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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"

4253 results found.

  1. Fermi GRB 260428A: Global MASTER-Net observations report
  2. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  3. Fermi GRB 260421C: Global MASTER-Net observations report
  4. Fermi GRB 260421B: Global MASTER-Net observations report
  5. GRB 260421B: LCO optical afterglow confirmation
  6. Fermi GRB 260417B: Global MASTER-Net observations report
  7. EP260417a: Global MASTER-Net observations report
  8. EP260416a: GMG Optical Observation
  9. Fermi GRB 260417A: Global MASTER-Net observations report
  10. GRB 260417A: AstroSat CZTI detection
  11. IPN triangulation of GRB 260411B
  12. EP260416a: Einstein Probe detection of an X-ray transient
  13. Fermi trigger No 797912738: Global MASTER-Net observations report
  14. EP260321a: CMO SAI J,K observations
  15. Fermi GRB 260412A: Global MASTER-Net observations report
  16. GRB260411B: 3.6m DOT optical observation
  17. Fermi trigger No 797039833: Global MASTER-Net observations report
  18. EP260403a: COLIBRÍ optical counterpart candidate
  19. EP260403a: Einstein Probe detection of an X-ray transient
  20. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  21. Fermi GRB 260401A: Global MASTER-Net observations report
  22. EP260329b: Mondy and Assy-Turgen optical upper limits
  23. EP260329b: GOTO detection of optical counterpart
  24. EP260329a: COLIBRÍ optical upper limit
  25. EP260329b: Global MASTER-Net observations report
  26. Fermi trigger No 796485221: Global MASTER-Net observations report
  27. EP 260329b: COLIBRÍ optical observations
  28. EP260329b: LCO optical observations of the counterpart
  29. EP-WXT trigger 01709259209: TRT optical counterpart detection
  30. EP260321A: Mondy optical observations
  31. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  32. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  33. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  34. GRB 260310A / AT 2026fgk: radio detection with the VLA
  35. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  36. EP260314a: SVOM/VT optical candidate
  37. Fermi trigger No 795185313: Global MASTER-Net observations report
  38. IceCube Alert 260315A: Global MASTER-Net observations report
  39. Fermi GRB 260313A: Global MASTER-Net observations report
  40. GRB 260312B: AstroSat CZTI detection
  41. GRB 260307B: Mephisto optical upper limits
  42. GRB 260307B: possible NOT optical counterpart
  43. EP260302a: SVOM/VT optical observation
  44. EP260306a: Einstein Probe detection of an X-ray transient
  45. GRB 260303A: 1.3m DFOT optical upper limit
  46. GRB 260303B: AstroSat CZTI detection
  47. GRB 260304A: AstroSat CZTI detection of a long burst
  48. EP260227a: Global MASTER-Net observations report
  49. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  50. LAT GRB260226.44: Global MASTER-Net observations report
  51. EP260214a: VLA 6 GHz detection
  52. GRB 260223A: DDOTI Optical Candidate
  53. Fermi GRB 260223A: Global MASTER-Net observations report
  54. EP260221a: Global MASTER-Net observations report
  55. Fermi trigger No 792537871: Global MASTER-Net observations report
  56. Fermi GRB 260210C: Global MASTER-Net observations report
  57. EP260210a: Global MASTER-Net observations report
  58. IPN triangulation of GRB 260207B (short/hard with EE)
  59. Fermi GRB 260209A: Global MASTER-Net observations report
  60. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  61. Fermi GRB 260208A: Global MASTER-Net observations report
  62. GRB 251230A: MeerLICHT afterglow detection
  63. GRB 260130A: Insight-HXMT/HE detection
  64. GRB 260130A: GECAM-B observation of a short burst
  65. GRB 260131B: MAXI/GSC detection
  66. GRB 260130A: Fermi GBM Detection
  67. GRB 260130A: Fermi GBM Final Real-time Localization
  68. Fermi GRB 260129A: Global MASTER-Net observations report
  69. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  70. GRB 260129B: Fermi GBM Final Localization
  71. GRB 260129A: Fermi GBM Final Localization
  72. EP260128a: NOT optical counterpart candidate
  73. EP260128a: LCO optical upper limits
  74. EP260126a: SVOM/VT optical upperlimit
  75. EP260128a: Global MASTER-Net observations report
  76. GRB 251222A: SVOM/ECLAIRs refined analysis
  77. GRB 260125A: GOTO candidate optical counterpart
  78. GRB 260120B: SVOM/C-GFT optical counterpart detection
  79. SVOM GRB260119.90: Global MASTER-Net observations report
  80. EP260119a: Global MASTER-Net observations report
  81. EP260119a: COLIBRÍ optical counterpart candidate
  82. SVOM GRB260117.82: Global MASTER-Net observations report
  83. Swift trigger on the HMXB 1A 1118-61
  84. EP 260116a: COLIBRÍ optical upper limit
  85. GRB 260114A: Fermi GBM observation
  86. Swift Trigger 1439093: is probably not GRB 260113A
  87. GRB 260111A: GOTO optical upper limits
  88. EP260110a: SVOM/VT optical upper limits
  89. GRB 260109C: LCO optical upper limits
  90. FRB 20251229A: COLIBRÍ optical upper limits
  91. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  92. Fermi GRB 260104B: Global MASTER-Net observations report
  93. Swift GRB 260104A: Global MASTER-Net observations report
  94. EP251229a: BOOTES-2 early optical upper limit
  95. EP251229a: NOT optical upper limits
  96. EP251229a: Global MASTER-Net observations report
  97. Fermi GRB 251228A: Global MASTER-Net observations report
  98. SVOM GRB251227.07: Global MASTER-Net observations report
  99. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  100. EP251222b/GRB 251222A: SVOM/GRM observation

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