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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"

20366 results found.

  1. EP260417b: Einstein Probe detection of a fast X-ray transient
  2. EP260416a: KAIT optical upper limit
  3. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  4. EP260416a: WFST optical observations and rebrightening
  5. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  6. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  7. EP260416a: COLIBRÍ optical counterpart candidate
  8. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  9. EP260416a: Einstein Probe detection of an X-ray transient
  10. GOTO26djh/AT2026jpw : MASTER OT observation
  11. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  12. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  13. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  14. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  15. EP260321a: CMO SAI J,K observations
  16. GRB 260412A: Insight-HXMT/HE detection
  17. GRB 260412A: GECAM-B observation of a long burst
  18. GRB 260411B: Fermi-LAT detection
  19. GRB 260411B: COLIBRÍ optical observations
  20. GRB260411B: 3.6m DOT optical observation
  21. GRB 260411A: SVOM/GRM observation
  22. GRB 260411B: SVOM/GRM observation of a long burst
  23. GRB 260411B: Fermi GBM Detection
  24. GRB 260411B: GOTO optical counterpart candidate
  25. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  26. GRB 260410A: COLIBRÍ optical upper limit
  27. EP-WXT01709259790: Optical Upper limits with kinder observations
  28. EP-WXT01709259790: Xinglong optical upper limit
  29. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  30. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  31. EP260409a: COLIBRÍ optical upper limits
  32. EP260409a: Einstein Probe detection of an X-ray transient
  33. EP260321a: VLA radio detection
  34. GRB 260402A: SVOM/ECLAIRs refined analysis
  35. EP260402a / GRB 260402A: Mephisto optical upper limits
  36. EP-WXT01709259586: Xinglong optical upper limit
  37. EP260403a: Mephisto optical upper limits
  38. EP260402a/GRB 260402A: Xinglong optical upper limit
  39. GRID detection of GRB 260401A
  40. EP260405a: GMOS-N optical upper limits
  41. EP260405a: Einstein Probe detection of a fast X-ray transient
  42. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  43. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  44. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  45. GRB 260330B: SVOM/VT further optical observation
  46. GRB 260330B: SVOM/ECLAIRs refined analysis
  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. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  54. GRB 260403A: AstroSat CZTI detection
  55. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  56. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  57. GRB 260402C: AstroSat CZTI detection of a long burst
  58. EP260324A / AT 2026hir: COLIBRÍ optical observations
  59. GRB 260402A: WINTER J-band upper limit
  60. GRB260402A: GROWTH-India Telescope optical upper limit
  61. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  62. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  63. GRB 260401A: SVOM/GRM observation
  64. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  65. GRB 260402A: Kilonova-Catcher optical upper limit
  66. GRB 260402A: MASTER optical observations
  67. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  68. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  69. GRB 260402A: SVOM detection of a burst
  70. EP260329b: Mondy and Assy-Turgen optical upper limits
  71. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  72. EP260321a :Xinglong optical observations
  73. EP260327a: Xinglong optical upper limit
  74. GRB 260330B: SVOM/VT optical upper limits
  75. GRB 260321A: SVOM/ECLAIRs refined analysis
  76. EP260329b: J-band upper limits with WINTER
  77. EP260329a: J-band upper limit with WINTER
  78. GRB 260310A: VLA Multi-frequency Radio Observations
  79. GRB 260330B: LCO optical upper limits
  80. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  81. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  82. EP260329a: COLIBRÍ optical upper limit
  83. EP260329a: EP-FXT follow up observation
  84. EP260329a: NOT optical counterpart candidate
  85. EP260329b: Optical follow-up with Kinder observations
  86. EP 260329b: COLIBRÍ optical observations
  87. EP260329a: Optical upper limit with Kinder observations
  88. EP260329b: LCO optical observations of the counterpart
  89. EP260329b: Einstein Probe detection of an X-ray transient
  90. EP260329a: Einstein Probe detection of an X-ray transient
  91. EP-WXT trigger 01709259209: TRT optical counterpart detection
  92. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  93. GRID detection of GRB 260326A
  94. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  95. EP260327a: SVOM/VT optical upper limits
  96. EP260327a: WINTER J-band upper limit
  97. EP260327a: COLIBRÍ optical upper limits
  98. GRB 260327A: AstroSat CZTI detection of a long burst
  99. EP260327a: Gemini-North optical upper limits
  100. EP260324a: GROWTH-India Telescope optical observation

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