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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"

3388 results found.

  1. GRB 260818B: Further EP-FXT observation
  2. GRB 260807A: EP-FXT follow-up observations
  3. GRB 260822A: EP/FXT follow-up observations
  4. GRB 260818B: EP-FXT follow-up observation
  5. GRB260818A: EP-FXT follow-up observation
  6. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  7. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  8. AT 2026wki: EP/FXT follow-up observations
  9. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  10. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  11. EP260728a: EP-FXT follow-up observation
  12. GRB 260726A: EP-FXT follow-up observations
  13. GRB 260727A: EP/FXT follow-up observations
  14. EP260723a: further EP-FXT follow-up observation
  15. EP260725a: EP-WXT detection of an X-ray transient
  16. EP260723a: EP-FXT follow-up observation
  17. GRB 260718A: EP-FXT follow-up observation
  18. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  19. GRB 260618B: EP-FXT follow-up observation upper limit
  20. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  21. EP260711a: EP-FXT follow-up observation
  22. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  23. GRB 260706A: Further EP-FXT follow-up observation
  24. GRB 260706A: EP-FXT follow-up observation
  25. GRB 260704A: EP-FXT follow-up observation
  26. EP260703a: EP-FXT follow-up observation
  27. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  28. EP260628a: EP-FXT follow-up observation
  29. EP260626a: EP-FXT follow-up observation
  30. GRB 260614B: EP-FXT follow-up observation
  31. EP260618a: EP-FXT follow-up observation
  32. EP260618a: EP-WXT detection of an X-ray transient
  33. EP260616a/GRB 260616B: EP-FXT follow-up observation
  34. IceCube-260610A: EP-FXT follow-up observation
  35. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  36. EP260605a: EP-FXT follow-up observation
  37. GRB 260607B: Fermi-LAT detection
  38. EP260602d: EP-FXT follow-up observation
  39. EP260602c: EP-FXT follow-up observation
  40. EP260602a: EP-FXT follow-up observation
  41. GRB 260603A: EP-FXT follow-up observation
  42. EP260601a/GRB 260601B: EP-FXT follow-up observation
  43. EP260602b: EP-FXT follow-up observation
  44. AT2026nik: EP-FXT X-ray counterpart
  45. EP260527a/GRB 260527A: EP-FXT follow-up observation
  46. EP260526a: EP-FXT follow-up observation
  47. Fermi GRB 260516C: Global MASTER-Net observations report
  48. GRB 260515A: EP-FXT follow-up observation
  49. EP260514a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  50. SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
  51. EP260512a: EP-FXT follow-up observation
  52. GRB 260511B: EP-FXT follow-up observation
  53. GRB 260510B: EP-FXT follow-up observation
  54. SVOM GRB 260509A: MASTER-OAFA optical observation
  55. SVOM GRB 260504B: MASTER-OAFA optical observations
  56. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  57. GRB 260310A: Late-time Chandra X-ray Detection
  58. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  59. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  60. GOTO26djh/AT2026jpw : MASTER OT observation
  61. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  62. GRB 260411B: Fermi GBM Detection
  63. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  64. EP260321a: Chandra X-ray Non-detection
  65. EP260405a: Global MASTER-Net observations report
  66. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  67. GRB 260402A: MASTER optical observations
  68. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  69. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  70. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  71. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  72. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  73. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  74. GRB 260226A: Fermi-LAT refined analysis
  75. EP260223a: EP-FXT follow-up observation
  76. EP260214b: EP-FXT follow-up observation
  77. EP260214a: refined analysis of the EP-FXT observation
  78. EP260213a: refined analysis of the EP-FXT observation
  79. GRB 260208A: Swift UVOT detection
  80. EP260210a: refined analysis of the EP-FXT observation
  81. GRB 260208B: refined analysis of the EP-FXT observation
  82. GRB 260204A: Swift-XRT afterglow detection
  83. GRB 260208B: Swift-XRT observations
  84. GRB 260204A: Swift/UVOT Upper Limits
  85. GRB 260208A: Swift-XRT observations
  86. GRB 260208B: Fermi-LAT detection
  87. GRB 260206A: Swift-XRT observations
  88. GRB 260204A: Swift-XRT observations
  89. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  90. GRB 260127B: Swift-XRT observations
  91. GRB 260127A: Swift-XRT refined Analysis
  92. GRB 260127A: Prompt enhanced Swift-XRT position
  93. GRB 260125A: Swift-XRT observations
  94. EP260126a: EP-FXT follow-up observation
  95. GRB 260120B: Swift-XRT refined Analysis
  96. EP260119a: update of EP-FXT follow-up observation
  97. GRB 260117A: Swift-XRT afterglow detection
  98. Swift GRB260118.48: Global MASTER-Net observations report
  99. GRB 260117A: Swift-XRT observations
  100. GRB 260114A: VLT/HAWK-I near-infrared upper limits

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