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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"
  1. GRB 260209A: Fermi GBM Final Real-time Localization
  2. GRB 260208A: SVOM/VT optical observation
  3. Fermi GRB 260208D: Global MASTER-Net observations report
  4. GRB 260208D: Fermi GBM Final Real-time Localization
  5. GRB 260208A: Swift-XRT observations
  6. GRB 260208B: Swift ToO observations
  7. GRB 260208B: SVOM/GRM observation of a bright burst
  8. GRB 260208B: Fermi GBM Detection
  9. LAT GRB 260208B: Global MASTER-Net observations report
  10. GRB 260208B: Fermi-LAT detection
  11. GRB 260208C: Fermi GBM Final Real-time Localization
  12. GRB 260208A: Fermi-LAT detection
  13. GRB 260207B: GECAM-B observation
  14. GRB 260208A: Swift ToO observations
  15. GRB 260208A: Fermi GBM Classification Correction
  16. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  17. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  18. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  19. GRB 260208B: Fermi GBM Final Real-time Localization
  20. Fermi GRB 260208A: Global MASTER-Net observations report
  21. Fermi Gamma-ray Burst Monitor trigger 792220053/260208214 is not a GRB
  22. GRB 260208A: Fermi GBM Final Real-time Localization
  23. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  24. GRB 260207A : MASTER optical counterpart discovery
  25. GRB 260131A/B: Mondy and Terskol optical observations
  26. Fermi GRB 260207B: Global MASTER-Net observations report
  27. GRB 260206A: Swift-XRT observations
  28. GRB 260207B: Fermi GBM Final Real-time Localization
  29. GRB 260207A: Fermi GBM Final Localization
  30. Fermi trigger No 792135758: Global MASTER-Net observations report
  31. EP260131a: VLA detection
  32. GRB 260206A: Tiled Swift observations
  33. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  34. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  35. GRB 260204A: Swift-XRT observations
  36. GRB 260204A: LCO optical afterglow detection
  37. GRB 260204A: SVOM/VT optical candidate
  38. GRB 260204A : MASTER Global robotic net optical observations
  39. Fermi GBM Sub-Threshold Detection of GRB 260204A
  40. GRB 260204A: GOTO optical upper limit
  41. GRB 260204A: LCO optical upper limits
  42. EP260110a: Late GTC/EMIR near-infrared observations
  43. GRB 260204B: Fermi GBM Final Real-time Localization
  44. GRB 260204A: SVOM detection of a burst
  45. GRB 260121A: 239Alferov CubeSat detection
  46. Konus-Wind detection of GRB 260121A
  47. GRB 260131A/B: OHP/T193 optical observations
  48. GRB 260131A: KAIT optical observations
  49. GRB 251230A: MeerLICHT afterglow detection
  50. GRB 260131A: FTW optical and NIR observations
  51. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  52. GRID detection of GRB 260131A/B
  53. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  54. GRB 260130A: Insight-HXMT/HE detection
  55. GRB 260130A: GECAM-B observation of a short burst
  56. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  57. GRB 260131A/B: EP/FXT X-ray afterglow detection
  58. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  59. GRB 260127B: Insight-HXMT/HE detection
  60. GRB 260127B: GECAM-B observation of a short burst
  61. GRB 260127A: GECAM-B observation
  62. GRB 260131A: NOT spectroscopic redshift z = 1.434
  63. EP260131a: Liverpool Telescope optical upper limits
  64. EP260131a: COLIBRÍ further observations
  65. Konus-Wind detection of GRB 260128A / EP260128a
  66. GRB 260131A: Insight-HXMT/HE detection
  67. Konus-Wind detection of GRB 260131A/B
  68. EP260131a: SVOM/VT optical observation
  69. EP260131a: Xinglong optical upper limit
  70. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  71. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  72. GRB 260131A/B: Fermi GBM Observation
  73. EP260131a: COLIBRÍ observations of slow optical fading
  74. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  75. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  76. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  77. GRB 260131B: MAXI/GSC detection
  78. GRB 260131A: Fermi GBM Final Real-time Localization
  79. EP260131a: COLIBRÍ optical observations of the counterpart
  80. EP260131a: Las Cumbres detection of an optical counterpart
  81. GRB 260127B: AstroSat CZTI detection
  82. GRB 260130A: Fermi GBM Detection
  83. EP260131a: Einstein Probe detection of an X-ray transient
  84. GRB 260127B: Fermi GBM Detection
  85. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  86. Fermi GRB 260130A: Global MASTER-Net observations report
  87. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  88. GRB 260130A: Fermi GBM Final Real-time Localization
  89. Fermi GRB 260129A: Global MASTER-Net observations report
  90. GRB 260128B: LCO optical upper limits
  91. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  92. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  93. IPN triangulation of GRB 260121A
  94. GRB 260127A: Swift-BAT refined analysis
  95. GRB 260129B: Fermi GBM Final Localization
  96. GRB 260128B: SVOM detection of a burst through offline search
  97. GRB 260129A: Fermi GBM Final Localization
  98. IPN triangulation of GRB 260127B (short)
  99. GRB 260127B: Swift-XRT observations
  100. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations

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