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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"

3296 results found.

  1. EP260417b: GROWTH-India Telescope optical upper limit
  2. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  3. EP260417a: Global MASTER-Net observations report
  4. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  5. Konus-Wind detection of GRB 260411B
  6. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  7. EP260417a: TRT optical counterpart detection
  8. EP260417a: Einstein Probe detection of an X-ray transient
  9. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  10. EP260417b: Einstein Probe detection of a fast X-ray transient
  11. EP-WXT trigger 01709259586: KAIT optical observations
  12. EP260416a: COLIBRÍ optical counterpart candidate
  13. EP260416a: Global MASTER-Net observations report
  14. EP260416a: Einstein Probe detection of an X-ray transient
  15. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  16. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  17. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  18. The EP-WXT trigger 01709260122 is likely a flaring star
  19. Konus-Wind detection of GRB 260410A (short/hard)
  20. The EP-WXT trigger 01709260010 is likely a flaring star
  21. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  22. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  23. EP-WXT01709259790: Optical Upper limits with kinder observations
  24. The EP-WXT trigger 01709259790 is likely a flaring star
  25. EP-WXT01709259790: Xinglong optical upper limit
  26. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  27. EP260321a: Chandra X-ray Non-detection
  28. The EP-WXT trigger 01709259773 is likely a flaring star
  29. EP260409a: SVOM/VT optical upper limits
  30. EP260409a: COLIBRÍ optical upper limits
  31. EP260409a: Global MASTER-Net observations report
  32. EP260409a: Einstein Probe detection of an X-ray transient
  33. GRB 260402A: SVOM/ECLAIRs refined analysis
  34. GRB 260310A / AT2026fgk: X-ray rebrightening
  35. EP260402a / GRB 260402A: Mephisto optical upper limits
  36. EP-WXT01709259586: Xinglong optical upper limit
  37. EP260402a/GRB 260402A: Xinglong optical upper limit
  38. EP260321a: uGMRT observations
  39. EP260405a: GMOS-N optical upper limits
  40. EP260405a: SVOM/VT optical upper limits
  41. EP260405a: Global MASTER-Net observations report
  42. EP260405a: Einstein Probe detection of a fast X-ray transient
  43. The EP-WXT trigger 01709259621 is likely a flaring star
  44. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  45. The EP-WXT trigger 01709259615 is likely a flaring star
  46. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  47. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  48. The EP-WXT trigger 01709259586 is likely a flaring star
  49. EP260403a: LCO optical observations of the counterpart
  50. EP260403a: LCO optical counterpart detection
  51. EP260403a: COLIBRÍ optical counterpart candidate
  52. GRB 260330B: SVOM/VT optical candidate
  53. EP260403a: Einstein Probe detection of an X-ray transient
  54. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  55. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  56. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  57. EP260324A / AT 2026hir: COLIBRÍ optical observations
  58. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  59. GRB 260402A: WINTER J-band upper limit
  60. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  61. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  62. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  63. EP260329b: Mondy and Assy-Turgen optical upper limits
  64. EP260321a :Xinglong optical observations
  65. EP260327a: Xinglong optical upper limit
  66. EP260329b: GOTO detection of optical counterpart
  67. Konus-Wind detection of GRB 260320A
  68. Konus-Wind detection of GRB 260316B
  69. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  70. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  71. EP260329a: COLIBRÍ optical upper limit
  72. EP260329a: EP-FXT follow up observation
  73. EP260329a: NOT optical counterpart candidate
  74. EP260329b: Global MASTER-Net observations report
  75. EP260329b: Optical follow-up with Kinder observations
  76. EP 260329b: COLIBRÍ optical observations
  77. EP260329a: Optical upper limit with Kinder observations
  78. EP260329b: Einstein Probe detection of an X-ray transient
  79. EP260329a: Einstein Probe detection of an X-ray transient
  80. EP-WXT trigger 01709259209: TRT optical counterpart detection
  81. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  82. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  83. EP260327a: SVOM/VT optical upper limits
  84. EP260327a: WINTER J-band upper limit
  85. EP260327a: COLIBRÍ optical upper limits
  86. EP260327a: Gemini-North optical upper limits
  87. EP260327a: Global MASTER-Net observations report
  88. EP260327a: Einstein Probe detection of an X-ray transient
  89. The EP-WXT trigger 01709259173 is likely a flaring star
  90. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  91. EP260321a: Gemini-South confirmation of a supernova
  92. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  93. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  94. The EP-WXT trigger 01709259112 is likely a flaring star
  95. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  96. EP260321a: COLIBRÍ further optical observations and brightening
  97. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  98. EP260214b: ATCA 6 GHz detection
  99. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  100. GRB 260321A: EP-FXT follow-up observation

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