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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"

26764 results found.

  1. GRB 260411B: Ondrejov D50 optical afterglow detection
  2. GRB260411B: 3.6m DOT optical observation
  3. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  4. GRB 260411B: SVOM/GRM observation of a long burst
  5. GRB 260411B: Fermi GBM Detection
  6. GRB 260411B: GOTO optical counterpart candidate
  7. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  8. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  9. GRB 260411B: Fermi GBM Final Real-time Localization
  10. GRB 260411A: Fermi GBM Final Real-time Localization
  11. GRB 260410A: COLIBRÍ optical upper limit
  12. EP-WXT01709259790: Optical Upper limits with kinder observations
  13. GRB 260410A: Fermi GBM Observation
  14. The EP-WXT trigger 01709259790 is likely a flaring star
  15. GRB 260410B: Fermi GBM Final Real-time Localization
  16. EP-WXT01709259790: Xinglong optical upper limit
  17. GRB 260410A: Fermi-LAT detection
  18. GRB 260410A: Fermi GBM Final Real-time Localization
  19. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  20. EP260321a: Chandra X-ray Non-detection
  21. GRB 260409A: Fermi GBM Final Real-time Localization
  22. The EP-WXT trigger 01709259773 is likely a flaring star
  23. EP260409a: SVOM/VT optical upper limits
  24. EP260409a: COLIBRÍ optical upper limits
  25. EP260409a: Global MASTER-Net observations report
  26. EP260321a: VLA radio detection
  27. GRB 260404A: Fermi GBM Final Localization
  28. GRB 260402A: SVOM/ECLAIRs refined analysis
  29. EP260402a / GRB 260402A: Mephisto optical upper limits
  30. EP-WXT01709259586: Xinglong optical upper limit
  31. EP260403a: Mephisto optical upper limits
  32. EP260402a/GRB 260402A: Xinglong optical upper limit
  33. EP260321a: Upper limits from VLA radio observations
  34. EP260321a: uGMRT observations
  35. GRB 260407A: Fermi GBM Final Real-time Localization
  36. EP260405a: GMOS-N optical upper limits
  37. EP260405a: SVOM/VT optical upper limits
  38. EP260405a: Global MASTER-Net observations report
  39. EP260405a: Einstein Probe detection of a fast X-ray transient
  40. The EP-WXT trigger 01709259621 is likely a flaring star
  41. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  42. The EP-WXT trigger 01709259615 is likely a flaring star
  43. Fermi trigger No 797039833: Global MASTER-Net observations report
  44. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  45. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  46. The EP-WXT trigger 01709259586 is likely a flaring star
  47. GRB 260330B: SVOM/VT further optical observation
  48. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  49. GRB 260330B: SVOM/ECLAIRs refined analysis
  50. EP260403a: LCO optical observations of the counterpart
  51. EP260403a: LCO optical counterpart detection
  52. EP260403a: COLIBRÍ optical counterpart candidate
  53. GRB 260330B: SVOM/VT optical candidate
  54. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  55. EP260324A / AT 2026hir: COLIBRÍ optical observations
  56. GRB 260403A: Fermi GBM Final Real-time Localization
  57. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  58. GRB 260402B: Fermi GBM Final Real-time Localization
  59. GRB 260402A: WINTER J-band upper limit
  60. GRB260402A: GROWTH-India Telescope optical upper limit
  61. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  62. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  63. GRB 260401A: SVOM/GRM observation
  64. GRB 260402A: MASTER optical observations
  65. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  66. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  67. GRB 260402A: SVOM detection of a burst
  68. Fermi GRB 260401A: Global MASTER-Net observations report
  69. GRB 260401A: Fermi GBM Observation
  70. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  71. GRB 260401A: Fermi GBM Final Real-time Localization
  72. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  73. EP260321a :Xinglong optical observations
  74. EP260327a: Xinglong optical upper limit
  75. EP260329b: GOTO detection of optical counterpart
  76. GRB 260330B: SVOM/VT optical upper limits
  77. GRB 260321A: SVOM/ECLAIRs refined analysis
  78. EP260329b: J-band upper limits with WINTER
  79. EP260329a: J-band upper limit with WINTER
  80. Fermi GBM Sub-Threshold Detection of GRB 260330B
  81. GRB 260330B: LCO optical upper limits
  82. GRB 260330B: SVOM detection of a burst
  83. EP260329a: COLIBRÍ optical upper limit
  84. EP260329a: EP-FXT follow up observation
  85. EP260329a: NOT optical counterpart candidate
  86. GRB 260330A: Fermi GBM Final Real-time Localization
  87. EP260329b: Global MASTER-Net observations report
  88. Fermi trigger No 796485221: Global MASTER-Net observations report
  89. EP 260329b: COLIBRÍ optical observations
  90. EP260329b: LCO optical observations of the counterpart
  91. EP-WXT trigger 01709259209: TRT optical counterpart detection
  92. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  93. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  94. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  95. EP260327a: SVOM/VT optical upper limits
  96. EP260327a: WINTER J-band upper limit
  97. EP260327a: COLIBRÍ optical upper limits
  98. EP260327a: Gemini-North optical upper limits
  99. EP260324a: GROWTH-India Telescope optical observation
  100. EP260327a: Global MASTER-Net observations report

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