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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"

12283 results found.

  1. GRB 260410B: SVOM/GRM detection of a short faint burst
  2. GRB 260410B: Fermi GBM Final Real-time Localization
  3. GRB 260410A: Fermi-LAT detection
  4. GRB 260410A: Fermi GBM Final Real-time Localization
  5. GRB 260409A: Fermi GBM Final Real-time Localization
  6. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  7. GRB 260407A: GECAM-A detection
  8. GRB 260407A: Insight-HXMT/HE detection
  9. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  10. GRB 260404A: Fermi GBM Final Localization
  11. GRB 260407A: Glowbug gamma-ray detection
  12. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  13. GRB 260310A / AT2026fgk: X-ray rebrightening
  14. GRID detection of GRB 260401A
  15. GRB 260407A: Fermi GBM Final Real-time Localization
  16. Fermi trigger No 797039833: Global MASTER-Net observations report
  17. GRB 260403A: GECAM-B observation of a long burst
  18. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  19. GRB 260330B: SVOM/VT further optical observation
  20. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  21. GRB 260330B: SVOM/ECLAIRs refined analysis
  22. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  23. GRB 260330B: SVOM/VT optical candidate
  24. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  25. GRB 260403A: AstroSat CZTI detection
  26. GRB 260402B: GECAM-B observation
  27. GRB 260403A: Fermi GBM Final Real-time Localization
  28. GRB 260402B: Fermi GBM Final Real-time Localization
  29. GRB 260401A: SVOM/GRM observation
  30. GRB 260401A: GECAM-B observation
  31. Fermi GRB 260401A: Global MASTER-Net observations report
  32. GRB 260401A: Fermi GBM Observation
  33. GRB 260401A: NuSTAR detection of prompt emission
  34. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  35. GRB 260401A: MAXI/GSC detection
  36. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  37. GRB 260401A: Fermi GBM Final Real-time Localization
  38. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  39. GRB 260330B: SVOM/VT optical upper limits
  40. Konus-Wind detection of GRB 260316B
  41. GRB 260321A: SVOM/ECLAIRs refined analysis
  42. GRB 260330A: Glowbug gamma-ray detection
  43. GRB 260310A: VLA Multi-frequency Radio Observations
  44. Fermi GBM Sub-Threshold Detection of GRB 260330B
  45. GRB 260330A: Fermi GBM Final Real-time Localization
  46. Fermi trigger No 796485221: Global MASTER-Net observations report
  47. GRB 260326A: Insight-HXMT/HE detection
  48. GRID detection of GRB 260326A
  49. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  50. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  51. GRB 260326A: Fermi GBM Detection
  52. GRB 260325A: Fermi GBM Final Localization
  53. GRB 260326A: Fermi GBM Final Real-time Localization
  54. EP260321a: Upper limits from a neutrino search with IceCube
  55. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  56. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  57. IPN triangulation of GRB 260316B
  58. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  59. GRB 260310A: LBT optical observations
  60. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  61. Fermi GRB 260323A: Global MASTER-Net observations report
  62. GRB 260323A: Fermi GBM Final Real-time Localization
  63. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  64. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  65. GRB 260322A: Fermi GBM Final Localization
  66. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  67. GRB 260310A: continued optical observation at Mondy
  68. Fermi GBM Sub-Threshold Detection of GRB 260321A
  69. GRB 260318A: Glowbug gamma-ray detection
  70. GRB 260310A / AT 2026fgk: KAIT optical observations
  71. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  72. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  73. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  74. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  75. GRB 260310A/AT2026fgk: LBT near-infrared observations
  76. GRB 260318A: SVOM/GRM observation
  77. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  78. GRB 260318A: GECAM-B observation
  79. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  80. Fermi GRB 260318A: Global MASTER-Net observations report
  81. GRB 260318A: Fermi GBM Final Real-time Localization
  82. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  83. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  84. GRB 260310A / AT 2026fgk: radio detection with the VLA
  85. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  86. GRB 260310A / AT2026fgk: LCO optical observations
  87. GRB 260317A: Fermi GBM Final Localization
  88. GRB 260316B: GECAM-B observation
  89. GRB 260316B: SVOM/GRM observation
  90. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  91. EP260316a: COLIBRÍ faint optical counterpart candidate
  92. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  93. GRB 260316B: AstroSat CZTI detection
  94. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  95. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  96. GRB 260316B: Fermi GBM Final Real-time Localization
  97. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  98. GRB 260314A: Glowbug gamma-ray detection
  99. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  100. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations

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