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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"

23630 results found.

  1. The EP-WXT trigger 01709260122 is likely a flaring star
  2. Fermi GRB 260413A: Global MASTER-Net observations report
  3. GRB 260413A: Fermi GBM Final Real-time Localization
  4. Konus-Wind detection of GRB 260410A (short/hard)
  5. EP260321a: SVOM/VT optical observations and color changes around peak
  6. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  7. The EP-WXT trigger 01709260010 is likely a flaring star
  8. Fermi GRB 260412A: Global MASTER-Net observations report
  9. GRB 260412A: Fermi GBM Observation
  10. GRB 260411B: Fermi-LAT detection
  11. GRB 260412A: SVOM detection of a long burst
  12. GRB 260412A: Fermi GBM Final Real-time Localization
  13. GRB 260410B: Fermi GBM Observation
  14. GRB 260411B: Ondrejov D50 optical afterglow detection
  15. GRB260411B: 3.6m DOT optical observation
  16. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  17. GRB 260411B: SVOM/GRM observation of a long burst
  18. GRB 260411B: Fermi GBM Detection
  19. GRB 260411B: GOTO optical counterpart candidate
  20. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  21. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  22. GRB 260411B: Fermi GBM Final Real-time Localization
  23. GRB 260411A: Fermi GBM Final Real-time Localization
  24. GRB 260410A: Fermi GBM Observation
  25. GRB 260410B: SVOM/GRM detection of a short faint burst
  26. The EP-WXT trigger 01709259790 is likely a flaring star
  27. GRB 260410B: Fermi GBM Final Real-time Localization
  28. EP-WXT01709259790: Xinglong optical upper limit
  29. GRB 260410A: Fermi-LAT detection
  30. GRB 260410A: Fermi GBM Final Real-time Localization
  31. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  32. EP260321a: Chandra X-ray Non-detection
  33. GRB 260409A: Fermi GBM Final Real-time Localization
  34. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  35. The EP-WXT trigger 01709259773 is likely a flaring star
  36. EP260409a: SVOM/VT optical upper limits
  37. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  38. EP260409a: Global MASTER-Net observations report
  39. GRB 260404A: Fermi GBM Final Localization
  40. GRB 260402A: SVOM/ECLAIRs refined analysis
  41. EP260402a / GRB 260402A: Mephisto optical upper limits
  42. EP-WXT01709259586: Xinglong optical upper limit
  43. EP260403a: Mephisto optical upper limits
  44. EP260402a/GRB 260402A: Xinglong optical upper limit
  45. GRB 260407A: Fermi GBM Final Real-time Localization
  46. EP260405a: SVOM/VT optical upper limits
  47. EP260405a: Global MASTER-Net observations report
  48. EP260405a: Einstein Probe detection of a fast X-ray transient
  49. The EP-WXT trigger 01709259621 is likely a flaring star
  50. The EP-WXT trigger 01709259615 is likely a flaring star
  51. Fermi trigger No 797039833: Global MASTER-Net observations report
  52. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  53. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  54. The EP-WXT trigger 01709259586 is likely a flaring star
  55. GRB 260330B: SVOM/VT further optical observation
  56. GRB 260330B: SVOM/ECLAIRs refined analysis
  57. GRB 260330B: SVOM/VT optical candidate
  58. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  59. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  60. GRB 260402C: NuSTAR detection of prompt emission
  61. EP260324A / AT 2026hir: COLIBRÍ optical observations
  62. GRB 260403A: Fermi GBM Final Real-time Localization
  63. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  64. GRB 260402B: Fermi GBM Final Real-time Localization
  65. GRB260402A: GROWTH-India Telescope optical upper limit
  66. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  67. GRB 260401A: SVOM/GRM observation
  68. GRB 260401A: GECAM-B observation
  69. GRB 260402A: MASTER optical observations
  70. GRB 260402A: SVOM detection of a burst
  71. Fermi GRB 260401A: Global MASTER-Net observations report
  72. GRB 260401A: Fermi GBM Observation
  73. GRB 260401A: NuSTAR detection of prompt emission
  74. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  75. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  76. GRB 260401A: Fermi GBM Final Real-time Localization
  77. EP260321a :Xinglong optical observations
  78. EP260327a: Xinglong optical upper limit
  79. EP260329b: GOTO detection of optical counterpart
  80. GRB 260330B: SVOM/VT optical upper limits
  81. Konus-Wind detection of GRB 260320A
  82. Konus-Wind detection of GRB 260316B
  83. GRB 260321A: SVOM/ECLAIRs refined analysis
  84. Fermi GBM Sub-Threshold Detection of GRB 260330B
  85. GRB 260330B: LCO optical upper limits
  86. GRB 260330B: SVOM detection of a burst
  87. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  88. EP260329a: EP-FXT follow up observation
  89. EP260329a: NOT optical counterpart candidate
  90. GRB 260330A: Fermi GBM Final Real-time Localization
  91. EP260329b: Global MASTER-Net observations report
  92. Fermi trigger No 796485221: Global MASTER-Net observations report
  93. EP260329a: Optical upper limit with Kinder observations
  94. EP-WXT trigger 01709259209: TRT optical counterpart detection
  95. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  96. EP260327a: SVOM/VT optical upper limits
  97. GRB 260307B: ATCA Radio Upper Limits
  98. EP260327a: WINTER J-band upper limit
  99. EP260327a: Gemini-North optical upper limits
  100. EP260324a: GROWTH-India Telescope optical observation

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