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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"

2975 results found.

  1. EP260514a: Global MASTER-Net observations report
  2. GRB 260511B: further SAO RAS optical observations
  3. GRB 260511A: NuSTAR detection of prompt emission
  4. GRB 260511A: KAIT optical afterglow observations
  5. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  6. EP260507a: GOTO optical counterpart detection
  7. EP260507a: Einstein Probe detection of an X-ray transient
  8. Fermi GRB 260506A: Global MASTER-Net observations report
  9. SVOM GRB 260504B: MASTER-OAFA optical observations
  10. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  11. EP260430a: Global MASTER-Net observations report
  12. Fermi GRB 260421C: Global MASTER-Net observations report
  13. Fermi GRB 260421B: Global MASTER-Net observations report
  14. Fermi GRB 260417B: Global MASTER-Net observations report
  15. EP260417a: Global MASTER-Net observations report
  16. Fermi GRB 260417A: Global MASTER-Net observations report
  17. EP260416a: Global MASTER-Net observations report
  18. Fermi trigger No 797912738: Global MASTER-Net observations report
  19. GRB 260411B: GOTO optical counterpart candidate
  20. EP260409a: Global MASTER-Net observations report
  21. GRB 260404A: Fermi GBM Final Localization
  22. EP260403a: Mephisto optical upper limits
  23. EP260405a: Global MASTER-Net observations report
  24. Fermi trigger No 797039833: Global MASTER-Net observations report
  25. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  26. GRB 260330B: SVOM/ECLAIRs refined analysis
  27. GRB 260330B: SVOM/VT optical candidate
  28. GRB 260402B: GECAM-B observation
  29. GRB 260402B: Fermi GBM Final Real-time Localization
  30. EP260329b: Mondy and Assy-Turgen optical upper limits
  31. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  32. EP260321a :Xinglong optical observations
  33. GRB 260321A: SVOM/ECLAIRs refined analysis
  34. Fermi GBM Sub-Threshold Detection of GRB 260330B
  35. GRB 260330B: SVOM detection of a burst
  36. EP260327a: Global MASTER-Net observations report
  37. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  38. IPN triangulation of GRB 260316B
  39. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  40. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  41. Fermi GRB 260323A: Global MASTER-Net observations report
  42. GRB 260321A: SVOM/VT optical upper limits
  43. GRB 260310A: continued optical observation at Mondy
  44. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  45. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  46. Fermi trigger No 795185313: Global MASTER-Net observations report
  47. IceCube Alert 260315A: Global MASTER-Net observations report
  48. Fermi GRB 260313A: Global MASTER-Net observations report
  49. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  50. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  51. GRB 260310A: Fermi GBM Observation
  52. Fermi GRB 260311B: Global MASTER-Net observations report
  53. GRB 260312A: Swift detection of a burst
  54. GRB 260311B: Fermi GBM Final Real-time Localization
  55. GRB 260310A: AstroSat CZTI detection of a long burst
  56. Fermi GRB 260310A: Global MASTER-Net observations report
  57. GRB 260208A: radio detection with the VLA
  58. GRB 260310A: Fermi GBM Final Real-time Localization
  59. Fermi GRB 260307A: Global MASTER-Net observations report
  60. Fermi GRB 260305A: Global MASTER-Net observations report
  61. EP260227a: Global MASTER-Net observations report
  62. Konus-Wind detection of GRB 260226A
  63. GRB 260225A: SVOM detection of a burst
  64. EP260213a: Mephisto optical upper limits
  65. EP260223a: COLIBRÍ optical upper limits
  66. EP260221a: Global MASTER-Net observations report
  67. Fermi GRB 260221A: Global MASTER-Net observations report
  68. GRB 260216A: Fermi GBM Final Real-time Localization
  69. EP260214b: Einstein Probe detection of a fast X-ray transient
  70. GRB 260210A: SVOM/GRM observation
  71. Fermi GRB 260210C: Global MASTER-Net observations report
  72. EP260210a: Global MASTER-Net observations report
  73. EP260210a: refined analysis of the EP-FXT observation
  74. EP260210a: Optical upper limits with Kinder observations
  75. EP260210a: SVOM/VT optical upper limit
  76. Fermi GRB 260209A: Global MASTER-Net observations report
  77. GRB 260208B: SVOM/VT optical candidate
  78. GRB 260209A: Fermi GBM Final Real-time Localization
  79. GRB 260208A: SVOM/VT optical observation
  80. Fermi GRB 260208A: Global MASTER-Net observations report
  81. GRB 260204A : MASTER Global robotic net optical observations
  82. GRB 260131A: NOT spectroscopic redshift z = 1.434
  83. Fermi GRB 260129A: Global MASTER-Net observations report
  84. GRB 260129B: Fermi GBM Final Localization
  85. GRB 260127B: GOTO candidate optical counterpart
  86. GRB 260122B: Swift-BAT refined analysis
  87. GRB 260120B: Swift-BAT refined analysis
  88. SVOM GRB260121.06: Global MASTER-Net observations report
  89. Fermi trigger No 790570272: Global MASTER-Net observations report
  90. EP260119a: Global MASTER-Net observations report
  91. The EP-WXT trigger 01709251266 is likely a flaring star
  92. EP260110a: SVOM/C-GFT upper limit
  93. GRB 260104A: Swift-BAT refined analysis
  94. GRB 260101A: Swift-BAT refined analysis
  95. Fermi GRB 260107A: Global MASTER-Net observations report
  96. GRB 260107A: Fermi GBM Final Real-time Localization
  97. Fermi GRB 260105A: Global MASTER-Net observations report
  98. EP260105a: Global MASTER-Net observations report
  99. GRB 260104C: Fermi GBM Final Real-time Localization
  100. Fermi GRB 260104B: Global MASTER-Net observations report

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