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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').
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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"

11749 results found.

  1. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  2. EP260507a: Liverpool Telescope optical upper limits
  3. GRB 260507A: Fermi GBM Final Real-time Localization
  4. EP260507a: Kinder optical counterpart candidate
  5. EP260507a: Einstein Probe detection of an X-ray transient
  6. GRB 260504B: AstroSat CZTI detection
  7. IceCube Alert 260505A: Global MASTER-Net observations report
  8. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  9. Konus-Wind detection of GRB 260504B (short/hard)
  10. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  11. GRB 260430B: AstroSat CZTI detection of a long burst
  12. Konus-Wind detection of GRB 260415C
  13. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  14. Konus-Wind detection of GRB 260411C
  15. IPN triangulation of GRB 260429A
  16. IPN triangulation of GRB 260428A
  17. GRB 260503A: Fermi GBM Final Real-time Localization
  18. GRB 260429B / EP260429a: AstroSat CZTI detection
  19. EP260502a: Einstein Probe detection of an X-ray transient
  20. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  21. GRB 260424B: AstroSat CZTI detection
  22. GRB 260429A: Fermi GBM Detection
  23. Fermi GRB 260429A: Global MASTER-Net observations report
  24. EP260430a: Global MASTER-Net observations report
  25. EP260430a: Einstein Probe detection of an X-ray transient
  26. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  27. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  28. GRB 260428A: AstroSat CZTI detection
  29. Fermi GRB 260428A: Global MASTER-Net observations report
  30. EP260416a: Mondy and Terskol optical upper limits
  31. Konus-Wind detection of GRB 260424B
  32. GRB 260428A: Fermi GBM Final Real-time Localization
  33. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  34. GRB 260401A: cubesat Avion detection
  35. GRB 260424A: AstroSat CZTI detection of a long burst
  36. GRB 260421B: Kilonova-Catcher optical afterglow detection
  37. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  38. GRB 260421B: SVOM/ECLAIRs refined analysis
  39. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  40. GRB 260419A: AstroSat CZTI detection
  41. EP260416a: 1.3m DFOT optical observation
  42. Fermi GRB 260421B: Global MASTER-Net observations report
  43. Fermi GRB 260421A: Global MASTER-Net observations report
  44. GRB 260412A: LCOGT Optical Upper Limits
  45. EP260416a: Optical follow-up observations with Kinder
  46. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  47. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  48. GRB 260417A: SVOM/GRM observation
  49. Fermi trigger No 798275385: Global MASTER-Net observations report
  50. Fermi GRB 260417B: Global MASTER-Net observations report
  51. EP260416a: Ondrejov D50 optical detection
  52. GRB 260418B: Fermi GBM Final Real-time Localization
  53. EP260417a: Global MASTER-Net observations report
  54. Fermi GRB 260417A: Global MASTER-Net observations report
  55. Konus-Wind detection of GRB 260411B
  56. GRB 260417A: AstroSat CZTI detection
  57. IPN triangulation of GRB 260411B
  58. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  59. EP260417a: Einstein Probe detection of an X-ray transient
  60. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  61. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  62. EP260416a: COLIBRÍ optical counterpart candidate
  63. EP260416a: Global MASTER-Net observations report
  64. EP260416a: Einstein Probe detection of an X-ray transient
  65. GRB 260415B: NuSTAR detection of long prompt emission
  66. Fermi trigger No 797912738: Global MASTER-Net observations report
  67. EP260321a: CMO SAI J,K observations
  68. Konus-Wind detection of GRB 260410A (short/hard)
  69. GRB 260411B: Fermi-LAT detection
  70. GRB260411B: 3.6m DOT optical observation
  71. GRB 260411B: SVOM/GRM observation of a long burst
  72. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  73. EP-WXT01709259790: Optical Upper limits with kinder observations
  74. GRB 260410A: Fermi-LAT detection
  75. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  76. EP260409a: Einstein Probe detection of an X-ray transient
  77. GRB 260402A: SVOM/ECLAIRs refined analysis
  78. EP260402a / GRB 260402A: Mephisto optical upper limits
  79. EP260405a: Einstein Probe detection of a fast X-ray transient
  80. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  81. EP260403a: COLIBRÍ optical counterpart candidate
  82. EP260403a: Einstein Probe detection of an X-ray transient
  83. GRB 260403A: AstroSat CZTI detection
  84. GRB 260402C: AstroSat CZTI detection of a long burst
  85. EP260324A / AT 2026hir: COLIBRÍ optical observations
  86. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  87. GRB 260402A: SVOM detection of a burst
  88. Fermi GRB 260401A: Global MASTER-Net observations report
  89. GRB 260401A: MAXI/GSC detection
  90. EP260329b: Mondy and Assy-Turgen optical upper limits
  91. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  92. EP260327a: Xinglong optical upper limit
  93. EP260329b: GOTO detection of optical counterpart
  94. Konus-Wind detection of GRB 260320A
  95. Konus-Wind detection of GRB 260316B
  96. GRB 260330B: SVOM detection of a burst
  97. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  98. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  99. Fermi trigger No 796485221: Global MASTER-Net observations report
  100. EP260329b: Optical follow-up with Kinder observations

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