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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"

11102 results found.

  1. GRB 260208A: Glowbug gamma-ray detection
  2. GRB 260208A: NuSTAR detection of prompt emission
  3. GRB 260208A: Fermi GBM Observation
  4. Fermi GRB 260209A: Global MASTER-Net observations report
  5. GRB 260208B: Swift-XRT observations
  6. GRB 260131A/B: continued Mondy optical observations
  7. GRB 260208B: COLIBRÍ optical observations
  8. GRB 260208A: Mondy optical observations
  9. GRB 260208A: 1.3m DFOT optical detection
  10. GRB 260208A: COLIBRÍ optical observations
  11. GRB 260208B: EP-FXT observation
  12. GRB 260208A: NOT spectroscopic redshift z = 2.36
  13. GRB 260208A: Liverpool Telescope optical detection
  14. Fermi GRB 260208C: Global MASTER-Net observations report
  15. GRB 260208B: SVOM/VT optical candidate
  16. GRB 260208A: GECAM-B observation of a bright burst
  17. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  18. GRB 260209A: Fermi GBM Final Real-time Localization
  19. GRB 260208A: SVOM/VT optical observation
  20. Fermi GRB 260208D: Global MASTER-Net observations report
  21. GRB 260208D: Fermi GBM Final Real-time Localization
  22. GRB 260208A: Swift-XRT observations
  23. GRB 260208B: Swift ToO observations
  24. GRB 260208B: SVOM/GRM observation of a bright burst
  25. GRB 260208B: Fermi GBM Detection
  26. GRB 260208B: Fermi-LAT detection
  27. GRB 260208C: Fermi GBM Final Real-time Localization
  28. GRB 260208A: Fermi-LAT detection
  29. GRB 260207B: GECAM-B observation
  30. GRB 260208A: Swift ToO observations
  31. GRB 260208A: Fermi GBM Classification Correction
  32. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  33. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  34. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  35. GRB 260208B: Fermi GBM Final Real-time Localization
  36. Fermi GRB 260208A: Global MASTER-Net observations report
  37. Fermi Gamma-ray Burst Monitor trigger 792220053/260208214 is not a GRB
  38. GRB 260208A: Fermi GBM Final Real-time Localization
  39. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  40. GRB 260207A : MASTER optical counterpart discovery
  41. GRB 260131A/B: Mondy and Terskol optical observations
  42. Fermi GRB 260207B: Global MASTER-Net observations report
  43. GRB 260207B: Fermi GBM Final Real-time Localization
  44. GRB 260207A: Fermi GBM Final Localization
  45. Fermi trigger No 792135758: Global MASTER-Net observations report
  46. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  47. GRB 260204A : MASTER Global robotic net optical observations
  48. Fermi GBM Sub-Threshold Detection of GRB 260204A
  49. GRB 260204B: Fermi GBM Final Real-time Localization
  50. GRB 260131A/B: OHP/T193 optical observations
  51. GRB 260131A: KAIT optical observations
  52. GRB 260131A: FTW optical and NIR observations
  53. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  54. GRID detection of GRB 260131A/B
  55. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  56. GRB 260130A: Insight-HXMT/HE detection
  57. GRB 260130A: GECAM-B observation of a short burst
  58. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  59. GRB 260131A/B: EP/FXT X-ray afterglow detection
  60. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  61. GRB 260127B: Insight-HXMT/HE detection
  62. GRB 260127B: GECAM-B observation of a short burst
  63. GRB 260127A: GECAM-B observation
  64. GRB 260131A: NOT spectroscopic redshift z = 1.434
  65. Konus-Wind detection of GRB 260128A / EP260128a
  66. GRB 260131A: Insight-HXMT/HE detection
  67. Konus-Wind detection of GRB 260131A/B
  68. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  69. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  70. GRB 260131A/B: Fermi GBM Observation
  71. GRB 260131A: Fermi GBM Final Real-time Localization
  72. GRB 260127B: AstroSat CZTI detection
  73. GRB 260130A: Fermi GBM Detection
  74. GRB 260127B: Fermi GBM Detection
  75. Fermi GRB 260130A: Global MASTER-Net observations report
  76. GRB 260130A: Fermi GBM Final Real-time Localization
  77. Fermi GRB 260129A: Global MASTER-Net observations report
  78. IPN triangulation of GRB 260121A
  79. GRB 260129B: Fermi GBM Final Localization
  80. GRB 260129A: Fermi GBM Final Localization
  81. IPN triangulation of GRB 260127B (short)
  82. GRB 260127B: Swift-XRT observations
  83. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  84. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  85. Fermi GRB 260127A: Global MASTER-Net observations report
  86. GRB 260127A: Fermi GBM Observation
  87. GRB 260127A: COLIBRÍ optical observations
  88. GRB 260127A: NOT optical observations
  89. GRB 260127B: Swift ToO observations
  90. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  91. GRB 260127B: GOTO candidate optical counterpart
  92. GRB 260127A: SVOM/C-GFT optical observations
  93. Fermi GRB 260127B: Global MASTER-Net observations report
  94. GRB 260127B: Fermi GBM Final Real-time Localization
  95. GRB 260127A: LCO optical afterglow discovery
  96. GRB 260127A: Fermi GBM Final Real-time Localization
  97. GRB 260125A: Swift-XRT observations
  98. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  99. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  100. Konus-Wind detection of GRB 260120B

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