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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"

44404 results found.

  1. EP260409a: SVOM/VT optical upper limits
  2. EP260409a: COLIBRÍ optical upper limits
  3. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  4. EP260409a: Global MASTER-Net observations report
  5. EP260409a: Einstein Probe detection of an X-ray transient
  6. EP260321a: VLA radio detection
  7. GRB 260404A: Fermi GBM Final Localization
  8. GRB 260407A: Glowbug gamma-ray detection
  9. GRB 260402A: SVOM/ECLAIRs refined analysis
  10. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  11. GRB 260310A / AT2026fgk: X-ray rebrightening
  12. EP260402a / GRB 260402A: Mephisto optical upper limits
  13. EP-WXT01709259586: Xinglong optical upper limit
  14. EP260403a: Mephisto optical upper limits
  15. EP260402a/GRB 260402A: Xinglong optical upper limit
  16. EP260321a: Upper limits from VLA radio observations
  17. GRID detection of GRB 260401A
  18. EP260321a: uGMRT observations
  19. GRB 260407A: Fermi GBM Final Real-time Localization
  20. EP260405a: GMOS-N optical upper limits
  21. EP260405a: SVOM/VT optical upper limits
  22. EP260405a: Global MASTER-Net observations report
  23. EP260405a: Einstein Probe detection of a fast X-ray transient
  24. The EP-WXT trigger 01709259621 is likely a flaring star
  25. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  26. The EP-WXT trigger 01709259615 is likely a flaring star
  27. Fermi trigger No 797039833: Global MASTER-Net observations report
  28. GRB 260403A: GECAM-B observation of a long burst
  29. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  30. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  31. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  32. The EP-WXT trigger 01709259586 is likely a flaring star
  33. GRB 260330B: SVOM/VT further optical observation
  34. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  35. GRB 260330B: SVOM/ECLAIRs refined analysis
  36. EP260403a: LCO optical observations of the counterpart
  37. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  38. EP260403a: LCO optical counterpart detection
  39. EP260403a: COLIBRÍ optical counterpart candidate
  40. GRB 260330B: SVOM/VT optical candidate
  41. EP260403a: Einstein Probe detection of an X-ray transient
  42. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  43. GRB 260403A: AstroSat CZTI detection
  44. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  45. GRB 260402B: GECAM-B observation
  46. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  47. GRB 260402C: NuSTAR detection of prompt emission
  48. GRB 260402C: AstroSat CZTI detection of a long burst
  49. EP260324A / AT 2026hir: COLIBRÍ optical observations
  50. GRB 260403A: Fermi GBM Final Real-time Localization
  51. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  52. GRB 260402B: Fermi GBM Final Real-time Localization
  53. GRB 260402A: WINTER J-band upper limit
  54. GRB260402A: GROWTH-India Telescope optical upper limit
  55. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  56. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  57. GRB 260401A: SVOM/GRM observation
  58. GRB 260401A: GECAM-B observation
  59. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  60. GRB 260402A: Kilonova-Catcher optical upper limit
  61. GRB 260402A: MASTER optical observations
  62. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  63. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  64. GRB 260402A: SVOM detection of a burst
  65. Fermi GRB 260401A: Global MASTER-Net observations report
  66. GRB 260401A: Fermi GBM Observation
  67. GRB 260401A: NuSTAR detection of prompt emission
  68. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  69. GRB 260401A: MAXI/GSC detection
  70. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  71. GRB 260401A: Fermi GBM Final Real-time Localization
  72. EP260329b: Mondy and Assy-Turgen optical upper limits
  73. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  74. EP260321a :Xinglong optical observations
  75. EP260327a: Xinglong optical upper limit
  76. EP260329b: GOTO detection of optical counterpart
  77. GRB 260330B: SVOM/VT optical upper limits
  78. Konus-Wind detection of GRB 260320A
  79. Konus-Wind detection of GRB 260316B (duplicate submission)
  80. Konus-Wind detection of GRB 260316B
  81. GRB 260321A: SVOM/ECLAIRs refined analysis
  82. EP260329b: J-band upper limits with WINTER
  83. EP260329a: J-band upper limit with WINTER
  84. GRB 260330A: Glowbug gamma-ray detection
  85. GRB 260310A: VLA Multi-frequency Radio Observations
  86. Fermi GBM Sub-Threshold Detection of GRB 260330B
  87. GRB 260330B: LCO optical upper limits
  88. GRB 260330B: SVOM detection of a burst
  89. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  90. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  91. EP260329a: COLIBRÍ optical upper limit
  92. EP260329a: EP-FXT follow up observation
  93. EP260329a: NOT optical counterpart candidate
  94. GRB 260330A: Fermi GBM Final Real-time Localization
  95. EP260329b: Global MASTER-Net observations report
  96. Fermi trigger No 796485221: Global MASTER-Net observations report
  97. GRB 260327A: Insight-HXMT/HE detection
  98. EP260329b: Optical follow-up with Kinder observations
  99. EP 260329b: COLIBRÍ optical observations
  100. EP260329a: Optical upper limit with Kinder observations

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