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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"

4252 results found.

  1. GRB 260921A: NuSTAR detection of prompt emission
  2. GRB 260921A: SVOM/GRM observation
  3. GRB 260922A: COLIBRÍ Confirmation of the Optical Counterpart
  4. Konus-Wind detection of GRB 260921A (possible merger-origin)
  5. Fermi-LAT Gamma-ray Observations of IceCube-260805A
  6. GRB 260921A: AstroSat CZTI detection
  7. GRB 260921A: Fermi GBM Observation
  8. GRB 260921A: Swift detection of a burst
  9. GRB 260921A: Fermi GBM Final Real-time Localization
  10. EP260920b: COLIBRÍ optical observations
  11. EP Alert 260921.01: Global MASTER-Net observations report
  12. The EP-WXT trigger 01709318491 is likely a flaring star
  13. IPN triangulation of GRB 260810A
  14. EP Alert 260917.32: Global MASTER-Net observations report
  15. Fermi trigger No 811264269: Global MASTER-Net observations report
  16. EP Alert 260914.53: Global MASTER-Net observations report
  17. GRB 260914A: SVOM/C-GFT optical observations
  18. GRB 260914A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  19. SVOM GRB260914.47: Global MASTER-Net observations report
  20. Fermi trigger No 810554827: Global MASTER-Net observations report
  21. The EP-WXT trigger 01709302592 is likely a flaring star
  22. NuSTAR Transient 260828: SOAR Optical Upper Limits
  23. GRB 260829A: AstroSat CZTI detection
  24. EP260830a: Global MASTER-Net observations report
  25. GRB 260829A: Fermi GBM Detection
  26. GRB 260829A: BALROG localization (Fermi Trigger 809676494 / GRB 260829256)
  27. GRB 260829A: Fermi GBM Final Real-time Localization
  28. Fermi GBM trigger 809666623/260829141 is not a GRB
  29. MAXI GRB260827.40: Global MASTER-Net observations report
  30. IceCube Alert 260825A: Global MASTER-Net observations report
  31. GRB 260818B: VLA radio observations
  32. GRB 260818B: SVOM/GRM observation
  33. EP260812a: AZT-22 optical upper limit
  34. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  35. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  36. GRB 260809A: NOT optical observations
  37. EP260809a: J-band upper limit with WINTER
  38. GRB 260808B: LCO optical observations
  39. Fermi GRB 260808A: Global MASTER-Net observations report
  40. SN 2026stf / GRB 260708A: ATLAS forced photometry
  41. Fermi GRB 260802B: Global MASTER-Net observations report
  42. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  43. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  44. EP260723a: SVOM/VT optical observation
  45. Fermi GRB 260718A: Global MASTER-Net observations report
  46. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  47. EP260711a: EP-FXT follow-up observation
  48. GRB 260629A: AstroSat CZTI detection
  49. GRB 260703A: Fermi GBM Final Localization
  50. Fermi trigger No 804552016: Global MASTER-Net observations report
  51. GRB 260629A: Fermi GBM Final Real-time Localization
  52. Fermi GRB 260628A: Global MASTER-Net observations report
  53. EP260623a: TNG NIR afterglow detection
  54. EP260623a: WINTER J-band observations
  55. GRB 260619A: SVOM possible detection of a faint burst
  56. GRB 260506B: cubesat Avion detection
  57. GRB 260429A: cubesat Avion detection
  58. GRB 260610B: further Liverpool Telescope optical observations
  59. GRB 260610B / AT2026owq: GRANDMA optical observations
  60. EP260605a: COLIBRÍ optical upper limits
  61. EP260610b: Liverpool Telescope optical upper limits
  62. GRB 260610B / AT2026owq: SVOM/VT optical observations
  63. GRB 260604C: SVOM/C-GFT upper limit
  64. EP260602a: COLIBRÍ optical observations
  65. SVOM GRB260603.23: Global MASTER-Net observations report
  66. Fermi GRB 260602B: Global MASTER-Net observations report
  67. Fermi GRB 260602B: Global MASTER-Net observations report
  68. GRB 260602A: Fermi GBM Final Real-time Localization
  69. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  70. AT2026nik: EP-FXT X-ray counterpart
  71. Fermi trigger No 801900520: Global MASTER-Net observations report
  72. EP260527a/GRB 260527A: further FTW optical and NIR observations
  73. GRB 260527A / EP260527a: VLA radio detection
  74. GRB 260529A: GOTO tentative optical afterglow candidate
  75. Fermi GRB 260529A: Global MASTER-Net observations report
  76. GRB 260529A: Fermi GBM Final Real-time Localization
  77. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  78. EP260527a: SVOM/VT optical observation
  79. Fermi trigger No 801580882: Global MASTER-Net observations report
  80. EP260526.405: COLIBRÍ optical upper limits
  81. EP-WXT 01709266106: NOT optical upper limits
  82. GRB 260515A: OHP/T193 optical observations
  83. SVOM GRB 260515A: Global MASTER-Net observations report
  84. GRB 260511B: Mephisto multi-band optical followup
  85. Fermi GRB 260514A: Global MASTER-Net observations report
  86. GRB 260511B SVOM/C-GFT optical counterpart detection
  87. Fermi GRB 260511A: Global MASTER-Net observations report
  88. GRB 260510C: MAXI/GSC detection
  89. EP260509a: Global MASTER-Net observations report
  90. SVOM GRB 260509A: MASTER-OAFA optical observation
  91. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  92. SVOM GRB 260504B: MASTER-OAFA optical observations
  93. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  94. IPN triangulation of a bright burst from SGR 1E1841-045
  95. GRB 260429B / EP260429a: AstroSat CZTI detection
  96. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  97. GRB 260429A: Fermi GBM Detection
  98. EP260429a: EP-WXT detection of a fast X-ray transient
  99. GRB 260429A: Fermi GBM Final Real-time Localization
  100. Fermi GRB 260428A: Global MASTER-Net observations report

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