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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"

3039 results found.

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

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