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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"

11556 results found.

  1. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  2. GRB 260407A: GECAM-A detection
  3. GRB 260407A: Insight-HXMT/HE detection
  4. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  5. GRB 260404A: Fermi GBM Final Localization
  6. GRB 260407A: Glowbug gamma-ray detection
  7. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  8. GRB 260310A / AT2026fgk: X-ray rebrightening
  9. GRID detection of GRB 260401A
  10. GRB 260407A: Fermi GBM Final Real-time Localization
  11. Fermi trigger No 797039833: Global MASTER-Net observations report
  12. GRB 260403A: GECAM-B observation of a long burst
  13. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  14. GRB 260330B: SVOM/VT further optical observation
  15. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  16. GRB 260330B: SVOM/ECLAIRs refined analysis
  17. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  18. GRB 260330B: SVOM/VT optical candidate
  19. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  20. GRB 260403A: AstroSat CZTI detection
  21. GRB 260402B: GECAM-B observation
  22. GRB 260403A: Fermi GBM Final Real-time Localization
  23. GRB 260402B: Fermi GBM Final Real-time Localization
  24. GRB 260401A: SVOM/GRM observation
  25. GRB 260401A: GECAM-B observation
  26. Fermi GRB 260401A: Global MASTER-Net observations report
  27. GRB 260401A: Fermi GBM Observation
  28. GRB 260401A: NuSTAR detection of prompt emission
  29. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  30. GRB 260401A: MAXI/GSC detection
  31. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  32. GRB 260401A: Fermi GBM Final Real-time Localization
  33. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  34. GRB 260330B: SVOM/VT optical upper limits
  35. Konus-Wind detection of GRB 260316B
  36. GRB 260321A: SVOM/ECLAIRs refined analysis
  37. GRB 260330A: Glowbug gamma-ray detection
  38. GRB 260310A: VLA Multi-frequency Radio Observations
  39. Fermi GBM Sub-Threshold Detection of GRB 260330B
  40. GRB 260330A: Fermi GBM Final Real-time Localization
  41. Fermi trigger No 796485221: Global MASTER-Net observations report
  42. GRB 260326A: Insight-HXMT/HE detection
  43. GRID detection of GRB 260326A
  44. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  45. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  46. GRB 260326A: Fermi GBM Detection
  47. GRB 260325A: Fermi GBM Final Localization
  48. GRB 260326A: Fermi GBM Final Real-time Localization
  49. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  50. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  51. IPN triangulation of GRB 260316B
  52. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  53. GRB 260310A: LBT optical observations
  54. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  55. Fermi GRB 260323A: Global MASTER-Net observations report
  56. GRB 260323A: Fermi GBM Final Real-time Localization
  57. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  58. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  59. GRB 260322A: Fermi GBM Final Localization
  60. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  61. GRB 260310A: continued optical observation at Mondy
  62. Fermi GBM Sub-Threshold Detection of GRB 260321A
  63. GRB 260318A: Glowbug gamma-ray detection
  64. GRB 260310A / AT 2026fgk: KAIT optical observations
  65. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  66. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  67. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  68. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  69. GRB 260310A/AT2026fgk: LBT near-infrared observations
  70. GRB 260318A: SVOM/GRM observation
  71. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  72. GRB 260318A: GECAM-B observation
  73. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  74. Fermi GRB 260318A: Global MASTER-Net observations report
  75. GRB 260318A: Fermi GBM Final Real-time Localization
  76. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  77. GRB 260310A / AT 2026fgk: radio detection with the VLA
  78. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  79. GRB 260310A / AT2026fgk: LCO optical observations
  80. GRB 260317A: Fermi GBM Final Localization
  81. GRB 260316B: GECAM-B observation
  82. GRB 260316B: SVOM/GRM observation
  83. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  84. EP260316a: COLIBRÍ faint optical counterpart candidate
  85. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  86. GRB 260316B: AstroSat CZTI detection
  87. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  88. GRB 260316B: Fermi GBM Final Real-time Localization
  89. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  90. GRB 260314A: Glowbug gamma-ray detection
  91. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  92. GRB 260310A / AT 2026fgk: iTelescope optical observations
  93. GRID detection of GRB 260312B
  94. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  95. Fermi trigger No 795185313: Global MASTER-Net observations report
  96. GRB 260314A: GECAM-B observation of a burst
  97. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  98. GRB 260310A / AT2026fgk: SAO RAS optical observations
  99. GRB 260310A/AT2026fgk: radio detection at 15GHz
  100. GRB 260310A / AT2026fgk: TNG NIR detection

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