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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"

3797 results found.

  1. EP260405a: Global MASTER-Net observations report
  2. Fermi trigger No 797039833: Global MASTER-Net observations report
  3. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  4. GRB 260330B: SVOM/ECLAIRs refined analysis
  5. GRB 260330B: SVOM/VT optical candidate
  6. GRB 260402B: GECAM-B observation
  7. GRB 260402B: Fermi GBM Final Real-time Localization
  8. GRB 260401A: SVOM/GRM observation
  9. GRB 260401A: GECAM-B observation
  10. GRB 260401A: Fermi GBM Observation
  11. GRB 260401A: NuSTAR detection of prompt emission
  12. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  13. GRB 260401A: MAXI/GSC detection
  14. EP260329b: Mondy and Assy-Turgen optical upper limits
  15. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  16. EP260321a :Xinglong optical observations
  17. GRB 260321A: SVOM/ECLAIRs refined analysis
  18. Fermi GBM Sub-Threshold Detection of GRB 260330B
  19. GRB 260330B: SVOM detection of a burst
  20. EP260327a: Global MASTER-Net observations report
  21. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  22. IPN triangulation of GRB 260316B
  23. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  24. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  25. Fermi GRB 260323A: Global MASTER-Net observations report
  26. GRB 260321A: SVOM/VT optical upper limits
  27. GRB 260310A: continued optical observation at Mondy
  28. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  29. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  30. Fermi trigger No 795185313: Global MASTER-Net observations report
  31. IceCube Alert 260315A: Global MASTER-Net observations report
  32. Fermi GRB 260313A: Global MASTER-Net observations report
  33. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  34. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  35. GRB 260310A: Fermi GBM Observation
  36. Fermi GRB 260311B: Global MASTER-Net observations report
  37. GRB 260312A: Swift detection of a burst
  38. GRB 260311B: Fermi GBM Final Real-time Localization
  39. GRB 260310A: AstroSat CZTI detection of a long burst
  40. Fermi GRB 260310A: Global MASTER-Net observations report
  41. GRB 260208A: radio detection with the VLA
  42. GRB 260310A: Fermi GBM Final Real-time Localization
  43. Fermi GRB 260307A: Global MASTER-Net observations report
  44. Fermi GRB 260305A: Global MASTER-Net observations report
  45. EP260227a: Global MASTER-Net observations report
  46. Konus-Wind detection of GRB 260226A
  47. GRB 260225A: SVOM detection of a burst
  48. EP260213a: Mephisto optical upper limits
  49. EP260223a: COLIBRÍ optical upper limits
  50. EP260221a: Global MASTER-Net observations report
  51. Fermi GRB 260221A: Global MASTER-Net observations report
  52. GRB 260216A: Fermi GBM Final Real-time Localization
  53. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  54. EP260214b: Einstein Probe detection of a fast X-ray transient
  55. GRB 260210A: SVOM/GRM observation
  56. Fermi GRB 260210C: Global MASTER-Net observations report
  57. EP260210a: Global MASTER-Net observations report
  58. EP260210a: refined analysis of the EP-FXT observation
  59. EP260210a: Optical upper limits with Kinder observations
  60. EP260210a: SVOM/VT optical upper limit
  61. Fermi GRB 260209A: Global MASTER-Net observations report
  62. GRB 260208B: SVOM/VT optical candidate
  63. GRB 260209A: Fermi GBM Final Real-time Localization
  64. GRB 260208A: SVOM/VT optical observation
  65. Fermi GRB 260208A: Global MASTER-Net observations report
  66. GRB 260206A: Swift-XRT observations
  67. GRB 260206A: Tiled Swift observations
  68. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  69. GRB 260204A : MASTER Global robotic net optical observations
  70. GRID detection of GRB 260131A/B
  71. GRB 260131A/B: EP/FXT X-ray afterglow detection
  72. GRB 260131A: NOT spectroscopic redshift z = 1.434
  73. Konus-Wind detection of GRB 260131A/B
  74. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  75. GRB 260131A/B: Fermi GBM Observation
  76. GRB 260131B: MAXI/GSC detection
  77. Fermi GRB 260129A: Global MASTER-Net observations report
  78. GRB 260129B: Fermi GBM Final Localization
  79. GRB 260127B: GOTO candidate optical counterpart
  80. GRB 260122B: Swift-BAT refined analysis
  81. GRB 260120B: Swift-BAT refined analysis
  82. SVOM GRB260121.06: Global MASTER-Net observations report
  83. Fermi trigger No 790570272: Global MASTER-Net observations report
  84. EP260119a: Global MASTER-Net observations report
  85. The EP-WXT trigger 01709251266 is likely a flaring star
  86. EP260110a: SVOM/C-GFT upper limit
  87. GRB 260104A: Swift-BAT refined analysis
  88. GRB 260101A: Swift-BAT refined analysis
  89. Fermi GRB 260107A: Global MASTER-Net observations report
  90. GRB 260107A: Fermi GBM Final Real-time Localization
  91. Fermi GRB 260105A: Global MASTER-Net observations report
  92. EP260105a: Global MASTER-Net observations report
  93. GRB 260104C: Fermi GBM Final Real-time Localization
  94. Fermi GRB 260104B: Global MASTER-Net observations report
  95. SVOM GRB260103.08: Global MASTER-Net observations report
  96. EP260101a: Global MASTER-Net observations report
  97. GRB 260101A: Swift detection of a burst with an optical counterpart
  98. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  99. Fermi GRB 251228A: Global MASTER-Net observations report
  100. SVOM GRB251227.07: Global MASTER-Net observations report

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