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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').
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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"

24361 results found.

  1. GRB 260419B: Fermi GBM Final Real-time Localization
  2. GRB 260419A: Fermi GBM Final Real-time Localization
  3. Fermi trigger No 798275385: Global MASTER-Net observations report
  4. EP260417a: GROWTH-India Telescope optical upper limit
  5. Fermi GRB 260417B: Global MASTER-Net observations report
  6. EP260417b: GROWTH-India Telescope optical upper limit
  7. EP260416a: Ondrejov D50 optical detection
  8. GRB 260418B: Fermi GBM Final Real-time Localization
  9. EP260417a: Global MASTER-Net observations report
  10. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  11. GRB 260418A: Fermi GBM Final Real-time Localization
  12. Fermi GRB 260417A: Global MASTER-Net observations report
  13. Konus-Wind detection of GRB 260411B
  14. GRB 260417B: Fermi GBM Final Real-time Localization
  15. IPN triangulation of GRB 260411B
  16. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  17. EP260417a: TRT optical counterpart detection
  18. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  19. EP260416a: KAIT optical upper limit
  20. GRB 260417A: Fermi GBM Final Real-time Localization
  21. EP260416a: SVOM/VT optical observation
  22. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  23. GRB 260411B: Glowbug gamma-ray detection
  24. EP260416a: Global MASTER-Net observations report
  25. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  26. GRB 260415B: NuSTAR detection of long prompt emission
  27. GRB 260415B: Fermi GBM Final Localization
  28. GRB 260415A: Fermi GBM Final Real-time Localization
  29. Fermi trigger No 797912738: Global MASTER-Net observations report
  30. GRB 260414A: Glowbug gamma-ray detection
  31. GRB 260414A: Fermi GBM Final Real-time Localization
  32. The EP-WXT trigger 01709260122 is likely a flaring star
  33. Fermi GRB 260413A: Global MASTER-Net observations report
  34. GRB 260413A: Fermi GBM Final Real-time Localization
  35. Konus-Wind detection of GRB 260410A (short/hard)
  36. EP260321a: SVOM/VT optical observations and color changes around peak
  37. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  38. The EP-WXT trigger 01709260010 is likely a flaring star
  39. Fermi GRB 260412A: Global MASTER-Net observations report
  40. GRB 260412A: Fermi GBM Observation
  41. GRB 260411B: Fermi-LAT detection
  42. GRB 260412A: SVOM detection of a long burst
  43. GRB 260412A: Fermi GBM Final Real-time Localization
  44. GRB 260410B: Fermi GBM Observation
  45. GRB 260411B: Ondrejov D50 optical afterglow detection
  46. GRB260411B: 3.6m DOT optical observation
  47. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  48. GRB 260411B: SVOM/GRM observation of a long burst
  49. GRB 260411B: Fermi GBM Detection
  50. GRB 260411B: GOTO optical counterpart candidate
  51. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  52. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  53. GRB 260411B: Fermi GBM Final Real-time Localization
  54. GRB 260411A: Fermi GBM Final Real-time Localization
  55. GRB 260410A: Fermi GBM Observation
  56. GRB 260410B: SVOM/GRM detection of a short faint burst
  57. The EP-WXT trigger 01709259790 is likely a flaring star
  58. GRB 260410B: Fermi GBM Final Real-time Localization
  59. EP-WXT01709259790: Xinglong optical upper limit
  60. GRB 260410A: Fermi-LAT detection
  61. GRB 260410A: Fermi GBM Final Real-time Localization
  62. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  63. EP260321a: Chandra X-ray Non-detection
  64. GRB 260409A: Fermi GBM Final Real-time Localization
  65. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  66. The EP-WXT trigger 01709259773 is likely a flaring star
  67. EP260409a: SVOM/VT optical upper limits
  68. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  69. EP260409a: Global MASTER-Net observations report
  70. GRB 260404A: Fermi GBM Final Localization
  71. GRB 260402A: SVOM/ECLAIRs refined analysis
  72. EP260402a / GRB 260402A: Mephisto optical upper limits
  73. EP-WXT01709259586: Xinglong optical upper limit
  74. EP260403a: Mephisto optical upper limits
  75. EP260402a/GRB 260402A: Xinglong optical upper limit
  76. GRB 260407A: Fermi GBM Final Real-time Localization
  77. EP260405a: SVOM/VT optical upper limits
  78. EP260405a: Global MASTER-Net observations report
  79. EP260405a: Einstein Probe detection of a fast X-ray transient
  80. The EP-WXT trigger 01709259621 is likely a flaring star
  81. The EP-WXT trigger 01709259615 is likely a flaring star
  82. Fermi trigger No 797039833: Global MASTER-Net observations report
  83. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  84. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  85. The EP-WXT trigger 01709259586 is likely a flaring star
  86. GRB 260330B: SVOM/VT further optical observation
  87. GRB 260330B: SVOM/ECLAIRs refined analysis
  88. GRB 260330B: SVOM/VT optical candidate
  89. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  90. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  91. GRB 260402C: NuSTAR detection of prompt emission
  92. EP260324A / AT 2026hir: COLIBRÍ optical observations
  93. GRB 260403A: Fermi GBM Final Real-time Localization
  94. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  95. GRB 260402B: Fermi GBM Final Real-time Localization
  96. GRB260402A: GROWTH-India Telescope optical upper limit
  97. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  98. GRB 260401A: SVOM/GRM observation
  99. GRB 260401A: GECAM-B observation
  100. GRB 260402A: MASTER optical observations

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