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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"

11539 results found.

  1. GRB 260330B: SVOM/VT optical candidate
  2. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  3. GRB 260403A: AstroSat CZTI detection
  4. GRB 260402B: GECAM-B observation
  5. GRB 260403A: Fermi GBM Final Real-time Localization
  6. GRB 260402B: Fermi GBM Final Real-time Localization
  7. GRB 260401A: SVOM/GRM observation
  8. GRB 260401A: GECAM-B observation
  9. Fermi GRB 260401A: Global MASTER-Net observations report
  10. GRB 260401A: Fermi GBM Observation
  11. GRB 260401A: NuSTAR detection of prompt emission
  12. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  13. GRB 260401A: MAXI/GSC detection
  14. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  15. GRB 260401A: Fermi GBM Final Real-time Localization
  16. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  17. GRB 260330B: SVOM/VT optical upper limits
  18. Konus-Wind detection of GRB 260316B
  19. GRB 260321A: SVOM/ECLAIRs refined analysis
  20. GRB 260330A: Glowbug gamma-ray detection
  21. GRB 260310A: VLA Multi-frequency Radio Observations
  22. Fermi GBM Sub-Threshold Detection of GRB 260330B
  23. GRB 260330A: Fermi GBM Final Real-time Localization
  24. Fermi trigger No 796485221: Global MASTER-Net observations report
  25. GRB 260326A: Insight-HXMT/HE detection
  26. GRID detection of GRB 260326A
  27. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  28. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  29. GRB 260326A: Fermi GBM Detection
  30. GRB 260325A: Fermi GBM Final Localization
  31. GRB 260326A: Fermi GBM Final Real-time Localization
  32. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  33. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  34. IPN triangulation of GRB 260316B
  35. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  36. GRB 260310A: LBT optical observations
  37. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  38. Fermi GRB 260323A: Global MASTER-Net observations report
  39. GRB 260323A: Fermi GBM Final Real-time Localization
  40. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  41. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  42. GRB 260322A: Fermi GBM Final Localization
  43. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  44. GRB 260310A: continued optical observation at Mondy
  45. Fermi GBM Sub-Threshold Detection of GRB 260321A
  46. GRB 260318A: Glowbug gamma-ray detection
  47. GRB 260310A / AT 2026fgk: KAIT optical observations
  48. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  49. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  50. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  51. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  52. GRB 260310A/AT2026fgk: LBT near-infrared observations
  53. GRB 260318A: SVOM/GRM observation
  54. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  55. GRB 260318A: GECAM-B observation
  56. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  57. Fermi GRB 260318A: Global MASTER-Net observations report
  58. GRB 260318A: Fermi GBM Final Real-time Localization
  59. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  60. GRB 260310A / AT 2026fgk: radio detection with the VLA
  61. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  62. GRB 260310A / AT2026fgk: LCO optical observations
  63. GRB 260317A: Fermi GBM Final Localization
  64. GRB 260316B: GECAM-B observation
  65. GRB 260316B: SVOM/GRM observation
  66. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  67. EP260316a: COLIBRÍ faint optical counterpart candidate
  68. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  69. GRB 260316B: AstroSat CZTI detection
  70. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  71. GRB 260316B: Fermi GBM Final Real-time Localization
  72. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  73. GRB 260314A: Glowbug gamma-ray detection
  74. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  75. GRB 260310A / AT 2026fgk: iTelescope optical observations
  76. GRID detection of GRB 260312B
  77. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  78. Fermi trigger No 795185313: Global MASTER-Net observations report
  79. GRB 260314A: GECAM-B observation of a burst
  80. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  81. GRB 260310A / AT2026fgk: SAO RAS optical observations
  82. GRB 260310A/AT2026fgk: radio detection at 15GHz
  83. GRB 260310A / AT2026fgk: TNG NIR detection
  84. GRB 260310A / AT2026fgk: OASDG optical observations
  85. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  86. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  87. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  88. Fermi GRB 260314A: Global MASTER-Net observations report
  89. Fermi GRB 260313A: Global MASTER-Net observations report
  90. GRB 260314A: Fermi GBM Final Real-time Localization
  91. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  92. GRB 260313A: A Correction to the Fermi GBM Final Localization
  93. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  94. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  95. GRB 260310B: Insight-HXMT/HE detection
  96. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  97. GRB 260312B: AstroSat CZTI detection
  98. GRB 260313A: Fermi GBM Final Real-time Localization
  99. GRB 260308A: Insight-HXMT/HE detection
  100. GRB 260307A: CALET Gamma-Ray Burst Monitor detection

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