candidates found in J-GEM follow-up observations
- LIGO/Virgo S191216ap and IceCube neutrino: Swift XRT sources
- LIGO/Virgo S191213g: Swift UVOT/XRT observations of three ZTF sources
- LIGO/Virgo G191216ap: No counterpart candidates in Fermi-LAT observations
- LIGO/Virgo S191215w: No counterpart candidates in Fermi-LAT observations
- LIGO/Virgo S191213g: No counterpart candidates in Fermi-LAT observations
- Possible HAWC-detected GRB 191210A: Fermi-LAT Upper Limits