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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"

11114 results found.

  1. Konus-Wind detection of GRB 260127B
  2. Fermi GRB 260210C: Global MASTER-Net observations report
  3. GRB 260208A: LCO detection of the optical counterpart
  4. IPN triangulation of GRB 260207B (short/hard with EE)
  5. GRB 260210C: Fermi GBM Final Real-time Localization
  6. GRB 260210B: Fermi GBM Final Real-time Localization
  7. GRB 260208C: AstroSat CZTI detection
  8. GRB 260208B: refined analysis of the EP-FXT observation
  9. GRB 260207B: AstroSat CZTI detection
  10. GRB 260208C: SVOM/GRM observation
  11. GRB 260208B: AstroSat CZTI detection of a bright long burst
  12. GRB260208A: Liverpool Telescope optical follow-up observations
  13. GRB 260208A: Glowbug gamma-ray detection
  14. GRB 260208A: NuSTAR detection of prompt emission
  15. GRB 260208A: Fermi GBM Observation
  16. Fermi GRB 260209A: Global MASTER-Net observations report
  17. GRB 260208B: Swift-XRT observations
  18. GRB 260131A/B: continued Mondy optical observations
  19. GRB 260208B: COLIBRÍ optical observations
  20. GRB 260208A: Mondy optical observations
  21. GRB 260208A: 1.3m DFOT optical detection
  22. GRB 260208A: COLIBRÍ optical observations
  23. GRB 260208B: EP-FXT observation
  24. GRB 260208A: NOT spectroscopic redshift z = 2.36
  25. GRB 260208A: Liverpool Telescope optical detection
  26. Fermi GRB 260208C: Global MASTER-Net observations report
  27. GRB 260208B: SVOM/VT optical candidate
  28. GRB 260208A: GECAM-B observation of a bright burst
  29. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  30. GRB 260209A: Fermi GBM Final Real-time Localization
  31. GRB 260208A: SVOM/VT optical observation
  32. Fermi GRB 260208D: Global MASTER-Net observations report
  33. GRB 260208D: Fermi GBM Final Real-time Localization
  34. GRB 260208A: Swift-XRT observations
  35. GRB 260208B: Swift ToO observations
  36. GRB 260208B: SVOM/GRM observation of a bright burst
  37. GRB 260208B: Fermi GBM Detection
  38. GRB 260208B: Fermi-LAT detection
  39. GRB 260208C: Fermi GBM Final Real-time Localization
  40. GRB 260208A: Fermi-LAT detection
  41. GRB 260207B: GECAM-B observation
  42. GRB 260208A: Swift ToO observations
  43. GRB 260208A: Fermi GBM Classification Correction
  44. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  45. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  46. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  47. GRB 260208B: Fermi GBM Final Real-time Localization
  48. Fermi GRB 260208A: Global MASTER-Net observations report
  49. Fermi Gamma-ray Burst Monitor trigger 792220053/260208214 is not a GRB
  50. GRB 260208A: Fermi GBM Final Real-time Localization
  51. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  52. GRB 260207A : MASTER optical counterpart discovery
  53. GRB 260131A/B: Mondy and Terskol optical observations
  54. Fermi GRB 260207B: Global MASTER-Net observations report
  55. GRB 260207B: Fermi GBM Final Real-time Localization
  56. GRB 260207A: Fermi GBM Final Localization
  57. Fermi trigger No 792135758: Global MASTER-Net observations report
  58. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  59. GRB 260204A : MASTER Global robotic net optical observations
  60. Fermi GBM Sub-Threshold Detection of GRB 260204A
  61. GRB 260204B: Fermi GBM Final Real-time Localization
  62. GRB 260131A/B: OHP/T193 optical observations
  63. GRB 260131A: KAIT optical observations
  64. GRB 260131A: FTW optical and NIR observations
  65. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  66. GRID detection of GRB 260131A/B
  67. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  68. GRB 260130A: Insight-HXMT/HE detection
  69. GRB 260130A: GECAM-B observation of a short burst
  70. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  71. GRB 260131A/B: EP/FXT X-ray afterglow detection
  72. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  73. GRB 260127B: Insight-HXMT/HE detection
  74. GRB 260127B: GECAM-B observation of a short burst
  75. GRB 260127A: GECAM-B observation
  76. GRB 260131A: NOT spectroscopic redshift z = 1.434
  77. Konus-Wind detection of GRB 260128A / EP260128a
  78. GRB 260131A: Insight-HXMT/HE detection
  79. Konus-Wind detection of GRB 260131A/B
  80. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  81. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  82. GRB 260131A/B: Fermi GBM Observation
  83. GRB 260131A: Fermi GBM Final Real-time Localization
  84. GRB 260127B: AstroSat CZTI detection
  85. GRB 260130A: Fermi GBM Detection
  86. GRB 260127B: Fermi GBM Detection
  87. Fermi GRB 260130A: Global MASTER-Net observations report
  88. GRB 260130A: Fermi GBM Final Real-time Localization
  89. Fermi GRB 260129A: Global MASTER-Net observations report
  90. IPN triangulation of GRB 260121A
  91. GRB 260129B: Fermi GBM Final Localization
  92. GRB 260129A: Fermi GBM Final Localization
  93. IPN triangulation of GRB 260127B (short)
  94. GRB 260127B: Swift-XRT observations
  95. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  96. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  97. Fermi GRB 260127A: Global MASTER-Net observations report
  98. GRB 260127A: Fermi GBM Observation
  99. GRB 260127A: COLIBRÍ optical observations
  100. GRB 260127A: NOT optical observations

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