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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"

45742 results found.

  1. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  2. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  3. GRB 260411B: Fermi GBM Final Real-time Localization
  4. GRB 260411A: Fermi GBM Final Real-time Localization
  5. GRB 260410A: COLIBRÍ optical upper limit
  6. EP-WXT01709259790: Optical Upper limits with kinder observations
  7. GRB 260410A: Fermi GBM Observation
  8. GRB 260410B: SVOM/GRM detection of a short faint burst
  9. The EP-WXT trigger 01709259790 is likely a flaring star
  10. GRB 260410B: Fermi GBM Final Real-time Localization
  11. EP-WXT01709259790: Xinglong optical upper limit
  12. GRB 260410A: Fermi-LAT detection
  13. GRB 260410A: Fermi GBM Final Real-time Localization
  14. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  15. EP260321a: Chandra X-ray Non-detection
  16. GRB 260409A: Fermi GBM Final Real-time Localization
  17. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  18. The EP-WXT trigger 01709259773 is likely a flaring star
  19. GRB 260407A: GECAM-A detection
  20. GRB 260407A: Insight-HXMT/HE detection
  21. EP260409a: SVOM/VT optical upper limits
  22. EP260409a: COLIBRÍ optical upper limits
  23. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  24. EP260409a: Global MASTER-Net observations report
  25. EP260409a: Einstein Probe detection of an X-ray transient
  26. EP260321a: VLA radio detection
  27. GRB 260404A: Fermi GBM Final Localization
  28. GRB 260407A: Glowbug gamma-ray detection
  29. GRB 260402A: SVOM/ECLAIRs refined analysis
  30. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  31. GRB 260310A / AT2026fgk: X-ray rebrightening
  32. EP260402a / GRB 260402A: Mephisto optical upper limits
  33. EP-WXT01709259586: Xinglong optical upper limit
  34. EP260403a: Mephisto optical upper limits
  35. EP260402a/GRB 260402A: Xinglong optical upper limit
  36. EP260321a: Upper limits from VLA radio observations
  37. GRID detection of GRB 260401A
  38. EP260321a: uGMRT observations
  39. GRB 260407A: Fermi GBM Final Real-time Localization
  40. EP260405a: GMOS-N optical upper limits
  41. EP260405a: SVOM/VT optical upper limits
  42. EP260405a: Global MASTER-Net observations report
  43. EP260405a: Einstein Probe detection of a fast X-ray transient
  44. The EP-WXT trigger 01709259621 is likely a flaring star
  45. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  46. The EP-WXT trigger 01709259615 is likely a flaring star
  47. Fermi trigger No 797039833: Global MASTER-Net observations report
  48. GRB 260403A: GECAM-B observation of a long burst
  49. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  50. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  51. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  52. The EP-WXT trigger 01709259586 is likely a flaring star
  53. GRB 260330B: SVOM/VT further optical observation
  54. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  55. GRB 260330B: SVOM/ECLAIRs refined analysis
  56. EP260403a: LCO optical observations of the counterpart
  57. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  58. EP260403a: LCO optical counterpart detection
  59. EP260403a: COLIBRÍ optical counterpart candidate
  60. GRB 260330B: SVOM/VT optical candidate
  61. EP260403a: Einstein Probe detection of an X-ray transient
  62. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  63. GRB 260403A: AstroSat CZTI detection
  64. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  65. GRB 260402B: GECAM-B observation
  66. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  67. GRB 260402C: NuSTAR detection of prompt emission
  68. GRB 260402C: AstroSat CZTI detection of a long burst
  69. EP260324A / AT 2026hir: COLIBRÍ optical observations
  70. GRB 260403A: Fermi GBM Final Real-time Localization
  71. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  72. GRB 260402B: Fermi GBM Final Real-time Localization
  73. GRB 260402A: WINTER J-band upper limit
  74. GRB260402A: GROWTH-India Telescope optical upper limit
  75. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  76. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  77. GRB 260401A: SVOM/GRM observation
  78. GRB 260401A: GECAM-B observation
  79. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  80. GRB 260402A: Kilonova-Catcher optical upper limit
  81. GRB 260402A: MASTER optical observations
  82. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  83. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  84. GRB 260402A: SVOM detection of a burst
  85. Fermi GRB 260401A: Global MASTER-Net observations report
  86. GRB 260401A: Fermi GBM Observation
  87. GRB 260401A: NuSTAR detection of prompt emission
  88. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  89. GRB 260401A: MAXI/GSC detection
  90. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  91. GRB 260401A: Fermi GBM Final Real-time Localization
  92. EP260329b: Mondy and Assy-Turgen optical upper limits
  93. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  94. EP260321a :Xinglong optical observations
  95. EP260327a: Xinglong optical upper limit
  96. EP260329b: GOTO detection of optical counterpart
  97. GRB 260330B: SVOM/VT optical upper limits
  98. Konus-Wind detection of GRB 260320A
  99. Konus-Wind detection of GRB 260316B (duplicate submission)
  100. Konus-Wind detection of GRB 260316B

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