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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

42854 results found.

  1. GRB 260412A: Insight-HXMT/HE detection
  2. GRB 260414A: Fermi GBM Final Real-time Localization
  3. The EP-WXT trigger 01709260122 is likely a flaring star
  4. Fermi GRB 260413A: Global MASTER-Net observations report
  5. GRB 260410A: Glowbug gamma-ray detection of a short burst
  6. GRB 260413A: Fermi GBM Final Real-time Localization
  7. GRB 260410B: Insight-HXMT/HE detection
  8. GRB 260410A: Insight-HXMT/HE detection
  9. Konus-Wind detection of GRB 260410A (short/hard)
  10. GRB 260411B: GECAM-B observation of a long burst
  11. EP260321a: SVOM/VT optical observations and color changes around peak
  12. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  13. The EP-WXT trigger 01709260010 is likely a flaring star
  14. GRB 260412A: GECAM-B observation of a long burst
  15. Fermi GRB 260412A: Global MASTER-Net observations report
  16. GRB 260412A: Fermi GBM Observation
  17. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  18. GRB 260411B: Fermi-LAT detection
  19. GRB 260412A: SVOM detection of a long burst
  20. GRB 260412A: Fermi GBM Final Real-time Localization
  21. GRB 260411B: COLIBRÍ optical observations
  22. GRB 260410B: Fermi GBM Observation
  23. GRB 260411B: Ondrejov D50 optical afterglow detection
  24. GRB 260411A: SVOM/GRM observation
  25. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  26. GRB 260411B: SVOM/GRM observation of a long burst
  27. GRB 260409A: Insight-HXMT/HE detection
  28. GRB 260411B: Fermi GBM Detection
  29. GRB 260411B: GOTO optical counterpart candidate
  30. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  31. GRB 260411B: Fermi GBM Final Real-time Localization
  32. GRB 260411A: Fermi GBM Final Real-time Localization
  33. GRB 260410A: COLIBRÍ optical upper limit
  34. EP-WXT01709259790: Optical Upper limits with kinder observations
  35. GRB 260410A: Fermi GBM Observation
  36. GRB 260410B: SVOM/GRM detection of a short faint burst
  37. The EP-WXT trigger 01709259790 is likely a flaring star
  38. GRB 260410B: Fermi GBM Final Real-time Localization
  39. EP-WXT01709259790: Xinglong optical upper limit
  40. GRB 260410A: Fermi-LAT detection
  41. GRB 260410A: Fermi GBM Final Real-time Localization
  42. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  43. EP260321a: Chandra X-ray Non-detection
  44. GRB 260409A: Fermi GBM Final Real-time Localization
  45. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  46. The EP-WXT trigger 01709259773 is likely a flaring star
  47. GRB 260407A: GECAM-A detection
  48. GRB 260407A: Insight-HXMT/HE detection
  49. EP260409a: SVOM/VT optical upper limits
  50. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  51. EP260409a: Global MASTER-Net observations report
  52. EP260409a: Einstein Probe detection of an X-ray transient
  53. EP260321a: VLA radio detection
  54. GRB 260404A: Fermi GBM Final Localization
  55. GRB 260407A: Glowbug gamma-ray detection
  56. GRB 260402A: SVOM/ECLAIRs refined analysis
  57. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  58. GRB 260310A / AT2026fgk: X-ray rebrightening
  59. EP260402a / GRB 260402A: Mephisto optical upper limits
  60. EP-WXT01709259586: Xinglong optical upper limit
  61. EP260403a: Mephisto optical upper limits
  62. EP260402a/GRB 260402A: Xinglong optical upper limit
  63. EP260321a: Upper limits from VLA radio observations
  64. GRID detection of GRB 260401A
  65. EP260321a: uGMRT observations
  66. GRB 260407A: Fermi GBM Final Real-time Localization
  67. EP260405a: GMOS-N optical upper limits
  68. EP260405a: SVOM/VT optical upper limits
  69. EP260405a: Global MASTER-Net observations report
  70. EP260405a: Einstein Probe detection of a fast X-ray transient
  71. The EP-WXT trigger 01709259621 is likely a flaring star
  72. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  73. The EP-WXT trigger 01709259615 is likely a flaring star
  74. Fermi trigger No 797039833: Global MASTER-Net observations report
  75. GRB 260403A: GECAM-B observation of a long burst
  76. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  77. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  78. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  79. The EP-WXT trigger 01709259586 is likely a flaring star
  80. GRB 260330B: SVOM/VT further optical observation
  81. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  82. GRB 260330B: SVOM/ECLAIRs refined analysis
  83. EP260403a: LCO optical observations of the counterpart
  84. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  85. EP260403a: LCO optical counterpart detection
  86. GRB 260330B: SVOM/VT optical candidate
  87. EP260403a: Einstein Probe detection of an X-ray transient
  88. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  89. GRB 260403A: AstroSat CZTI detection
  90. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  91. GRB 260402B: GECAM-B observation
  92. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  93. GRB 260402C: NuSTAR detection of prompt emission
  94. GRB 260402C: AstroSat CZTI detection of a long burst
  95. GRB 260403A: Fermi GBM Final Real-time Localization
  96. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  97. GRB 260402B: Fermi GBM Final Real-time Localization
  98. GRB 260402A: WINTER J-band upper limit
  99. GRB260402A: GROWTH-India Telescope optical upper limit
  100. GRB 260402A / EP260402a: SVOM/VT optical upper limits

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