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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"

21770 results found.

  1. GRB260131A/B: 3.6m DOT Optical Observations
  2. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  3. GRB 260211A: SVOM detection of a burst
  4. Konus-Wind detection of GRB 260209B
  5. Konus-Wind detection of GRB 260127B
  6. EP260209a: COLIBRÍ optical upper limit
  7. EP260209a: LCO optical upper limits
  8. EP260210a: refined analysis of the EP-FXT observation
  9. GRB 260208A: LCO detection of the optical counterpart
  10. EP260209a: Einstein Probe detection of a fast X-ray transient
  11. EP260210a: Optical upper limits with Kinder observations
  12. GRB 260210A: AstroSat CZTI detection
  13. EP260210a: COLIBRÍ optical upper limit
  14. EP260210a: SVOM/C-GFT upper limit
  15. EP260210a: Einstein Probe detection of an X-ray transient
  16. GRB 260208C: SVOM/GRM observation
  17. GRB 260204A: Swift-XRT afterglow detection
  18. GRB 260208B: AstroSat CZTI detection of a bright long burst
  19. GRB260208A: Liverpool Telescope optical follow-up observations
  20. GRB 260208A: NuSTAR detection of prompt emission
  21. Fermi GRB 260209A: Global MASTER-Net observations report
  22. GRB 260131A/B: continued Mondy optical observations
  23. GRB 260204A: Swift/UVOT Upper Limits
  24. GRB 260208B: COLIBRÍ optical observations
  25. GRB 260208A: Mondy optical observations
  26. GRB 260208A: 1.3m DFOT optical detection
  27. GRB 260208A: COLIBRÍ optical observations
  28. GRB 260208A: Liverpool Telescope optical detection
  29. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  30. GRB 260208A: SVOM/VT optical observation
  31. GRB 260208B: SVOM/GRM observation of a bright burst
  32. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  33. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  34. GRB 260131A/B: Mondy and Terskol optical observations
  35. GRB 260206A: Swift-XRT observations
  36. GRB 260204A: LCO optical afterglow detection
  37. GRB 260204A: SVOM/VT optical candidate
  38. GRB 260204A: GOTO optical upper limit
  39. GRB 260204A: LCO optical upper limits
  40. EP260110a: Late GTC/EMIR near-infrared observations
  41. GRB 260204A: SVOM detection of a burst
  42. Konus-Wind detection of GRB 260121A
  43. GRB 260131A: KAIT optical observations
  44. GRB 251230A: MeerLICHT afterglow detection
  45. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  46. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  47. EP260131a: Liverpool Telescope optical upper limits
  48. EP260131a: COLIBRÍ further observations
  49. Konus-Wind detection of GRB 260131A/B
  50. EP260131a: SVOM/VT optical observation
  51. EP260131a: Xinglong optical upper limit
  52. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  53. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  54. EP260131a: COLIBRÍ observations of slow optical fading
  55. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  56. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  57. EP260131a: COLIBRÍ optical observations of the counterpart
  58. EP260131a: Einstein Probe detection of an X-ray transient
  59. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  60. GRB 260128B: LCO optical upper limits
  61. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  62. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  63. GRB 260127A: Swift-BAT refined analysis
  64. GRB 260127B: Swift-XRT observations
  65. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  66. EP260128a: NOT optical counterpart candidate
  67. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  68. EP260128a: Liverpool Telescope optical observations and possible counterpart
  69. EP260128a: LCO optical upper limits
  70. EP260128a: Einstein Probe detection of an X-ray transient
  71. GRB 260127A: COLIBRÍ optical observations
  72. EP260126a: Seimei/TriCCS optical upper limit
  73. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  74. GRB 260127B: GOTO candidate optical counterpart
  75. GRB 260127A: SVOM/C-GFT optical observations
  76. GRB 260127A: Enhanced Swift-XRT position
  77. GRB 260127A: LCO optical afterglow discovery
  78. GRB 260127A: Swift detection of a burst
  79. GRB 260125A: Swift-XRT observations
  80. EP260126a: Optical upper limit with Kinder observations
  81. EP260126a: Liverpool Telescope optical upper limits
  82. EP260126a: Further NOT optical upper limits
  83. EP260126a: COLIBRÍ optical upper limits
  84. EP260126a: NOT optical observations
  85. EP260126a: Einstein Probe detection of a fast X-ray transient
  86. GRB 251222A: SVOM/ECLAIRs refined analysis
  87. GRB 260125A: GOTO candidate optical counterpart
  88. GRB 260114A: SVOM/VT optical upper limits
  89. GRB 260120A: AstroSat CZTI detection
  90. GRB 260120B: SVOM/GRM observation
  91. EP260119a: Assy AZT-20 optical observations
  92. EP260119a: Mondy and SAO RAS optical upper limits
  93. EP260119a: Xinglong optical upper limit
  94. EP260116a: COLIBRÍ further observations
  95. EP260105a: GTC/HiPERCAM optical observations
  96. GRB 260120B: Swift/UVOT Detection
  97. GRB 260120B: COLIBRÍ optical upper limits
  98. GRB 260120B: Enhanced Swift-XRT position
  99. GRB 260120B: SVOM/C-GFT optical counterpart detection
  100. EP260116a: COLIBRÍ observations of a tentative optical rebrightening

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