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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"

17638 results found.

  1. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  2. GRB 260409A: Fermi GBM Final Real-time Localization
  3. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  4. The EP-WXT trigger 01709259773 is likely a flaring star
  5. GRB 260407A: Insight-HXMT/HE detection
  6. EP260409a: COLIBRÍ optical upper limits
  7. EP260409a: Einstein Probe detection of an X-ray transient
  8. EP260321a: VLA radio detection
  9. GRB 260402A: SVOM/ECLAIRs refined analysis
  10. GRB 260310A / AT2026fgk: X-ray rebrightening
  11. EP260402a / GRB 260402A: Mephisto optical upper limits
  12. EP-WXT01709259586: Xinglong optical upper limit
  13. EP260403a: Mephisto optical upper limits
  14. EP260402a/GRB 260402A: Xinglong optical upper limit
  15. EP260405a: GMOS-N optical upper limits
  16. EP260405a: Einstein Probe detection of a fast X-ray transient
  17. The EP-WXT trigger 01709259621 is likely a flaring star
  18. EP260405.149 / EP-WXT 11900672904: COLIBRÍ optical upper limits
  19. The EP-WXT trigger 01709259615 is likely a flaring star
  20. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  21. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  22. The EP-WXT trigger 01709259586 is likely a flaring star
  23. GRB 260330B: SVOM/VT further optical observation
  24. EP260403a: LCO optical observations of the counterpart
  25. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  26. EP260403a: LCO optical counterpart detection
  27. EP260403a: COLIBRÍ optical counterpart candidate
  28. GRB 260330B: SVOM/VT optical candidate
  29. EP260403a: Einstein Probe detection of an X-ray transient
  30. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  31. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  32. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  33. EP260324A / AT 2026hir: COLIBRÍ optical observations
  34. GRB 260402A: WINTER J-band upper limit
  35. GRB260402A: GROWTH-India Telescope optical upper limit
  36. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  37. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  38. GRB 260401A: SVOM/GRM observation
  39. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  40. GRB 260402A: Kilonova-Catcher optical upper limit
  41. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  42. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  43. GRB 260402A: SVOM detection of a burst
  44. EP260329b: Mondy and Assy-Turgen optical upper limits
  45. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  46. EP260321a :Xinglong optical observations
  47. EP260327a: Xinglong optical upper limit
  48. GRB 260330B: SVOM/VT optical upper limits
  49. GRB 260321A: SVOM/ECLAIRs refined analysis
  50. EP260329b: J-band upper limits with WINTER
  51. EP260329a: J-band upper limit with WINTER
  52. GRB 260330B: LCO optical upper limits
  53. GRB 260330B: SVOM detection of a burst
  54. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  55. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  56. EP260329a: COLIBRÍ optical upper limit
  57. EP260329a: EP-FXT follow up observation
  58. EP260329a: NOT optical counterpart candidate
  59. EP260329b: Optical follow-up with Kinder observations
  60. EP 260329b: COLIBRÍ optical observations
  61. EP260329a: Optical upper limit with Kinder observations
  62. EP260329b: LCO optical observations of the counterpart
  63. EP260329b: Einstein Probe detection of an X-ray transient
  64. EP260329a: Einstein Probe detection of an X-ray transient
  65. EP-WXT trigger 01709259209: TRT optical counterpart detection
  66. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  67. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  68. EP260327a: SVOM/VT optical upper limits
  69. EP260327a: WINTER J-band upper limit
  70. EP260327a: COLIBRÍ optical upper limits
  71. EP260327a: Gemini-North optical upper limits
  72. EP260324a: GROWTH-India Telescope optical observation
  73. EP260327a: Einstein Probe detection of an X-ray transient
  74. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  75. The EP-WXT trigger 01709259173 is likely a flaring star
  76. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  77. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  78. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  79. EP260321a: JinShan near-infrared observations
  80. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  81. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  82. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  83. The EP-WXT trigger 01709259112 is likely a flaring star
  84. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  85. EP260321a: COLIBRÍ further optical observations and brightening
  86. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  87. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  88. GRB 260321A: EP-FXT follow-up observation
  89. The EP-WXT trigger 01709259045 is likely a flaring star
  90. EP260321a: GOTO detection of blue variable source
  91. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  92. EP260321a: further Kinder optical observations
  93. GRB 260321A: SVOM/VT optical upper limits
  94. EP260321a: Las Cumbres upper limit
  95. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  96. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  97. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  98. EP260321a: SVOM/VT optical upper limit
  99. GRB 260310A: continued optical observation at Mondy
  100. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle

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