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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"

23413 results found.

  1. GRB 260511A: KAIT optical afterglow observations
  2. GRB 260511A: LCO optical afterglow detection
  3. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  4. GRB 260511A: TRT optical counterpart detection
  5. GRB 260511A: SVOM detection of a bright burst
  6. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  7. GRB 260510B: SVOM/VT optical upper limits
  8. GRB 260510C: SVOM/VT optical upper limits
  9. Fermi GBM Sub-Threshold Detection of GRB 260510B
  10. GRB 260510C: SVOM detection of a burst
  11. GRB 260510B: LCO optical upper limits
  12. EP260509a: Einstein Probe detection of an X-ray transient
  13. GRB 260509A: Liverpool Telescope optical observations
  14. GRB 260510B: SVOM detection of a burst
  15. GRB 260509A: LCO optical observations
  16. SVOM GRB 260509A: MASTER-OAFA optical observation
  17. GRB 260509A: KAIT optical observations
  18. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  19. GRB 260509A: SVOM/VT optical candidate with VHF data
  20. GRB 260509A: LCO optical counterpart detection
  21. GRB 260509A: SVOM detection of a burst
  22. GRB 260506B: AstroSat CZTI detection
  23. EP260507a: REM optical/NIR observations
  24. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  25. EP260507a: COLIBRÍ optical observations
  26. EP260507a: NOT optical observations
  27. EP260507a: further Liverpool Telescope observations
  28. EP260507a: Liverpool Telescope optical upper limits
  29. EP260507a: GOTO optical counterpart detection
  30. EP260507a: TRT optical counterpart detection
  31. EP260507a: Kinder optical counterpart candidate
  32. EP260507a: LCO optical counterpart
  33. EP260507a: Einstein Probe detection of an X-ray transient
  34. GRB 260503A: GECAM-B observation of a burst
  35. GRB 260430B: Glowbug gamma-ray detection
  36. GRB 260421B: radio observation with the VLA
  37. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  38. GRB 260502A: SVOM/GRM observation of a short GRB
  39. GRB 260503A: SVOM/GRM observation of a GRB
  40. GRB 260504B: REM optical/NIR observations
  41. IPN triangulation of GRB 260429A
  42. IPN triangulation of GRB 260428A
  43. GRB 260504B: LCO z-band upper limit
  44. SVOM GRB 260504B: MASTER-OAFA optical observations
  45. GRB 260504B: SVOM detection of a short burst
  46. GRB 260503A: Fermi GBM Final Real-time Localization
  47. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  48. IPN triangulation of a bright burst from SGR 1E1841-045
  49. GRB 260429B / EP260429a: AstroSat CZTI detection
  50. EP260502a: BOOTES-7: early optical upper limit
  51. EP260502a: Las Cumbres upper limit
  52. EP260502a: Einstein Probe detection of an X-ray transient
  53. GRB 260429A: SVOM/GRM observation of a short burst
  54. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  55. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  56. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  57. EP260429a: LCO optical upper limits
  58. EP260430a: LCO optical upper limits
  59. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  60. EP260430a: Einstein Probe detection of an X-ray transient
  61. EP260429a: EP-WXT detection of a fast X-ray transient
  62. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  63. GRB 260428A: AstroSat CZTI detection
  64. EP260416a: Mondy and Terskol optical upper limits
  65. GRB 260424B: Glowbug gamma-ray detection of a short burst
  66. GRB 260424B: COLIBRÍ optical upper limit
  67. Konus-Wind detection of GRB 260424B
  68. IPN triangulation of GRB 260424B (short)
  69. GRB 260401A: cubesat Avion detection
  70. GRB 260424A: AstroSat CZTI detection of a long burst
  71. EP260321a: Upper limits from ATCA radio observations
  72. GRB 260421B: Kilonova-Catcher optical afterglow detection
  73. EP260416a: Mondy optical observations
  74. GRB 260421B: 3.6m DOT optical observation
  75. EP260416a: ZTSh R band observations
  76. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  77. GRB 260421B: SVOM/GRM observation
  78. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  79. GOTO26djh/AT2026jpw: ATCA radio detection
  80. GRB 260421B: J-band upper limit with WINTER
  81. GRB 260421B: LCO optical counterpart detection
  82. GOTO26djh/AT2026jpw: radio detection at 15GHz
  83. GRB 260421B: SVOM/VT optical observations
  84. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  85. GRB 260310A: Late-time Chandra X-ray Detection
  86. EP260416a: 1.3m DFOT optical observation
  87. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  88. GRB 260421B: LCO optical afterglow confirmation
  89. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  90. GRB 260421B: TRT optical counterpart detection
  91. GRB 260421B: SVOM detection of a long burst
  92. EP260321a: VLA radio follow-up
  93. GRB 260412A: LCOGT Optical Upper Limits
  94. EP260416a: Optical follow-up observations with Kinder
  95. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  96. GRB 260417A: SVOM/GRM observation
  97. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  98. EP260417a: GROWTH-India Telescope optical upper limit
  99. EP260417b: GROWTH-India Telescope optical upper limit
  100. EP260416a: Ondrejov D50 optical detection

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