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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"

28089 results found.

  1. GRB 260204A : MASTER Global robotic net optical observations
  2. Fermi GBM Sub-Threshold Detection of GRB 260204A
  3. GRB 260204A: LCO optical upper limits
  4. EP260110a: Late GTC/EMIR near-infrared observations
  5. GRB 260121A: 239Alferov CubeSat detection
  6. GRB 260131A: KAIT optical observations
  7. GRB 251230A: MeerLICHT afterglow detection
  8. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  9. GRB 260130A: Insight-HXMT/HE detection
  10. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  11. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  12. GRB 260127A: GECAM-B observation
  13. EP260131a: Liverpool Telescope optical upper limits
  14. EP260131a: COLIBRÍ further observations
  15. EP260131a: SVOM/VT optical observation
  16. EP260131a: Xinglong optical upper limit
  17. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  18. GRB 260131A/B: Fermi GBM Observation
  19. EP260131a: COLIBRÍ observations of slow optical fading
  20. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  21. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  22. GRB 260131B: MAXI/GSC detection
  23. EP260131a: COLIBRÍ optical observations of the counterpart
  24. EP260131a: Las Cumbres detection of an optical counterpart
  25. GRB 260127B: AstroSat CZTI detection
  26. GRB 260130A: Fermi GBM Detection
  27. EP260131a: Einstein Probe detection of an X-ray transient
  28. GRB 260127B: Fermi GBM Detection
  29. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  30. Fermi GRB 260130A: Global MASTER-Net observations report
  31. Fermi GRB 260129A: Global MASTER-Net observations report
  32. GRB 260128B: LCO optical upper limits
  33. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  34. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  35. GRB 260127A: Swift-BAT refined analysis
  36. GRB 260127B: Swift-XRT observations
  37. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  38. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  39. EP260128a: NOT optical counterpart candidate
  40. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  41. EP260128a: Liverpool Telescope optical observations and possible counterpart
  42. EP260128a: LCO optical upper limits
  43. EP260128a: Global MASTER-Net observations report
  44. EP260128a: Einstein Probe detection of an X-ray transient
  45. Fermi GRB 260127A: Global MASTER-Net observations report
  46. GRB 260127A: Fermi GBM Observation
  47. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  48. GRB 260127A: COLIBRÍ optical observations
  49. EP260126a: Seimei/TriCCS optical upper limit
  50. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  51. GRB 260127A: Swift-XRT refined Analysis
  52. GRB 260127A: SVOM/C-GFT optical observations
  53. GRB 260127A: Enhanced Swift-XRT position
  54. Fermi GRB 260127B: Global MASTER-Net observations report
  55. Swift GRB 260127A: Global MASTER-Net observations report
  56. GRB 260127A: LCO optical afterglow discovery
  57. GRB 260127A: Swift detection of a burst
  58. GRB 260125A: Swift-XRT observations
  59. EP260126a: Optical upper limit with Kinder observations
  60. EP260126a: Liverpool Telescope optical upper limits
  61. EP260126a: Further NOT optical upper limits
  62. EP260126a: COLIBRÍ optical upper limits
  63. EP260126a: NOT optical observations
  64. EP260126a: Einstein Probe detection of a fast X-ray transient
  65. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  66. GRB 251222A: SVOM/ECLAIRs refined analysis
  67. GRB 260125A: GOTO candidate optical counterpart
  68. Fermi GRB 260125B: Global MASTER-Net observations report
  69. GRB 260114A: SVOM/VT optical upper limits
  70. GRB 260122B: Swift-BAT refined analysis
  71. GRB 260120B: SVOM/GRM observation
  72. Swift GRB260122.97: Global MASTER-Net observations report
  73. EP260119a: Assy AZT-20 optical observations
  74. EP260119a: Mondy and SAO RAS optical upper limits
  75. EP260119a: Xinglong optical upper limit
  76. Fermi GRB 260120C: Global MASTER-Net observations report
  77. GRB 260120B: Swift-BAT refined analysis
  78. GRB 260120B: Swift-XRT refined Analysis
  79. EP260116a: COLIBRÍ further observations
  80. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  81. GRB 260120B: Fermi GBM Observation
  82. EP260105a: GTC/HiPERCAM optical observations
  83. GRB 260120B: Swift/UVOT Detection
  84. GRB 260120B: COLIBRÍ optical upper limits
  85. SVOM GRB260121.06: Global MASTER-Net observations report
  86. GRB 260120B: Enhanced Swift-XRT position
  87. GRB 260120B: SVOM/C-GFT optical counterpart detection
  88. GRB 260101A: 239Alferov CubeSat detection
  89. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  90. GRB 260120B: Swift detection of a burst
  91. Swift GRB260120B: Global MASTER-Net observations report
  92. EP260119A: Mondy I-Band Observations
  93. Fermi trigger No 790601190: Global MASTER-Net observations report
  94. Fermi trigger No 790570272: Global MASTER-Net observations report
  95. GRB 260114A: Swift/UVOT Upper Limits
  96. EP260119a: Liverpool Telescope optical follow-up observations
  97. GRB 251202A: further radio observations with the VLA
  98. EP260119a: KAIT optical observations
  99. EP260119a: SVOM/VT optical observation
  100. EP260119a: NOT optical observations

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