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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"

3040 results found.

  1. EP260327a: Global MASTER-Net observations report
  2. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  3. IPN triangulation of GRB 260316B
  4. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  5. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  6. Fermi GRB 260323A: Global MASTER-Net observations report
  7. GRB 260321A: SVOM/VT optical upper limits
  8. GRB 260310A: continued optical observation at Mondy
  9. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  10. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  11. Fermi trigger No 795185313: Global MASTER-Net observations report
  12. IceCube Alert 260315A: Global MASTER-Net observations report
  13. Fermi GRB 260313A: Global MASTER-Net observations report
  14. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  15. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  16. GRB 260310A: Fermi GBM Observation
  17. Fermi GRB 260311B: Global MASTER-Net observations report
  18. GRB 260312A: Swift detection of a burst
  19. GRB 260311B: Fermi GBM Final Real-time Localization
  20. GRB 260310A: AstroSat CZTI detection of a long burst
  21. Fermi GRB 260310A: Global MASTER-Net observations report
  22. GRB 260208A: radio detection with the VLA
  23. GRB 260310A: Fermi GBM Final Real-time Localization
  24. Fermi GRB 260307A: Global MASTER-Net observations report
  25. Fermi GRB 260305A: Global MASTER-Net observations report
  26. EP260227a: Global MASTER-Net observations report
  27. Konus-Wind detection of GRB 260226A
  28. GRB 260225A: SVOM detection of a burst
  29. EP260213a: Mephisto optical upper limits
  30. EP260223a: COLIBRÍ optical upper limits
  31. EP260221a: Global MASTER-Net observations report
  32. Fermi GRB 260221A: Global MASTER-Net observations report
  33. GRB 260216A: Fermi GBM Final Real-time Localization
  34. EP260214b: Einstein Probe detection of a fast X-ray transient
  35. GRB 260210A: SVOM/GRM observation
  36. Fermi GRB 260210C: Global MASTER-Net observations report
  37. EP260210a: Global MASTER-Net observations report
  38. EP260210a: refined analysis of the EP-FXT observation
  39. EP260210a: Optical upper limits with Kinder observations
  40. EP260210a: SVOM/VT optical upper limit
  41. Fermi GRB 260209A: Global MASTER-Net observations report
  42. GRB 260208B: SVOM/VT optical candidate
  43. GRB 260209A: Fermi GBM Final Real-time Localization
  44. GRB 260208A: SVOM/VT optical observation
  45. Fermi GRB 260208A: Global MASTER-Net observations report
  46. GRB 260204A : MASTER Global robotic net optical observations
  47. GRB 260131A: NOT spectroscopic redshift z = 1.434
  48. Fermi GRB 260129A: Global MASTER-Net observations report
  49. GRB 260129B: Fermi GBM Final Localization
  50. GRB 260127B: GOTO candidate optical counterpart
  51. GRB 260122B: Swift-BAT refined analysis
  52. GRB 260120B: Swift-BAT refined analysis
  53. SVOM GRB260121.06: Global MASTER-Net observations report
  54. Fermi trigger No 790570272: Global MASTER-Net observations report
  55. EP260119a: Global MASTER-Net observations report
  56. The EP-WXT trigger 01709251266 is likely a flaring star
  57. EP260110a: SVOM/C-GFT upper limit
  58. GRB 260104A: Swift-BAT refined analysis
  59. GRB 260101A: Swift-BAT refined analysis
  60. Fermi GRB 260107A: Global MASTER-Net observations report
  61. GRB 260107A: Fermi GBM Final Real-time Localization
  62. Fermi GRB 260105A: Global MASTER-Net observations report
  63. EP260105a: Global MASTER-Net observations report
  64. GRB 260104C: Fermi GBM Final Real-time Localization
  65. Fermi GRB 260104B: Global MASTER-Net observations report
  66. SVOM GRB260103.08: Global MASTER-Net observations report
  67. EP260101a: Global MASTER-Net observations report
  68. GRB 260101A: Swift detection of a burst with an optical counterpart
  69. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  70. Fermi GRB 251228A: Global MASTER-Net observations report
  71. SVOM GRB251227.07: Global MASTER-Net observations report
  72. IceCube Alert 251225.84: Global MASTER-Net observations report
  73. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  74. IceCube Alert 251218.85: Global MASTER-Net observations report
  75. Fermi GRB 251217A: Global MASTER-Net observations report
  76. Fermi GRB 251215A: Global MASTER-Net observations report
  77. GRB 251214B: UAFO optical upper limit
  78. GRB 251202A: radio detection with the VLA
  79. EP251214b: Global MASTER-Net observations report
  80. GRB 251214B: LCO detection of the optical counterpart
  81. EP251214a: Global MASTER-Net observations report
  82. IceCube-251210A: Upper limits from a search for additional neutrino events in IceCube
  83. GRB 251209A: Fermi GBM observation
  84. Fermi GRB 251208C: Global MASTER-Net observations report
  85. GRB 251208B: GROWTH-India Telescope optical upper limits
  86. GRB 251208A: Fermi GBM Final Real-time Localization
  87. GRB 251205A: Liverpool Telescope further optical follow-up observations
  88. GRB 251205A: Zeiss-1000 Koshka observatory optical observations
  89. GRB 251205A: Swift detection of a burst with an optical afterglow
  90. GRB 251126B: Fermi GBM Final Localization
  91. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  92. EP251129a/GRB 251129A: NOWT Detection
  93. Swift GRB 251201B : MASTER optical counterpart detection
  94. Swift GRB 251201B: Global MASTER-Net observations report
  95. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  96. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  97. GRB 251129A: Correction to the position of the optical counterpar
  98. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  99. SVOM GRB251129A: Global MASTER-Net observations report
  100. GRB 251126A: Swift-BAT refined analysis

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