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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

39320 results found.

  1. Fermi GRB 260127A: Global MASTER-Net observations report
  2. GRB 260127A: Fermi GBM Observation
  3. GRB 260127A: COLIBRÍ optical observations
  4. GRB 260127A: NOT optical observations
  5. GRB 260127B: Swift ToO observations
  6. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  7. GRB 260127A: Swift-XRT refined Analysis
  8. GRB 260127B: GOTO candidate optical counterpart
  9. GRB 260127A: SVOM/C-GFT optical observations
  10. GRB 260127A: Enhanced Swift-XRT position
  11. Fermi GRB 260127B: Global MASTER-Net observations report
  12. GRB 260127B: Fermi GBM Final Real-time Localization
  13. GRB 260127A: Prompt enhanced Swift-XRT position
  14. Swift GRB 260127A: Global MASTER-Net observations report
  15. GRB 260127A: LCO optical afterglow discovery
  16. GRB 260127A: Swift detection of a burst
  17. GRB 260127A: Fermi GBM Final Real-time Localization
  18. GRB 260125A: Swift-XRT observations
  19. EP260126a: COLIBRÍ optical upper limits
  20. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  21. Konus-Wind detection of GRB 260120B
  22. GRB 251222A: SVOM/ECLAIRs refined analysis
  23. GRB 260125A: Swift ToO observations
  24. GRB 260125A: GOTO candidate optical counterpart
  25. Fermi GRB 260125B: Global MASTER-Net observations report
  26. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  27. GRB 260125B: Fermi GBM Final Real-time Localization
  28. GRB 260125A: Fermi GBM Final Real-time Localization
  29. GRB 260114A: SVOM/VT optical upper limits
  30. GRB 260120A: AstroSat CZTI detection
  31. GRB 260122B: Swift-BAT refined analysis
  32. GRB 260120B: SVOM/GRM observation
  33. GRB 260120A: GECAM-B observation
  34. GRB 260120B: AstroSat CZTI detection
  35. GRB 260114A: Insight-HXMT/HE detection
  36. GRB 260122B: Swift detection of a burst
  37. Swift GRB260122.97: Global MASTER-Net observations report
  38. EP260119a: Assy AZT-20 optical observations
  39. EP260119a: Mondy and SAO RAS optical upper limits
  40. GRB 260122A: Fermi GBM Final Real-time Localization
  41. Fermi GRB 260120C: Global MASTER-Net observations report
  42. GRB 260120B: Swift-BAT refined analysis
  43. GRB 260120B: Swift-XRT refined Analysis
  44. EP260116a: COLIBRÍ further observations
  45. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  46. GRB 260120B: Fermi GBM Observation
  47. GRB 260120B: Swift/UVOT Detection
  48. GRB 260120B: COLIBRÍ optical upper limits
  49. SVOM GRB260121.06: Global MASTER-Net observations report
  50. GRB 260120B: Enhanced Swift-XRT position
  51. GRB 260120B: SVOM/C-GFT optical counterpart detection
  52. GRB 260120C: Fermi GBM Final Real-time Localization
  53. GRB 260101A: 239Alferov CubeSat detection
  54. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  55. GRB 260120B: Swift detection of a burst
  56. Swift GRB260120B: Global MASTER-Net observations report
  57. GRB 260120B: Fermi GBM Final Real-time Localization
  58. EP260119A: Mondy I-Band Observations
  59. Fermi trigger No 790601190: Global MASTER-Net observations report
  60. Fermi trigger No 790570272: Global MASTER-Net observations report
  61. GRB 260114A: Swift/UVOT Upper Limits
  62. GRB 251202A: further radio observations with the VLA
  63. EP260119a: KAIT optical observations
  64. GRB 260120A: Fermi GBM Final Real-time Localization
  65. EP260119a: SAO RAS optical observations
  66. SVOM GRB260119.92: Global MASTER-Net observations report
  67. SVOM GRB260119.92: Global MASTER-Net observations report
  68. SVOM GRB260119.90: Global MASTER-Net observations report
  69. EP260116a: COLIBRÍ detection of a fading optical source
  70. GRB 251208D: SVOM/ECLAIRs refined analysis
  71. GRB 251208D: SVOM/ECLAIRs refined analysis
  72. GRB 260117A: Swift-XRT afterglow detection
  73. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  74. EP260119a: Global MASTER-Net observations report
  75. GRB 260115A: AstroSat CZTI detection
  76. EP260119a: LCO optical observations
  77. GRB 260117A: ZTSh optical upper limit
  78. EP260119a: COLIBRÍ optical counterpart candidate
  79. GRB 260110A: SVOM detection of a burst through offline search
  80. Swift GRB260118.48: Global MASTER-Net observations report
  81. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  82. SVOM GRB260117.82: Global MASTER-Net observations report
  83. Swift trigger on the HMXB 1A 1118-61
  84. GRB 260117A: SVOM/VT optical candidate
  85. GRB 260117A: SVOM/C-GFT upper limit
  86. GRB 260117A: Swift-XRT observations
  87. GRB 260117A: Swift ToO observations
  88. GRB 260117A: SVOM detection of a long faint burst
  89. EP 260116a: COLIBRÍ optical upper limit
  90. Swift triggered on the HMXB 1A 1118-61
  91. GRB 260115A: GECAM-B observation
  92. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  93. EP260116A: 1.3m DFOT optical upper limit
  94. GRB 260114A: VLT/MUSE spectroscopic observations
  95. EP260116a: Global MASTER-Net observations report
  96. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  97. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  98. IceCube Alert 260115.73: Global MASTER-Net observations report
  99. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  100. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)

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