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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"

24365 results found.

  1. The EP-WXT trigger 01709260314 is likely a flaring star
  2. The EP-WXT trigger 01709260303 is likely a flaring star
  3. GRB 260417A: SVOM/GRM observation
  4. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  5. GRB 260419B: Fermi GBM Final Real-time Localization
  6. GRB 260419A: Fermi GBM Final Real-time Localization
  7. Fermi trigger No 798275385: Global MASTER-Net observations report
  8. EP260417a: GROWTH-India Telescope optical upper limit
  9. Fermi GRB 260417B: Global MASTER-Net observations report
  10. EP260417b: GROWTH-India Telescope optical upper limit
  11. EP260416a: Ondrejov D50 optical detection
  12. GRB 260418B: Fermi GBM Final Real-time Localization
  13. EP260417a: Global MASTER-Net observations report
  14. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  15. GRB 260418A: Fermi GBM Final Real-time Localization
  16. Fermi GRB 260417A: Global MASTER-Net observations report
  17. Konus-Wind detection of GRB 260411B
  18. GRB 260417B: Fermi GBM Final Real-time Localization
  19. IPN triangulation of GRB 260411B
  20. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  21. EP260417a: TRT optical counterpart detection
  22. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  23. EP260416a: KAIT optical upper limit
  24. GRB 260417A: Fermi GBM Final Real-time Localization
  25. EP260416a: SVOM/VT optical observation
  26. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  27. GRB 260411B: Glowbug gamma-ray detection
  28. EP260416a: Global MASTER-Net observations report
  29. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  30. GRB 260415B: NuSTAR detection of long prompt emission
  31. GRB 260415B: Fermi GBM Final Localization
  32. GRB 260415A: Fermi GBM Final Real-time Localization
  33. Fermi trigger No 797912738: Global MASTER-Net observations report
  34. GRB 260414A: Glowbug gamma-ray detection
  35. GRB 260414A: Fermi GBM Final Real-time Localization
  36. The EP-WXT trigger 01709260122 is likely a flaring star
  37. Fermi GRB 260413A: Global MASTER-Net observations report
  38. GRB 260413A: Fermi GBM Final Real-time Localization
  39. Konus-Wind detection of GRB 260410A (short/hard)
  40. EP260321a: SVOM/VT optical observations and color changes around peak
  41. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  42. The EP-WXT trigger 01709260010 is likely a flaring star
  43. Fermi GRB 260412A: Global MASTER-Net observations report
  44. GRB 260412A: Fermi GBM Observation
  45. GRB 260411B: Fermi-LAT detection
  46. GRB 260412A: SVOM detection of a long burst
  47. GRB 260412A: Fermi GBM Final Real-time Localization
  48. GRB 260410B: Fermi GBM Observation
  49. GRB 260411B: Ondrejov D50 optical afterglow detection
  50. GRB260411B: 3.6m DOT optical observation
  51. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  52. GRB 260411B: SVOM/GRM observation of a long burst
  53. GRB 260411B: Fermi GBM Detection
  54. GRB 260411B: GOTO optical counterpart candidate
  55. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  56. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  57. GRB 260411B: Fermi GBM Final Real-time Localization
  58. GRB 260411A: Fermi GBM Final Real-time Localization
  59. GRB 260410A: Fermi GBM Observation
  60. GRB 260410B: SVOM/GRM detection of a short faint burst
  61. The EP-WXT trigger 01709259790 is likely a flaring star
  62. GRB 260410B: Fermi GBM Final Real-time Localization
  63. EP-WXT01709259790: Xinglong optical upper limit
  64. GRB 260410A: Fermi-LAT detection
  65. GRB 260410A: Fermi GBM Final Real-time Localization
  66. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  67. EP260321a: Chandra X-ray Non-detection
  68. GRB 260409A: Fermi GBM Final Real-time Localization
  69. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  70. The EP-WXT trigger 01709259773 is likely a flaring star
  71. EP260409a: SVOM/VT optical upper limits
  72. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  73. EP260409a: Global MASTER-Net observations report
  74. GRB 260404A: Fermi GBM Final Localization
  75. GRB 260402A: SVOM/ECLAIRs refined analysis
  76. EP260402a / GRB 260402A: Mephisto optical upper limits
  77. EP-WXT01709259586: Xinglong optical upper limit
  78. EP260403a: Mephisto optical upper limits
  79. EP260402a/GRB 260402A: Xinglong optical upper limit
  80. GRB 260407A: Fermi GBM Final Real-time Localization
  81. EP260405a: SVOM/VT optical upper limits
  82. EP260405a: Global MASTER-Net observations report
  83. EP260405a: Einstein Probe detection of a fast X-ray transient
  84. The EP-WXT trigger 01709259621 is likely a flaring star
  85. The EP-WXT trigger 01709259615 is likely a flaring star
  86. Fermi trigger No 797039833: Global MASTER-Net observations report
  87. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  88. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  89. The EP-WXT trigger 01709259586 is likely a flaring star
  90. GRB 260330B: SVOM/VT further optical observation
  91. GRB 260330B: SVOM/ECLAIRs refined analysis
  92. GRB 260330B: SVOM/VT optical candidate
  93. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  94. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  95. GRB 260402C: NuSTAR detection of prompt emission
  96. EP260324A / AT 2026hir: COLIBRÍ optical observations
  97. GRB 260403A: Fermi GBM Final Real-time Localization
  98. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  99. GRB 260402B: Fermi GBM Final Real-time Localization
  100. GRB260402A: GROWTH-India Telescope optical upper limit

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