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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').
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"

28085 results found.

  1. GRB 260121A: 239Alferov CubeSat detection
  2. GRB 260131A: KAIT optical observations
  3. GRB 251230A: MeerLICHT afterglow detection
  4. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  5. GRB 260130A: Insight-HXMT/HE detection
  6. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  7. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  8. GRB 260127A: GECAM-B observation
  9. EP260131a: Liverpool Telescope optical upper limits
  10. EP260131a: COLIBRÍ further observations
  11. EP260131a: SVOM/VT optical observation
  12. EP260131a: Xinglong optical upper limit
  13. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  14. GRB 260131A/B: Fermi GBM Observation
  15. EP260131a: COLIBRÍ observations of slow optical fading
  16. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  17. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  18. GRB 260131B: MAXI/GSC detection
  19. EP260131a: COLIBRÍ optical observations of the counterpart
  20. EP260131a: Las Cumbres detection of an optical counterpart
  21. GRB 260127B: AstroSat CZTI detection
  22. GRB 260130A: Fermi GBM Detection
  23. EP260131a: Einstein Probe detection of an X-ray transient
  24. GRB 260127B: Fermi GBM Detection
  25. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  26. Fermi GRB 260130A: Global MASTER-Net observations report
  27. Fermi GRB 260129A: Global MASTER-Net observations report
  28. GRB 260128B: LCO optical upper limits
  29. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  30. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  31. GRB 260127A: Swift-BAT refined analysis
  32. GRB 260127B: Swift-XRT observations
  33. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  34. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  35. EP260128a: NOT optical counterpart candidate
  36. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  37. EP260128a: Liverpool Telescope optical observations and possible counterpart
  38. EP260128a: LCO optical upper limits
  39. EP260128a: Global MASTER-Net observations report
  40. EP260128a: Einstein Probe detection of an X-ray transient
  41. Fermi GRB 260127A: Global MASTER-Net observations report
  42. GRB 260127A: Fermi GBM Observation
  43. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  44. GRB 260127A: COLIBRÍ optical observations
  45. EP260126a: Seimei/TriCCS optical upper limit
  46. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  47. GRB 260127A: Swift-XRT refined Analysis
  48. GRB 260127A: SVOM/C-GFT optical observations
  49. GRB 260127A: Enhanced Swift-XRT position
  50. Fermi GRB 260127B: Global MASTER-Net observations report
  51. Swift GRB 260127A: Global MASTER-Net observations report
  52. GRB 260127A: LCO optical afterglow discovery
  53. GRB 260127A: Swift detection of a burst
  54. GRB 260125A: Swift-XRT observations
  55. EP260126a: Optical upper limit with Kinder observations
  56. EP260126a: Liverpool Telescope optical upper limits
  57. EP260126a: Further NOT optical upper limits
  58. EP260126a: COLIBRÍ optical upper limits
  59. EP260126a: NOT optical observations
  60. EP260126a: Einstein Probe detection of a fast X-ray transient
  61. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  62. GRB 251222A: SVOM/ECLAIRs refined analysis
  63. GRB 260125A: GOTO candidate optical counterpart
  64. Fermi GRB 260125B: Global MASTER-Net observations report
  65. GRB 260114A: SVOM/VT optical upper limits
  66. GRB 260122B: Swift-BAT refined analysis
  67. GRB 260120B: SVOM/GRM observation
  68. Swift GRB260122.97: Global MASTER-Net observations report
  69. EP260119a: Assy AZT-20 optical observations
  70. EP260119a: Mondy and SAO RAS optical upper limits
  71. EP260119a: Xinglong optical upper limit
  72. Fermi GRB 260120C: Global MASTER-Net observations report
  73. GRB 260120B: Swift-BAT refined analysis
  74. GRB 260120B: Swift-XRT refined Analysis
  75. EP260116a: COLIBRÍ further observations
  76. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  77. GRB 260120B: Fermi GBM Observation
  78. EP260105a: GTC/HiPERCAM optical observations
  79. GRB 260120B: Swift/UVOT Detection
  80. GRB 260120B: COLIBRÍ optical upper limits
  81. SVOM GRB260121.06: Global MASTER-Net observations report
  82. GRB 260120B: Enhanced Swift-XRT position
  83. GRB 260120B: SVOM/C-GFT optical counterpart detection
  84. GRB 260101A: 239Alferov CubeSat detection
  85. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  86. GRB 260120B: Swift detection of a burst
  87. Swift GRB260120B: Global MASTER-Net observations report
  88. EP260119A: Mondy I-Band Observations
  89. Fermi trigger No 790601190: Global MASTER-Net observations report
  90. Fermi trigger No 790570272: Global MASTER-Net observations report
  91. GRB 260114A: Swift/UVOT Upper Limits
  92. EP260119a: Liverpool Telescope optical follow-up observations
  93. GRB 251202A: further radio observations with the VLA
  94. EP260119a: KAIT optical observations
  95. EP260119a: SVOM/VT optical observation
  96. EP260119a: NOT optical observations
  97. EP260119a: SAO RAS optical observations
  98. SVOM GRB260119.92: Global MASTER-Net observations report
  99. SVOM GRB260119.92: Global MASTER-Net observations report
  100. SVOM GRB260119.90: Global MASTER-Net observations report

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