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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"

38258 results found.

  1. EP260321a: Chandra X-ray Non-detection
  2. GRB 260409A: Fermi GBM Final Real-time Localization
  3. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  4. GRB 260407A: GECAM-A detection
  5. GRB 260407A: Insight-HXMT/HE detection
  6. EP260409a: COLIBRÍ optical upper limits
  7. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  8. EP260409a: Global MASTER-Net observations report
  9. GRB 260404A: Fermi GBM Final Localization
  10. GRB 260407A: Glowbug gamma-ray detection
  11. GRB 260402A: SVOM/ECLAIRs refined analysis
  12. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  13. GRB 260310A / AT2026fgk: X-ray rebrightening
  14. EP260402a / GRB 260402A: Mephisto optical upper limits
  15. EP260403a: Mephisto optical upper limits
  16. EP260402a/GRB 260402A: Xinglong optical upper limit
  17. GRID detection of GRB 260401A
  18. GRB 260407A: Fermi GBM Final Real-time Localization
  19. EP260405a: Global MASTER-Net observations report
  20. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  21. Fermi trigger No 797039833: Global MASTER-Net observations report
  22. GRB 260403A: GECAM-B observation of a long burst
  23. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  24. GRB 260330B: SVOM/VT further optical observation
  25. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  26. GRB 260330B: SVOM/ECLAIRs refined analysis
  27. EP260403a: LCO optical observations of the counterpart
  28. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  29. EP260403a: LCO optical counterpart detection
  30. EP260403a: COLIBRÍ optical counterpart candidate
  31. GRB 260330B: SVOM/VT optical candidate
  32. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  33. GRB 260403A: AstroSat CZTI detection
  34. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  35. GRB 260402B: GECAM-B observation
  36. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  37. GRB 260402C: NuSTAR detection of prompt emission
  38. GRB 260402C: AstroSat CZTI detection of a long burst
  39. EP260324A / AT 2026hir: COLIBRÍ optical observations
  40. GRB 260403A: Fermi GBM Final Real-time Localization
  41. GRB 260402B: Fermi GBM Final Real-time Localization
  42. GRB 260402A: WINTER J-band upper limit
  43. GRB260402A: GROWTH-India Telescope optical upper limit
  44. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  45. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  46. GRB 260401A: SVOM/GRM observation
  47. GRB 260401A: GECAM-B observation
  48. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  49. GRB 260402A: Kilonova-Catcher optical upper limit
  50. GRB 260402A: MASTER optical observations
  51. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  52. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  53. GRB 260402A: SVOM detection of a burst
  54. Fermi GRB 260401A: Global MASTER-Net observations report
  55. GRB 260401A: Fermi GBM Observation
  56. GRB 260401A: NuSTAR detection of prompt emission
  57. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  58. GRB 260401A: MAXI/GSC detection
  59. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  60. GRB 260401A: Fermi GBM Final Real-time Localization
  61. EP260329b: Mondy and Assy-Turgen optical upper limits
  62. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  63. EP260321a :Xinglong optical observations
  64. EP260329b: GOTO detection of optical counterpart
  65. GRB 260330B: SVOM/VT optical upper limits
  66. Konus-Wind detection of GRB 260320A
  67. Konus-Wind detection of GRB 260316B (duplicate submission)
  68. Konus-Wind detection of GRB 260316B
  69. GRB 260321A: SVOM/ECLAIRs refined analysis
  70. EP260329b: J-band upper limits with WINTER
  71. EP260329a: J-band upper limit with WINTER
  72. GRB 260330A: Glowbug gamma-ray detection
  73. GRB 260310A: VLA Multi-frequency Radio Observations
  74. Fermi GBM Sub-Threshold Detection of GRB 260330B
  75. GRB 260330B: LCO optical upper limits
  76. GRB 260330B: SVOM detection of a burst
  77. EP260329a: COLIBRÍ optical upper limit
  78. GRB 260330A: Fermi GBM Final Real-time Localization
  79. EP260329b: Global MASTER-Net observations report
  80. Fermi trigger No 796485221: Global MASTER-Net observations report
  81. GRB 260327A: Insight-HXMT/HE detection
  82. EP 260329b: COLIBRÍ optical observations
  83. EP260329b: LCO optical observations of the counterpart
  84. GRB 260326A: Insight-HXMT/HE detection
  85. EP-WXT trigger 01709259209: TRT optical counterpart detection
  86. GRID detection of GRB 260326A
  87. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  88. SMA Detection of GRB 260310A / AT 2026fgk
  89. GRB 260307B: ATCA Radio Upper Limits
  90. EP260327a: COLIBRÍ optical upper limits
  91. GRB 260327A: AstroSat CZTI detection of a long burst
  92. EP260324a: GROWTH-India Telescope optical observation
  93. EP260327a: Global MASTER-Net observations report
  94. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  95. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  96. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  97. IPN triangulation of GRB 260320A
  98. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  99. GRB 260326A: Fermi GBM Detection
  100. EP260321a: JinShan near-infrared observations

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