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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. Konus-Wind detection of GRB 260127B
  2. EP260209a: COLIBRÍ optical upper limit
  3. Fermi GRB 260210C: Global MASTER-Net observations report
  4. EP260209a: LCO optical upper limits
  5. EP260210a: Global MASTER-Net observations report
  6. EP260210a: refined analysis of the EP-FXT observation
  7. EP260209a: Global MASTER-Net observations report
  8. GRB 260208A: LCO detection of the optical counterpart
  9. EP260209a: Einstein Probe detection of a fast X-ray transient
  10. EP260210a: Optical upper limits with Kinder observations
  11. IPN triangulation of GRB 260207B (short/hard with EE)
  12. GRB 260210C: Fermi GBM Final Real-time Localization
  13. GRB 260210A: Glowbug gamma-ray detection
  14. GRB 260210B: Fermi GBM Final Real-time Localization
  15. EP260210a: SVOM/VT optical upper limit
  16. GRB 260210A: AstroSat CZTI detection
  17. GRB 260208C: AstroSat CZTI detection
  18. EP260210a: COLIBRÍ optical upper limit
  19. EP260210a: SVOM/C-GFT upper limit
  20. GRB 260208B: refined analysis of the EP-FXT observation
  21. EP260210a: Einstein Probe detection of an X-ray transient
  22. GRB 260207B: AstroSat CZTI detection
  23. GRB 260208C: SVOM/GRM observation
  24. GRB 260204A: Swift-XRT afterglow detection
  25. GRB 260208B: AstroSat CZTI detection of a bright long burst
  26. GRB260208A: Liverpool Telescope optical follow-up observations
  27. GRB 260208A: Glowbug gamma-ray detection
  28. GRB 260208A: NuSTAR detection of prompt emission
  29. GRB 260208A: Fermi GBM Observation
  30. Fermi GRB 260209A: Global MASTER-Net observations report
  31. GRB 260208B: Swift-XRT observations
  32. GRB 260131A/B: continued Mondy optical observations
  33. GRB 260204A: Swift/UVOT Upper Limits
  34. GRB 260208B: COLIBRÍ optical observations
  35. GRB 260208A: Mondy optical observations (duplicate submission)
  36. GRB 260208A: Mondy optical observations
  37. GRB 260208A: 1.3m DFOT optical detection
  38. GRB 260208A: COLIBRÍ optical observations
  39. GRB 260208B: EP-FXT observation
  40. GRB 260208A: NOT spectroscopic redshift z = 2.36
  41. GRB 260208A: Liverpool Telescope optical detection
  42. Fermi GRB 260208C: Global MASTER-Net observations report
  43. GRB 260208B: SVOM/VT optical candidate
  44. GRB 260208A: GECAM-B observation of a bright burst
  45. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  46. GRB 260209A: Fermi GBM Final Real-time Localization
  47. GRB 260208A: SVOM/VT optical observation
  48. Fermi GRB 260208D: Global MASTER-Net observations report
  49. GRB 260208D: Fermi GBM Final Real-time Localization
  50. GRB 260208A: Swift-XRT observations
  51. GRB 260208B: Swift ToO observations
  52. GRB 260208B: SVOM/GRM observation of a bright burst
  53. GRB 260208B: Fermi GBM Detection
  54. LAT GRB 260208B: Global MASTER-Net observations report
  55. GRB 260208B: Fermi-LAT detection
  56. GRB 260208C: Fermi GBM Final Real-time Localization
  57. GRB 260208A: Fermi-LAT detection
  58. GRB 260207B: GECAM-B observation
  59. GRB 260208A: Swift ToO observations
  60. GRB 260208A: Fermi GBM Classification Correction
  61. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  62. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  63. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  64. GRB 260208B: Fermi GBM Final Real-time Localization
  65. Fermi GRB 260208A: Global MASTER-Net observations report
  66. Fermi Gamma-ray Burst Monitor trigger 792220053/260208214 is not a GRB
  67. GRB 260208A: Fermi GBM Final Real-time Localization
  68. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  69. GRB 260207A : MASTER optical counterpart discovery
  70. GRB 260131A/B: Mondy and Terskol optical observations
  71. Fermi GRB 260207B: Global MASTER-Net observations report
  72. GRB 260206A: Swift-XRT observations
  73. GRB 260207B: Fermi GBM Final Real-time Localization
  74. GRB 260207A: Fermi GBM Final Localization
  75. Fermi trigger No 792135758: Global MASTER-Net observations report
  76. EP260131a: VLA detection
  77. GRB 260206A: Tiled Swift observations
  78. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  79. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  80. GRB 260204A: Swift-XRT observations
  81. GRB 260204A: LCO optical afterglow detection
  82. GRB 260204A: SVOM/VT optical candidate
  83. GRB 260204A : MASTER Global robotic net optical observations
  84. Fermi GBM Sub-Threshold Detection of GRB 260204A
  85. GRB 260204A: GOTO optical upper limit
  86. GRB 260204A: LCO optical upper limits
  87. EP260110a: Late GTC/EMIR near-infrared observations
  88. GRB 260204B: Fermi GBM Final Real-time Localization
  89. GRB 260204A: SVOM detection of a burst
  90. GRB 260121A: 239Alferov CubeSat detection
  91. Konus-Wind detection of GRB 260121A
  92. GRB 260131A/B: OHP/T193 optical observations
  93. GRB 260131A: KAIT optical observations
  94. GRB 251230A: MeerLICHT afterglow detection
  95. GRB 260131A: FTW optical and NIR observations
  96. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  97. GRID detection of GRB 260131A/B
  98. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  99. GRB 260130A: Insight-HXMT/HE detection
  100. GRB 260130A: GECAM-B observation of a short burst

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