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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

21769 results found.

  1. EP260417a: TRT optical counterpart detection
  2. EP260417a: Einstein Probe detection of an X-ray transient
  3. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  4. EP260417b: Einstein Probe detection of a fast X-ray transient
  5. EP260416a: KAIT optical upper limit
  6. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  7. EP260416a: WFST optical observations and rebrightening
  8. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  9. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  10. EP260416a: COLIBRÍ optical counterpart candidate
  11. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  12. EP260416a: Einstein Probe detection of an X-ray transient
  13. GOTO26djh/AT2026jpw : MASTER OT observation
  14. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  15. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  16. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  17. EP260321a: CMO SAI J,K observations
  18. Konus-Wind detection of GRB 260410A (short/hard)
  19. GRB 260411B: Fermi-LAT detection
  20. GRB 260412A: SVOM detection of a long burst
  21. GRB 260411B: COLIBRÍ optical observations
  22. GRB260411B: 3.6m DOT optical observation
  23. GRB 260411A: SVOM/GRM observation
  24. GRB 260411B: SVOM/GRM observation of a long burst
  25. GRB 260411B: GOTO optical counterpart candidate
  26. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  27. GRB 260410A: COLIBRÍ optical upper limit
  28. EP-WXT01709259790: Optical Upper limits with kinder observations
  29. EP-WXT01709259790: Xinglong optical upper limit
  30. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  31. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  32. EP260409a: COLIBRÍ optical upper limits
  33. EP260409a: Einstein Probe detection of an X-ray transient
  34. EP260321a: VLA radio detection
  35. GRB 260402A: SVOM/ECLAIRs refined analysis
  36. EP260402a / GRB 260402A: Mephisto optical upper limits
  37. EP-WXT01709259586: Xinglong optical upper limit
  38. EP260403a: Mephisto optical upper limits
  39. EP260402a/GRB 260402A: Xinglong optical upper limit
  40. EP260321a: uGMRT observations
  41. EP260405a: GMOS-N optical upper limits
  42. EP260405a: Einstein Probe detection of a fast X-ray transient
  43. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  44. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  45. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  46. GRB 260330B: SVOM/VT further optical observation
  47. EP260403a: LCO optical observations of the counterpart
  48. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  49. EP260403a: LCO optical counterpart detection
  50. EP260403a: COLIBRÍ optical counterpart candidate
  51. GRB 260330B: SVOM/VT optical candidate
  52. EP260403a: Einstein Probe detection of an X-ray transient
  53. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  54. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  55. EP260324A / AT 2026hir: COLIBRÍ optical observations
  56. GRB 260402A: WINTER J-band upper limit
  57. GRB260402A: GROWTH-India Telescope optical upper limit
  58. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  59. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  60. GRB 260401A: SVOM/GRM observation
  61. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  62. GRB 260402A: Kilonova-Catcher optical upper limit
  63. GRB 260402A: MASTER optical observations
  64. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  65. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  66. GRB 260402A: SVOM detection of a burst
  67. EP260329b: Mondy and Assy-Turgen optical upper limits
  68. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  69. EP260321a :Xinglong optical observations
  70. EP260327a: Xinglong optical upper limit
  71. GRB 260330B: SVOM/VT optical upper limits
  72. Konus-Wind detection of GRB 260320A
  73. Konus-Wind detection of GRB 260316B
  74. GRB 260321A: SVOM/ECLAIRs refined analysis
  75. EP260329b: J-band upper limits with WINTER
  76. EP260329a: J-band upper limit with WINTER
  77. GRB 260330B: LCO optical upper limits
  78. GRB 260330B: SVOM detection of a burst
  79. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  80. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  81. EP260329a: COLIBRÍ optical upper limit
  82. EP260329a: EP-FXT follow up observation
  83. EP260329a: NOT optical counterpart candidate
  84. EP260329b: Optical follow-up with Kinder observations
  85. EP 260329b: COLIBRÍ optical observations
  86. EP260329a: Optical upper limit with Kinder observations
  87. EP260329b: LCO optical observations of the counterpart
  88. EP260329b: Einstein Probe detection of an X-ray transient
  89. EP260329a: Einstein Probe detection of an X-ray transient
  90. EP-WXT trigger 01709259209: TRT optical counterpart detection
  91. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  92. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  93. EP260327a: SVOM/VT optical upper limits
  94. EP260327a: WINTER J-band upper limit
  95. EP260327a: COLIBRÍ optical upper limits
  96. GRB 260327A: AstroSat CZTI detection of a long burst
  97. EP260327a: Gemini-North optical upper limits
  98. EP260324a: GROWTH-India Telescope optical observation
  99. EP260327a: Einstein Probe detection of an X-ray transient
  100. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova

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