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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"

17640 results found.

  1. The EP-WXT trigger 01709259790 is likely a flaring star
  2. EP-WXT01709259790: Xinglong optical upper limit
  3. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  4. GRB 260409A: Fermi GBM Final Real-time Localization
  5. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  6. The EP-WXT trigger 01709259773 is likely a flaring star
  7. GRB 260407A: Insight-HXMT/HE detection
  8. EP260409a: COLIBRÍ optical upper limits
  9. EP260409a: Einstein Probe detection of an X-ray transient
  10. EP260321a: VLA radio detection
  11. GRB 260402A: SVOM/ECLAIRs refined analysis
  12. GRB 260310A / AT2026fgk: X-ray rebrightening
  13. EP260402a / GRB 260402A: Mephisto optical upper limits
  14. EP-WXT01709259586: Xinglong optical upper limit
  15. EP260403a: Mephisto optical upper limits
  16. EP260402a/GRB 260402A: Xinglong optical upper limit
  17. EP260405a: GMOS-N optical upper limits
  18. EP260405a: Einstein Probe detection of a fast X-ray transient
  19. The EP-WXT trigger 01709259621 is likely a flaring star
  20. EP260405.149 / EP-WXT 11900672904: COLIBRÍ optical upper limits
  21. The EP-WXT trigger 01709259615 is likely a flaring star
  22. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  23. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  24. The EP-WXT trigger 01709259586 is likely a flaring star
  25. GRB 260330B: SVOM/VT further optical observation
  26. EP260403a: LCO optical observations of the counterpart
  27. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  28. EP260403a: LCO optical counterpart detection
  29. EP260403a: COLIBRÍ optical counterpart candidate
  30. GRB 260330B: SVOM/VT optical candidate
  31. EP260403a: Einstein Probe detection of an X-ray transient
  32. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  33. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  34. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  35. EP260324A / AT 2026hir: COLIBRÍ optical observations
  36. GRB 260402A: WINTER J-band upper limit
  37. GRB260402A: GROWTH-India Telescope optical upper limit
  38. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  39. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  40. GRB 260401A: SVOM/GRM observation
  41. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  42. GRB 260402A: Kilonova-Catcher optical upper limit
  43. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  44. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  45. GRB 260402A: SVOM detection of a burst
  46. EP260329b: Mondy and Assy-Turgen optical upper limits
  47. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  48. EP260321a :Xinglong optical observations
  49. EP260327a: Xinglong optical upper limit
  50. GRB 260330B: SVOM/VT optical upper limits
  51. GRB 260321A: SVOM/ECLAIRs refined analysis
  52. EP260329b: J-band upper limits with WINTER
  53. EP260329a: J-band upper limit with WINTER
  54. GRB 260330B: LCO optical upper limits
  55. GRB 260330B: SVOM detection of a burst
  56. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  57. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  58. EP260329a: COLIBRÍ optical upper limit
  59. EP260329a: EP-FXT follow up observation
  60. EP260329a: NOT optical counterpart candidate
  61. EP260329b: Optical follow-up with Kinder observations
  62. EP 260329b: COLIBRÍ optical observations
  63. EP260329a: Optical upper limit with Kinder observations
  64. EP260329b: LCO optical observations of the counterpart
  65. EP260329b: Einstein Probe detection of an X-ray transient
  66. EP260329a: Einstein Probe detection of an X-ray transient
  67. EP-WXT trigger 01709259209: TRT optical counterpart detection
  68. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  69. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  70. EP260327a: SVOM/VT optical upper limits
  71. EP260327a: WINTER J-band upper limit
  72. EP260327a: COLIBRÍ optical upper limits
  73. EP260327a: Gemini-North optical upper limits
  74. EP260324a: GROWTH-India Telescope optical observation
  75. EP260327a: Einstein Probe detection of an X-ray transient
  76. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  77. The EP-WXT trigger 01709259173 is likely a flaring star
  78. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  79. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  80. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  81. EP260321a: JinShan near-infrared observations
  82. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  83. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  84. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  85. The EP-WXT trigger 01709259112 is likely a flaring star
  86. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  87. EP260321a: COLIBRÍ further optical observations and brightening
  88. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  89. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  90. GRB 260321A: EP-FXT follow-up observation
  91. The EP-WXT trigger 01709259045 is likely a flaring star
  92. EP260321a: GOTO detection of blue variable source
  93. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  94. EP260321a: further Kinder optical observations
  95. GRB 260321A: SVOM/VT optical upper limits
  96. EP260321a: Las Cumbres upper limit
  97. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  98. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  99. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  100. EP260321a: SVOM/VT optical upper limit

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