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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"

27594 results found.

  1. EP260416a: LCO observations confirm end of flaring phase
  2. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  3. EP260417a: TRT optical counterpart detection
  4. EP-WXT trigger 01709259586: KAIT optical observations
  5. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  6. EP260416a: WFST optical observations and rebrightening
  7. GRB 260417A: Fermi GBM Final Real-time Localization
  8. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  9. GRB 260415B: Glowbug gamma-ray detection
  10. EP260416a: COLIBRÍ optical counterpart candidate
  11. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  12. EP260416a: Global MASTER-Net observations report
  13. GRB 260415B: NuSTAR detection of long prompt emission
  14. GRB 260415B: Fermi GBM Final Localization
  15. GRB 260415A: Fermi GBM Final Real-time Localization
  16. Fermi trigger No 797912738: Global MASTER-Net observations report
  17. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  18. GRB 260414A: Fermi GBM Final Real-time Localization
  19. The EP-WXT trigger 01709260122 is likely a flaring star
  20. Fermi GRB 260413A: Global MASTER-Net observations report
  21. GRB 260413A: Fermi GBM Final Real-time Localization
  22. EP260321a: SVOM/VT optical observations and color changes around peak
  23. The EP-WXT trigger 01709260010 is likely a flaring star
  24. Fermi GRB 260412A: Global MASTER-Net observations report
  25. GRB 260412A: Fermi GBM Observation
  26. GRB 260411B: Fermi-LAT detection
  27. GRB 260412A: SVOM detection of a long burst
  28. GRB 260412A: Fermi GBM Final Real-time Localization
  29. GRB 260411B: COLIBRÍ optical observations
  30. GRB 260410B: Fermi GBM Observation
  31. GRB 260411B: Ondrejov D50 optical afterglow detection
  32. GRB260411B: 3.6m DOT optical observation
  33. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  34. GRB 260411B: SVOM/GRM observation of a long burst
  35. GRB 260411B: Fermi GBM Detection
  36. GRB 260411B: GOTO optical counterpart candidate
  37. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  38. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  39. GRB 260411B: Fermi GBM Final Real-time Localization
  40. GRB 260411A: Fermi GBM Final Real-time Localization
  41. GRB 260410A: COLIBRÍ optical upper limit
  42. EP-WXT01709259790: Optical Upper limits with kinder observations
  43. GRB 260410A: Fermi GBM Observation
  44. The EP-WXT trigger 01709259790 is likely a flaring star
  45. GRB 260410B: Fermi GBM Final Real-time Localization
  46. EP-WXT01709259790: Xinglong optical upper limit
  47. GRB 260410A: Fermi-LAT detection
  48. GRB 260410A: Fermi GBM Final Real-time Localization
  49. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  50. EP260321a: Chandra X-ray Non-detection
  51. GRB 260409A: Fermi GBM Final Real-time Localization
  52. The EP-WXT trigger 01709259773 is likely a flaring star
  53. EP260409a: SVOM/VT optical upper limits
  54. EP260409a: COLIBRÍ optical upper limits
  55. EP260409a: Global MASTER-Net observations report
  56. EP260321a: VLA radio detection
  57. GRB 260404A: Fermi GBM Final Localization
  58. GRB 260402A: SVOM/ECLAIRs refined analysis
  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. EP260321a: uGMRT observations
  65. GRB 260407A: Fermi GBM Final Real-time Localization
  66. EP260405a: GMOS-N optical upper limits
  67. EP260405a: SVOM/VT optical upper limits
  68. EP260405a: Global MASTER-Net observations report
  69. EP260405a: Einstein Probe detection of a fast X-ray transient
  70. The EP-WXT trigger 01709259621 is likely a flaring star
  71. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  72. The EP-WXT trigger 01709259615 is likely a flaring star
  73. Fermi trigger No 797039833: Global MASTER-Net observations report
  74. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  75. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  76. The EP-WXT trigger 01709259586 is likely a flaring star
  77. GRB 260330B: SVOM/VT further optical observation
  78. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  79. GRB 260330B: SVOM/ECLAIRs refined analysis
  80. EP260403a: LCO optical observations of the counterpart
  81. EP260403a: LCO optical counterpart detection
  82. EP260403a: COLIBRÍ optical counterpart candidate
  83. GRB 260330B: SVOM/VT optical candidate
  84. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  85. EP260324A / AT 2026hir: COLIBRÍ optical observations
  86. GRB 260403A: Fermi GBM Final Real-time Localization
  87. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  88. GRB 260402B: Fermi GBM Final Real-time Localization
  89. GRB 260402A: WINTER J-band upper limit
  90. GRB260402A: GROWTH-India Telescope optical upper limit
  91. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  92. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  93. GRB 260401A: SVOM/GRM observation
  94. GRB 260402A: MASTER optical observations
  95. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  96. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  97. GRB 260402A: SVOM detection of a burst
  98. Fermi GRB 260401A: Global MASTER-Net observations report
  99. GRB 260401A: Fermi GBM Observation
  100. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)

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