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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"

17850 results found.

  1. The EP-WXT trigger 01709260122 is likely a flaring star
  2. The EP-WXT trigger 01709260010 is likely a flaring star
  3. GRB 260411B: Fermi-LAT detection
  4. GRB 260411B: COLIBRÍ optical observations
  5. GRB260411B: 3.6m DOT optical observation
  6. GRB 260411A: SVOM/GRM observation
  7. GRB 260411B: SVOM/GRM observation of a long burst
  8. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  9. GRB 260410A: COLIBRÍ optical upper limit
  10. EP-WXT01709259790: Optical Upper limits with kinder observations
  11. The EP-WXT trigger 01709259790 is likely a flaring star
  12. EP-WXT01709259790: Xinglong optical upper limit
  13. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  14. GRB 260409A: Fermi GBM Final Real-time Localization
  15. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  16. The EP-WXT trigger 01709259773 is likely a flaring star
  17. GRB 260407A: Insight-HXMT/HE detection
  18. EP260409a: COLIBRÍ optical upper limits
  19. EP260409a: Einstein Probe detection of an X-ray transient
  20. EP260321a: VLA radio detection
  21. GRB 260402A: SVOM/ECLAIRs refined analysis
  22. GRB 260310A / AT2026fgk: X-ray rebrightening
  23. EP260402a / GRB 260402A: Mephisto optical upper limits
  24. EP-WXT01709259586: Xinglong optical upper limit
  25. EP260403a: Mephisto optical upper limits
  26. EP260402a/GRB 260402A: Xinglong optical upper limit
  27. EP260405a: GMOS-N optical upper limits
  28. EP260405a: Einstein Probe detection of a fast X-ray transient
  29. The EP-WXT trigger 01709259621 is likely a flaring star
  30. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  31. The EP-WXT trigger 01709259615 is likely a flaring star
  32. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  33. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  34. The EP-WXT trigger 01709259586 is likely a flaring star
  35. GRB 260330B: SVOM/VT further optical observation
  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. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  44. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  45. EP260324A / AT 2026hir: COLIBRÍ optical observations
  46. GRB 260402A: WINTER J-band upper limit
  47. GRB260402A: GROWTH-India Telescope optical upper limit
  48. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  49. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  50. GRB 260401A: SVOM/GRM observation
  51. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  52. GRB 260402A: Kilonova-Catcher optical upper limit
  53. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  54. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  55. GRB 260402A: SVOM detection of a burst
  56. EP260329b: Mondy and Assy-Turgen optical upper limits
  57. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  58. EP260321a :Xinglong optical observations
  59. EP260327a: Xinglong optical upper limit
  60. GRB 260330B: SVOM/VT optical upper limits
  61. GRB 260321A: SVOM/ECLAIRs refined analysis
  62. EP260329b: J-band upper limits with WINTER
  63. EP260329a: J-band upper limit with WINTER
  64. GRB 260330B: LCO optical upper limits
  65. GRB 260330B: SVOM detection of a burst
  66. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  67. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  68. EP260329a: COLIBRÍ optical upper limit
  69. EP260329a: EP-FXT follow up observation
  70. EP260329a: NOT optical counterpart candidate
  71. EP260329b: Optical follow-up with Kinder observations
  72. EP 260329b: COLIBRÍ optical observations
  73. EP260329a: Optical upper limit with Kinder observations
  74. EP260329b: LCO optical observations of the counterpart
  75. EP260329b: Einstein Probe detection of an X-ray transient
  76. EP260329a: Einstein Probe detection of an X-ray transient
  77. EP-WXT trigger 01709259209: TRT optical counterpart detection
  78. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  79. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  80. EP260327a: SVOM/VT optical upper limits
  81. EP260327a: WINTER J-band upper limit
  82. EP260327a: COLIBRÍ optical upper limits
  83. EP260327a: Gemini-North optical upper limits
  84. EP260324a: GROWTH-India Telescope optical observation
  85. EP260327a: Einstein Probe detection of an X-ray transient
  86. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  87. The EP-WXT trigger 01709259173 is likely a flaring star
  88. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  89. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  90. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  91. EP260321a: JinShan near-infrared observations
  92. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  93. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  94. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  95. The EP-WXT trigger 01709259112 is likely a flaring star
  96. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  97. EP260321a: COLIBRÍ further optical observations and brightening
  98. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  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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