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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"

24249 results found.

  1. Konus-Wind detection of GRB 260411B
  2. GRB 260417B: Fermi GBM Final Real-time Localization
  3. IPN triangulation of GRB 260411B
  4. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  5. EP260417a: TRT optical counterpart detection
  6. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  7. EP260416a: KAIT optical upper limit
  8. GRB 260417A: Fermi GBM Final Real-time Localization
  9. EP260416a: SVOM/VT optical observation
  10. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  11. GRB 260411B: Glowbug gamma-ray detection
  12. EP260416a: Global MASTER-Net observations report
  13. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  14. GRB 260415B: NuSTAR detection of long prompt emission
  15. GRB 260415B: Fermi GBM Final Localization
  16. GRB 260415A: Fermi GBM Final Real-time Localization
  17. Fermi trigger No 797912738: Global MASTER-Net observations report
  18. GRB 260414A: Glowbug gamma-ray detection
  19. GRB 260414A: Fermi GBM Final Real-time Localization
  20. The EP-WXT trigger 01709260122 is likely a flaring star
  21. Fermi GRB 260413A: Global MASTER-Net observations report
  22. GRB 260413A: Fermi GBM Final Real-time Localization
  23. Konus-Wind detection of GRB 260410A (short/hard)
  24. EP260321a: SVOM/VT optical observations and color changes around peak
  25. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  26. The EP-WXT trigger 01709260010 is likely a flaring star
  27. Fermi GRB 260412A: Global MASTER-Net observations report
  28. GRB 260412A: Fermi GBM Observation
  29. GRB 260411B: Fermi-LAT detection
  30. GRB 260412A: SVOM detection of a long burst
  31. GRB 260412A: Fermi GBM Final Real-time Localization
  32. GRB 260410B: Fermi GBM Observation
  33. GRB 260411B: Ondrejov D50 optical afterglow detection
  34. GRB260411B: 3.6m DOT optical observation
  35. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  36. GRB 260411B: SVOM/GRM observation of a long burst
  37. GRB 260411B: Fermi GBM Detection
  38. GRB 260411B: GOTO optical counterpart candidate
  39. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  40. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  41. GRB 260411B: Fermi GBM Final Real-time Localization
  42. GRB 260411A: Fermi GBM Final Real-time Localization
  43. GRB 260410A: Fermi GBM Observation
  44. GRB 260410B: SVOM/GRM detection of a short faint burst
  45. The EP-WXT trigger 01709259790 is likely a flaring star
  46. GRB 260410B: Fermi GBM Final Real-time Localization
  47. EP-WXT01709259790: Xinglong optical upper limit
  48. GRB 260410A: Fermi-LAT detection
  49. GRB 260410A: Fermi GBM Final Real-time Localization
  50. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  51. EP260321a: Chandra X-ray Non-detection
  52. GRB 260409A: Fermi GBM Final Real-time Localization
  53. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  54. The EP-WXT trigger 01709259773 is likely a flaring star
  55. EP260409a: SVOM/VT optical upper limits
  56. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  57. EP260409a: Global MASTER-Net observations report
  58. GRB 260404A: Fermi GBM Final Localization
  59. GRB 260402A: SVOM/ECLAIRs refined analysis
  60. EP260402a / GRB 260402A: Mephisto optical upper limits
  61. EP-WXT01709259586: Xinglong optical upper limit
  62. EP260403a: Mephisto optical upper limits
  63. EP260402a/GRB 260402A: Xinglong optical upper limit
  64. GRB 260407A: Fermi GBM Final Real-time Localization
  65. EP260405a: SVOM/VT optical upper limits
  66. EP260405a: Global MASTER-Net observations report
  67. EP260405a: Einstein Probe detection of a fast X-ray transient
  68. The EP-WXT trigger 01709259621 is likely a flaring star
  69. The EP-WXT trigger 01709259615 is likely a flaring star
  70. Fermi trigger No 797039833: Global MASTER-Net observations report
  71. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  72. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  73. The EP-WXT trigger 01709259586 is likely a flaring star
  74. GRB 260330B: SVOM/VT further optical observation
  75. GRB 260330B: SVOM/ECLAIRs refined analysis
  76. GRB 260330B: SVOM/VT optical candidate
  77. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  78. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  79. GRB 260402C: NuSTAR detection of prompt emission
  80. EP260324A / AT 2026hir: COLIBRÍ optical observations
  81. GRB 260403A: Fermi GBM Final Real-time Localization
  82. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  83. GRB 260402B: Fermi GBM Final Real-time Localization
  84. GRB260402A: GROWTH-India Telescope optical upper limit
  85. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  86. GRB 260401A: SVOM/GRM observation
  87. GRB 260401A: GECAM-B observation
  88. GRB 260402A: MASTER optical observations
  89. GRB 260402A: SVOM detection of a burst
  90. Fermi GRB 260401A: Global MASTER-Net observations report
  91. GRB 260401A: Fermi GBM Observation
  92. GRB 260401A: NuSTAR detection of prompt emission
  93. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  94. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  95. GRB 260401A: Fermi GBM Final Real-time Localization
  96. EP260321a :Xinglong optical observations
  97. EP260327a: Xinglong optical upper limit
  98. EP260329b: GOTO detection of optical counterpart
  99. GRB 260330B: SVOM/VT optical upper limits
  100. Konus-Wind detection of GRB 260320A

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