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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"

36012 results found.

  1. GRB 260208C: Fermi GBM Final Real-time Localization
  2. GRB 260208A: Fermi-LAT detection
  3. GRB 260207B: GECAM-B observation
  4. GRB 260208A: Swift ToO observations
  5. GRB 260208A: Fermi GBM Classification Correction
  6. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  7. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  8. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  9. GRB 260208B: Fermi GBM Final Real-time Localization
  10. Fermi GRB 260208A: Global MASTER-Net observations report
  11. Fermi Gamma-ray Burst Monitor trigger 792220053/260208214 is not a GRB
  12. GRB 260208A: Fermi GBM Final Real-time Localization
  13. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  14. GRB 260207A : MASTER optical counterpart discovery
  15. GRB 260131A/B: Mondy and Terskol optical observations
  16. Fermi GRB 260207B: Global MASTER-Net observations report
  17. GRB 260206A: Swift-XRT observations
  18. GRB 260207B: Fermi GBM Final Real-time Localization
  19. GRB 260207A: Fermi GBM Final Localization
  20. EP260131a: VLA detection
  21. GRB 260206A: Tiled Swift observations
  22. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  23. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  24. GRB 260204A: Swift-XRT observations
  25. GRB 260204A: LCO optical afterglow detection
  26. GRB 260204A: SVOM/VT optical candidate
  27. GRB 260204A : MASTER Global robotic net optical observations
  28. Fermi GBM Sub-Threshold Detection of GRB 260204A
  29. GRB 260204A: GOTO optical upper limit
  30. GRB 260204A: LCO optical upper limits
  31. GRB 260204B: Fermi GBM Final Real-time Localization
  32. GRB 260204A: SVOM detection of a burst
  33. GRB 260121A: 239Alferov CubeSat detection
  34. Konus-Wind detection of GRB 260121A
  35. GRB 260131A/B: OHP/T193 optical observations
  36. GRB 260131A: KAIT optical observations
  37. GRB 251230A: MeerLICHT afterglow detection
  38. GRB 260131A: FTW optical and NIR observations
  39. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  40. GRID detection of GRB 260131A/B
  41. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  42. GRB 260130A: Insight-HXMT/HE detection
  43. GRB 260130A: GECAM-B observation of a short burst
  44. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  45. GRB 260131A/B: EP/FXT X-ray afterglow detection
  46. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  47. GRB 260127B: Insight-HXMT/HE detection
  48. GRB 260127B: GECAM-B observation of a short burst
  49. GRB 260127A: GECAM-B observation
  50. GRB 260131A: NOT spectroscopic redshift z = 1.434
  51. Konus-Wind detection of GRB 260128A / EP260128a
  52. GRB 260131A: Insight-HXMT/HE detection
  53. Konus-Wind detection of GRB 260131A/B
  54. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  55. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  56. GRB 260131A/B: Fermi GBM Observation
  57. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  58. GRB 260131B: MAXI/GSC detection
  59. GRB 260131A: Fermi GBM Final Real-time Localization
  60. GRB 260127B: AstroSat CZTI detection
  61. GRB 260130A: Fermi GBM Detection
  62. GRB 260127B: Fermi GBM Detection
  63. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  64. Fermi GRB 260130A: Global MASTER-Net observations report
  65. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  66. GRB 260130A: Fermi GBM Final Real-time Localization
  67. Fermi GRB 260129A: Global MASTER-Net observations report
  68. GRB 260128B: LCO optical upper limits
  69. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  70. IPN triangulation of GRB 260121A
  71. GRB 260127A: Swift-BAT refined analysis
  72. GRB 260129B: Fermi GBM Final Localization
  73. GRB 260128B: SVOM detection of a burst through offline search
  74. GRB 260129A: Fermi GBM Final Localization
  75. IPN triangulation of GRB 260127B (short)
  76. GRB 260127B: Swift-XRT observations
  77. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  78. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  79. Fermi GRB 260127A: Global MASTER-Net observations report
  80. GRB 260127A: Fermi GBM Observation
  81. GRB 260127A: COLIBRÍ optical observations
  82. GRB 260127A: NOT optical observations
  83. GRB 260127B: Swift ToO observations
  84. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  85. GRB 260127A: Swift-XRT refined Analysis
  86. GRB 260127B: GOTO candidate optical counterpart
  87. GRB 260127A: SVOM/C-GFT optical observations
  88. GRB 260127A: Enhanced Swift-XRT position
  89. Fermi GRB 260127B: Global MASTER-Net observations report
  90. GRB 260127B: Fermi GBM Final Real-time Localization
  91. GRB 260127A: Prompt enhanced Swift-XRT position
  92. Swift GRB 260127A: Global MASTER-Net observations report
  93. GRB 260127A: LCO optical afterglow discovery
  94. GRB 260127A: Swift detection of a burst
  95. GRB 260127A: Fermi GBM Final Real-time Localization
  96. GRB 260125A: Swift-XRT observations
  97. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  98. Konus-Wind detection of GRB 260120B
  99. GRB 251222A: SVOM/ECLAIRs refined analysis
  100. GRB 260125A: Swift ToO observations

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