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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"

18334 results found.

  1. GRB 260407A: Insight-HXMT/HE detection
  2. EP260409a: COLIBRÍ optical upper limits
  3. EP260409a: Einstein Probe detection of an X-ray transient
  4. EP260321a: VLA radio detection
  5. GRB 260402A: SVOM/ECLAIRs refined analysis
  6. GRB 260310A / AT2026fgk: X-ray rebrightening
  7. EP260402a / GRB 260402A: Mephisto optical upper limits
  8. EP-WXT01709259586: Xinglong optical upper limit
  9. EP260403a: Mephisto optical upper limits
  10. EP260402a/GRB 260402A: Xinglong optical upper limit
  11. EP260405a: GMOS-N optical upper limits
  12. EP260405a: Einstein Probe detection of a fast X-ray transient
  13. The EP-WXT trigger 01709259621 is likely a flaring star
  14. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  15. The EP-WXT trigger 01709259615 is likely a flaring star
  16. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  17. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  18. The EP-WXT trigger 01709259586 is likely a flaring star
  19. GRB 260330B: SVOM/VT further optical observation
  20. EP260403a: LCO optical observations of the counterpart
  21. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  22. EP260403a: LCO optical counterpart detection
  23. EP260403a: COLIBRÍ optical counterpart candidate
  24. GRB 260330B: SVOM/VT optical candidate
  25. EP260403a: Einstein Probe detection of an X-ray transient
  26. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  27. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  28. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  29. EP260324A / AT 2026hir: COLIBRÍ optical observations
  30. GRB 260402A: WINTER J-band upper limit
  31. GRB260402A: GROWTH-India Telescope optical upper limit
  32. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  33. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  34. GRB 260401A: SVOM/GRM observation
  35. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  36. GRB 260402A: Kilonova-Catcher optical upper limit
  37. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  38. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  39. GRB 260402A: SVOM detection of a burst
  40. EP260329b: Mondy and Assy-Turgen optical upper limits
  41. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  42. EP260321a :Xinglong optical observations
  43. EP260327a: Xinglong optical upper limit
  44. GRB 260330B: SVOM/VT optical upper limits
  45. GRB 260321A: SVOM/ECLAIRs refined analysis
  46. EP260329b: J-band upper limits with WINTER
  47. EP260329a: J-band upper limit with WINTER
  48. GRB 260330B: LCO optical upper limits
  49. GRB 260330B: SVOM detection of a burst
  50. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  51. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  52. EP260329a: COLIBRÍ optical upper limit
  53. EP260329a: EP-FXT follow up observation
  54. EP260329a: NOT optical counterpart candidate
  55. EP260329b: Optical follow-up with Kinder observations
  56. EP 260329b: COLIBRÍ optical observations
  57. EP260329a: Optical upper limit with Kinder observations
  58. EP260329b: LCO optical observations of the counterpart
  59. EP260329b: Einstein Probe detection of an X-ray transient
  60. EP260329a: Einstein Probe detection of an X-ray transient
  61. EP-WXT trigger 01709259209: TRT optical counterpart detection
  62. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  63. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  64. EP260327a: SVOM/VT optical upper limits
  65. EP260327a: WINTER J-band upper limit
  66. EP260327a: COLIBRÍ optical upper limits
  67. EP260327a: Gemini-North optical upper limits
  68. EP260324a: GROWTH-India Telescope optical observation
  69. EP260327a: Einstein Probe detection of an X-ray transient
  70. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  71. The EP-WXT trigger 01709259173 is likely a flaring star
  72. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  73. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  74. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  75. EP260321a: JinShan near-infrared observations
  76. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  77. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  78. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  79. The EP-WXT trigger 01709259112 is likely a flaring star
  80. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  81. EP260321a: COLIBRÍ further optical observations and brightening
  82. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  83. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  84. GRB 260321A: EP-FXT follow-up observation
  85. The EP-WXT trigger 01709259045 is likely a flaring star
  86. EP260321a: GOTO detection of blue variable source
  87. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  88. EP260321a: further Kinder optical observations
  89. GRB 260321A: SVOM/VT optical upper limits
  90. EP260321a: Las Cumbres upper limit
  91. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  92. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  93. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  94. EP260321a: SVOM/VT optical upper limit
  95. GRB 260310A: continued optical observation at Mondy
  96. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  97. EP260321a: Einstein Probe detection of an X-ray transient
  98. GRB 260310A / AT 2026fgk: KAIT optical observations
  99. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  100. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening

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