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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"

32549 results found.

  1. EP260321a: Chandra X-ray Non-detection
  2. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  3. GRB 260407A: GECAM-A detection
  4. GRB 260407A: Insight-HXMT/HE detection
  5. EP260409a: SVOM/VT optical upper limits
  6. EP260409a: COLIBRÍ optical upper limits
  7. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  8. EP260409a: Global MASTER-Net observations report
  9. EP260321a: VLA radio detection
  10. GRB 260407A: Glowbug gamma-ray detection
  11. GRB 260402A: SVOM/ECLAIRs refined analysis
  12. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  13. GRB 260310A / AT2026fgk: X-ray rebrightening
  14. EP260402a / GRB 260402A: Mephisto optical upper limits
  15. EP-WXT01709259586: Xinglong optical upper limit
  16. EP260403a: Mephisto optical upper limits
  17. EP260402a/GRB 260402A: Xinglong optical upper limit
  18. EP260321a: Upper limits from VLA radio observations
  19. GRID detection of GRB 260401A
  20. EP260321a: uGMRT observations
  21. EP260405a: GMOS-N optical upper limits
  22. EP260405a: SVOM/VT optical upper limits
  23. EP260405a: Global MASTER-Net observations report
  24. EP260405a: Einstein Probe detection of a fast X-ray transient
  25. GRB 260403A: GECAM-B observation of a long burst
  26. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  27. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  28. GRB 260330B: SVOM/VT further optical observation
  29. GRB 260330B: SVOM/ECLAIRs refined analysis
  30. EP260403a: LCO optical observations of the counterpart
  31. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  32. EP260403a: LCO optical counterpart detection
  33. EP260403a: COLIBRÍ optical counterpart candidate
  34. GRB 260330B: SVOM/VT optical candidate
  35. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  36. GRB 260403A: AstroSat CZTI detection
  37. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  38. GRB 260402B: GECAM-B observation
  39. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  40. GRB 260402C: NuSTAR detection of prompt emission
  41. EP260324A / AT 2026hir: COLIBRÍ optical observations
  42. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  43. GRB 260402A: WINTER J-band upper limit
  44. GRB260402A: GROWTH-India Telescope optical upper limit
  45. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  46. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  47. GRB 260401A: SVOM/GRM observation
  48. GRB 260401A: GECAM-B observation
  49. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  50. GRB 260402A: Kilonova-Catcher optical upper limit
  51. GRB 260402A: MASTER optical observations
  52. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  53. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  54. Fermi GRB 260401A: Global MASTER-Net observations report
  55. GRB 260401A: Fermi GBM Observation
  56. GRB 260401A: NuSTAR detection of prompt emission
  57. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  58. GRB 260401A: MAXI/GSC detection
  59. EP260329b: Mondy and Assy-Turgen optical upper limits
  60. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  61. EP260321a :Xinglong optical observations
  62. EP260327a: Xinglong optical upper limit
  63. EP260329b: GOTO detection of optical counterpart
  64. GRB 260330B: SVOM/VT optical upper limits
  65. Konus-Wind detection of GRB 260320A
  66. Konus-Wind detection of GRB 260316B (duplicate submission)
  67. Konus-Wind detection of GRB 260316B
  68. GRB 260321A: SVOM/ECLAIRs refined analysis
  69. EP260329b: J-band upper limits with WINTER
  70. EP260329a: J-band upper limit with WINTER
  71. GRB 260330A: Glowbug gamma-ray detection
  72. GRB 260310A: VLA Multi-frequency Radio Observations
  73. Fermi GBM Sub-Threshold Detection of GRB 260330B
  74. GRB 260330B: LCO optical upper limits
  75. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  76. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  77. EP260329a: COLIBRÍ optical upper limit
  78. EP260329a: EP-FXT follow up observation
  79. EP260329a: NOT optical counterpart candidate
  80. EP260329b: Global MASTER-Net observations report
  81. GRB 260327A: Insight-HXMT/HE detection
  82. EP260329b: Optical follow-up with Kinder observations
  83. EP 260329b: COLIBRÍ optical observations
  84. EP260329a: Optical upper limit with Kinder observations
  85. EP260329b: LCO optical observations of the counterpart
  86. GRB 260326A: Insight-HXMT/HE detection
  87. EP260329b: Einstein Probe detection of an X-ray transient
  88. EP-WXT trigger 01709259209: TRT optical counterpart detection
  89. GRID detection of GRB 260326A
  90. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  91. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  92. EP260327a: SVOM/VT optical upper limits
  93. SMA Detection of GRB 260310A / AT 2026fgk
  94. GRB 260307B: ATCA Radio Upper Limits
  95. EP260327a: WINTER J-band upper limit
  96. EP260327a: COLIBRÍ optical upper limits
  97. EP260327a: Gemini-North optical upper limits
  98. EP260324a: GROWTH-India Telescope optical observation
  99. EP260327a: Global MASTER-Net observations report
  100. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova

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