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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

39257 results found.

  1. GRB 260409A: Fermi GBM Final Real-time Localization
  2. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  3. GRB 260407A: GECAM-A detection
  4. GRB 260407A: Insight-HXMT/HE detection
  5. EP260409a: COLIBRÍ optical upper limits
  6. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  7. EP260409a: Global MASTER-Net observations report
  8. GRB 260404A: Fermi GBM Final Localization
  9. GRB 260407A: Glowbug gamma-ray detection
  10. GRB 260402A: SVOM/ECLAIRs refined analysis
  11. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  12. GRB 260310A / AT2026fgk: X-ray rebrightening
  13. EP260402a / GRB 260402A: Mephisto optical upper limits
  14. EP260403a: Mephisto optical upper limits
  15. EP260402a/GRB 260402A: Xinglong optical upper limit
  16. GRID detection of GRB 260401A
  17. GRB 260407A: Fermi GBM Final Real-time Localization
  18. EP260405a: Global MASTER-Net observations report
  19. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  20. Fermi trigger No 797039833: Global MASTER-Net observations report
  21. GRB 260403A: GECAM-B observation of a long burst
  22. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  23. GRB 260330B: SVOM/VT further optical observation
  24. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  25. GRB 260330B: SVOM/ECLAIRs refined analysis
  26. EP260403a: LCO optical observations of the counterpart
  27. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  28. EP260403a: LCO optical counterpart detection
  29. EP260403a: COLIBRÍ optical counterpart candidate
  30. GRB 260330B: SVOM/VT optical candidate
  31. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  32. GRB 260403A: AstroSat CZTI detection
  33. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  34. GRB 260402B: GECAM-B observation
  35. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  36. GRB 260402C: NuSTAR detection of prompt emission
  37. GRB 260402C: AstroSat CZTI detection of a long burst
  38. EP260324A / AT 2026hir: COLIBRÍ optical observations
  39. GRB 260403A: Fermi GBM Final Real-time Localization
  40. GRB 260402B: Fermi GBM Final Real-time Localization
  41. GRB 260402A: WINTER J-band upper limit
  42. GRB260402A: GROWTH-India Telescope optical upper limit
  43. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  44. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  45. GRB 260401A: SVOM/GRM observation
  46. GRB 260401A: GECAM-B observation
  47. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  48. GRB 260402A: Kilonova-Catcher optical upper limit
  49. GRB 260402A: MASTER optical observations
  50. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  51. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  52. GRB 260402A: SVOM detection of a burst
  53. Fermi GRB 260401A: Global MASTER-Net observations report
  54. GRB 260401A: Fermi GBM Observation
  55. GRB 260401A: NuSTAR detection of prompt emission
  56. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  57. GRB 260401A: MAXI/GSC detection
  58. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  59. GRB 260401A: Fermi GBM Final Real-time Localization
  60. EP260329b: Mondy and Assy-Turgen optical upper limits
  61. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  62. EP260321a :Xinglong optical observations
  63. EP260329b: GOTO detection of optical counterpart
  64. GRB 260330B: SVOM/VT optical upper limits
  65. Konus-Wind detection of GRB 260320A
  66. Konus-Wind detection of GRB 260316B (duplicate submission)
  67. Konus-Wind detection of GRB 260316B
  68. GRB 260321A: SVOM/ECLAIRs refined analysis
  69. EP260329b: J-band upper limits with WINTER
  70. EP260329a: J-band upper limit with WINTER
  71. GRB 260330A: Glowbug gamma-ray detection
  72. GRB 260310A: VLA Multi-frequency Radio Observations
  73. Fermi GBM Sub-Threshold Detection of GRB 260330B
  74. GRB 260330B: LCO optical upper limits
  75. GRB 260330B: SVOM detection of a burst
  76. EP260329a: COLIBRÍ optical upper limit
  77. GRB 260330A: Fermi GBM Final Real-time Localization
  78. EP260329b: Global MASTER-Net observations report
  79. Fermi trigger No 796485221: Global MASTER-Net observations report
  80. GRB 260327A: Insight-HXMT/HE detection
  81. EP 260329b: COLIBRÍ optical observations
  82. EP260329b: LCO optical observations of the counterpart
  83. GRB 260326A: Insight-HXMT/HE detection
  84. EP-WXT trigger 01709259209: TRT optical counterpart detection
  85. GRID detection of GRB 260326A
  86. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  87. SMA Detection of GRB 260310A / AT 2026fgk
  88. GRB 260307B: ATCA Radio Upper Limits
  89. EP260327a: COLIBRÍ optical upper limits
  90. GRB 260327A: AstroSat CZTI detection of a long burst
  91. EP260324a: GROWTH-India Telescope optical observation
  92. EP260327a: Global MASTER-Net observations report
  93. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  94. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  95. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  96. IPN triangulation of GRB 260320A
  97. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  98. GRB 260326A: Fermi GBM Detection
  99. EP260321a: JinShan near-infrared observations
  100. GRB 260325A: Fermi GBM Final Localization

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