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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.

Advanced Search Examples (click to copy):

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

2974 results found.

  1. GRB 260511B: further SAO RAS optical observations
  2. GRB 260511A: NuSTAR detection of prompt emission
  3. GRB 260511A: KAIT optical afterglow observations
  4. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  5. EP260507a: GOTO optical counterpart detection
  6. EP260507a: Einstein Probe detection of an X-ray transient
  7. Fermi GRB 260506A: Global MASTER-Net observations report
  8. SVOM GRB 260504B: MASTER-OAFA optical observations
  9. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  10. EP260430a: Global MASTER-Net observations report
  11. Fermi GRB 260421C: Global MASTER-Net observations report
  12. Fermi GRB 260421B: Global MASTER-Net observations report
  13. Fermi GRB 260417B: Global MASTER-Net observations report
  14. EP260417a: Global MASTER-Net observations report
  15. Fermi GRB 260417A: Global MASTER-Net observations report
  16. EP260416a: Global MASTER-Net observations report
  17. Fermi trigger No 797912738: Global MASTER-Net observations report
  18. GRB 260411B: GOTO optical counterpart candidate
  19. EP260409a: Global MASTER-Net observations report
  20. GRB 260404A: Fermi GBM Final Localization
  21. EP260403a: Mephisto optical upper limits
  22. EP260405a: Global MASTER-Net observations report
  23. Fermi trigger No 797039833: Global MASTER-Net observations report
  24. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  25. GRB 260330B: SVOM/ECLAIRs refined analysis
  26. GRB 260330B: SVOM/VT optical candidate
  27. GRB 260402B: GECAM-B observation
  28. GRB 260402B: Fermi GBM Final Real-time Localization
  29. EP260329b: Mondy and Assy-Turgen optical upper limits
  30. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  31. EP260321a :Xinglong optical observations
  32. GRB 260321A: SVOM/ECLAIRs refined analysis
  33. Fermi GBM Sub-Threshold Detection of GRB 260330B
  34. GRB 260330B: SVOM detection of a burst
  35. EP260327a: Global MASTER-Net observations report
  36. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  37. IPN triangulation of GRB 260316B
  38. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  39. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  40. Fermi GRB 260323A: Global MASTER-Net observations report
  41. GRB 260321A: SVOM/VT optical upper limits
  42. GRB 260310A: continued optical observation at Mondy
  43. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  44. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  45. Fermi trigger No 795185313: Global MASTER-Net observations report
  46. IceCube Alert 260315A: Global MASTER-Net observations report
  47. Fermi GRB 260313A: Global MASTER-Net observations report
  48. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  49. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  50. GRB 260310A: Fermi GBM Observation
  51. Fermi GRB 260311B: Global MASTER-Net observations report
  52. GRB 260312A: Swift detection of a burst
  53. GRB 260311B: Fermi GBM Final Real-time Localization
  54. GRB 260310A: AstroSat CZTI detection of a long burst
  55. Fermi GRB 260310A: Global MASTER-Net observations report
  56. GRB 260208A: radio detection with the VLA
  57. GRB 260310A: Fermi GBM Final Real-time Localization
  58. Fermi GRB 260307A: Global MASTER-Net observations report
  59. Fermi GRB 260305A: Global MASTER-Net observations report
  60. EP260227a: Global MASTER-Net observations report
  61. Konus-Wind detection of GRB 260226A
  62. GRB 260225A: SVOM detection of a burst
  63. EP260213a: Mephisto optical upper limits
  64. EP260223a: COLIBRÍ optical upper limits
  65. EP260221a: Global MASTER-Net observations report
  66. Fermi GRB 260221A: Global MASTER-Net observations report
  67. GRB 260216A: Fermi GBM Final Real-time Localization
  68. EP260214b: Einstein Probe detection of a fast X-ray transient
  69. GRB 260210A: SVOM/GRM observation
  70. Fermi GRB 260210C: Global MASTER-Net observations report
  71. EP260210a: Global MASTER-Net observations report
  72. EP260210a: refined analysis of the EP-FXT observation
  73. EP260210a: Optical upper limits with Kinder observations
  74. EP260210a: SVOM/VT optical upper limit
  75. Fermi GRB 260209A: Global MASTER-Net observations report
  76. GRB 260208B: SVOM/VT optical candidate
  77. GRB 260209A: Fermi GBM Final Real-time Localization
  78. GRB 260208A: SVOM/VT optical observation
  79. Fermi GRB 260208A: Global MASTER-Net observations report
  80. GRB 260204A : MASTER Global robotic net optical observations
  81. GRB 260131A: NOT spectroscopic redshift z = 1.434
  82. Fermi GRB 260129A: Global MASTER-Net observations report
  83. GRB 260129B: Fermi GBM Final Localization
  84. GRB 260127B: GOTO candidate optical counterpart
  85. GRB 260122B: Swift-BAT refined analysis
  86. GRB 260120B: Swift-BAT refined analysis
  87. SVOM GRB260121.06: Global MASTER-Net observations report
  88. Fermi trigger No 790570272: Global MASTER-Net observations report
  89. EP260119a: Global MASTER-Net observations report
  90. The EP-WXT trigger 01709251266 is likely a flaring star
  91. EP260110a: SVOM/C-GFT upper limit
  92. GRB 260104A: Swift-BAT refined analysis
  93. GRB 260101A: Swift-BAT refined analysis
  94. Fermi GRB 260107A: Global MASTER-Net observations report
  95. GRB 260107A: Fermi GBM Final Real-time Localization
  96. Fermi GRB 260105A: Global MASTER-Net observations report
  97. EP260105a: Global MASTER-Net observations report
  98. GRB 260104C: Fermi GBM Final Real-time Localization
  99. Fermi GRB 260104B: Global MASTER-Net observations report
  100. SVOM GRB260103.08: Global MASTER-Net observations report

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