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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"

14853 results found.

  1. GRB 260411A: Fermi GBM Final Real-time Localization
  2. EP-WXT01709259790: Optical Upper limits with kinder observations
  3. GRB 260410B: SVOM/GRM detection of a short faint burst
  4. GRB 260410B: Fermi GBM Final Real-time Localization
  5. EP-WXT01709259790: Xinglong optical upper limit
  6. GRB 260410A: Fermi-LAT detection
  7. GRB 260410A: Fermi GBM Final Real-time Localization
  8. EP260321a: Chandra X-ray Non-detection
  9. GRB 260409A: Fermi GBM Final Real-time Localization
  10. GRB 260407A: GECAM-A detection
  11. GRB 260407A: Insight-HXMT/HE detection
  12. EP260409a: SVOM/VT optical upper limits
  13. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  14. EP260409a: Einstein Probe detection of an X-ray transient
  15. EP260321a: VLA radio detection
  16. GRB 260404A: Fermi GBM Final Localization
  17. GRB 260407A: Glowbug gamma-ray detection
  18. GRB 260310A / AT2026fgk: X-ray rebrightening
  19. EP260402a / GRB 260402A: Mephisto optical upper limits
  20. EP-WXT01709259586: Xinglong optical upper limit
  21. EP260403a: Mephisto optical upper limits
  22. EP260402a/GRB 260402A: Xinglong optical upper limit
  23. EP260321a: Upper limits from VLA radio observations
  24. GRID detection of GRB 260401A
  25. EP260321a: uGMRT observations
  26. GRB 260407A: Fermi GBM Final Real-time Localization
  27. EP260405a: Einstein Probe detection of a fast X-ray transient
  28. GRB 260330B: SVOM/VT further optical observation
  29. EP260403a: LCO optical counterpart detection
  30. GRB 260330B: SVOM/VT optical candidate
  31. EP260403a: Einstein Probe detection of an X-ray transient
  32. GRB 260403A: AstroSat CZTI detection
  33. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  34. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  35. GRB 260402C: NuSTAR detection of prompt emission
  36. GRB 260402C: AstroSat CZTI detection of a long burst
  37. GRB 260403A: Fermi GBM Final Real-time Localization
  38. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  39. GRB 260402B: Fermi GBM Final Real-time Localization
  40. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  41. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  42. GRB 260402A: SVOM detection of a burst
  43. GRB 260401A: NuSTAR detection of prompt emission
  44. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  45. GRB 260401A: MAXI/GSC detection
  46. GRB 260401A: Fermi GBM Final Real-time Localization
  47. EP260327a: Xinglong optical upper limit
  48. EP260329b: GOTO detection of optical counterpart
  49. GRB 260330B: SVOM/VT optical upper limits
  50. Konus-Wind detection of GRB 260320A
  51. Konus-Wind detection of GRB 260316B (duplicate submission)
  52. Konus-Wind detection of GRB 260316B
  53. GRB 260321A: SVOM/ECLAIRs refined analysis
  54. EP260329a: J-band upper limit with WINTER
  55. GRB 260330A: Glowbug gamma-ray detection
  56. Fermi GBM Sub-Threshold Detection of GRB 260330B
  57. GRB 260330B: SVOM detection of a burst
  58. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  59. EP260329a: COLIBRÍ optical upper limit
  60. EP260329a: EP-FXT follow up observation
  61. EP260329a: NOT optical counterpart candidate
  62. GRB 260330A: Fermi GBM Final Real-time Localization
  63. GRB 260327A: Insight-HXMT/HE detection
  64. EP260329b: Optical follow-up with Kinder observations
  65. EP260329a: Optical upper limit with Kinder observations
  66. GRB 260326A: Insight-HXMT/HE detection
  67. EP260329b: Einstein Probe detection of an X-ray transient
  68. EP260329a: Einstein Probe detection of an X-ray transient
  69. EP-WXT trigger 01709259209: TRT optical counterpart detection
  70. GRID detection of GRB 260326A
  71. EP260327a: SVOM/VT optical upper limits
  72. SMA Detection of GRB 260310A / AT 2026fgk
  73. GRB 260327A: AstroSat CZTI detection of a long burst
  74. EP260327a: Einstein Probe detection of an X-ray transient
  75. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  76. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  77. IPN triangulation of GRB 260320A
  78. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  79. GRB 260326A: Fermi GBM Detection
  80. EP260321a: JinShan near-infrared observations
  81. GRB 260325A: Fermi GBM Final Localization
  82. GRB 260326A: Fermi GBM Final Real-time Localization
  83. EP260321a: Upper limits from a neutrino search with IceCube
  84. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  85. IPN triangulation of GRB 260316B
  86. GRID detection of GRB 260320A
  87. EP260321a: Gemini-South confirmation of a supernova
  88. GRB 260310A: LBT optical observations
  89. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  90. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  91. GRB 260323A: Fermi GBM Final Real-time Localization
  92. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  93. GRB 260322A: Fermi GBM Final Localization
  94. GRB 260320A: Glowbug gamma-ray detection
  95. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  96. EP260321a: COLIBRÍ further optical observations and brightening
  97. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  98. EP260214b: ATCA 6 GHz detection
  99. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  100. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a

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