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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"

4252 results found.

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

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