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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"

27770 results found.

  1. GRB260708B: MAXI/GSC detection
  2. GRB 260708A: Fermi-LAT detection
  3. GRB 260708A: Fermi-GBM detection
  4. GRB 260706A: Further EP-FXT follow-up observation
  5. GRB 260706A: SVOM/VT optical upper limits
  6. EP260707a: Einstein Probe detection of an X-ray transient
  7. Nova AT2026oyp (ASASSN-26dt): Pre-outburst Swift UVOT observation
  8. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  9. GRB 260705C: Glowbug gamma-ray detection of a short burst
  10. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  11. IceCube-260704A: No candidates from the Zwicky Transient Facility
  12. GRB 260707A: Fermi GBM Final Real-time Localization
  13. GRB 260706A: SVOM detection of a burst
  14. GRB 260706A: Fermi GBM Final Real-time Localization
  15. GRB 260705C: Fermi GBM Final Localization
  16. GRB 260705B: Fermi GBM Final Real-time Localization
  17. Fermi GBM Sub-Threshold Detection of GRB 260705A
  18. GRB 260705A: SVOM detection of a burst
  19. IceCube-260704A - IceCube observation of a high-energy neutrino candidate track-like event
  20. GRB 260629A: AstroSat CZTI detection
  21. EP260703a: EP-FXT follow-up observation
  22. GRB 260704A: SVOM detection of a possible GRB
  23. GRB 260703B: Fermi GBM Final Localization
  24. EP260703a: EP-WXT detection of a fast X-ray transient
  25. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  26. GRB 260703A: Fermi GBM Final Localization
  27. GRB 260610B: VLA detection
  28. GRB 260623A: Glowbug gamma-ray detection
  29. GRB 260701A: Fermi GBM Final Real-time Localization
  30. EP260628a: EP-FXT follow-up observation
  31. GRB 260629A: Fermi GBM Final Real-time Localization
  32. EP260628a: EP-WXT detection of a fast X-ray transient
  33. GRB 260628A: Fermi GBM Final Real-time Localization
  34. EP260626a: EP-FXT follow-up observation
  35. EP260626a: Liverpool Telescope upper limits
  36. EP260626a: EP-WXT detection of a fast X-ray transient
  37. Konus-Wind detection of GRB 260623B / EP260623a
  38. EP260623a: TNG NIR afterglow detection
  39. MASS-Cube (GRID 2.0) detection of GRB 260616B
  40. Konus-Wind detection of GRB 260618B
  41. GRB 260624A: Fermi GBM Final Real-time Localization
  42. GRB 260617A: Glowbug gamma-ray detection of a short burst
  43. IPN triangulation of GRB 260605A
  44. EP260623a: Optical follow-up observations with Kinder
  45. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  46. GRB 260623A: Fermi GBM Final Real-time Localization
  47. EP260623a: REM optical/NIR afterglow detection
  48. EP 260623a: COLIBRÍ optical observations
  49. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  50. EP260623a: Einstein Probe detection of an X-ray transient
  51. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  52. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  53. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  54. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  55. GRB 260604B: 239Alferov CubeSat detection
  56. GRB 260604A: 239Alferov CubeSat detection
  57. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  58. Konus-Wind detection of GRB 260617A
  59. GRB 260616B: AstroSat CZTI detection
  60. GRB 260616A: AstroSat CZTI detection
  61. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  62. EP260618a: EP-FXT follow-up observation
  63. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  64. GRB 260616A: NuSTAR detection of prompt emission
  65. GRB 260614B: NuSTAR detection of prompt emission
  66. GRB 260619A: SVOM possible detection of a faint burst
  67. GRB 260618B: Fermi-LAT detection
  68. IPN triangulation of GRB 260617A (short)
  69. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  70. GRB 260616A: Insight-HXMT detection
  71. GRB 260618B: Fermi GBM Final Real-time Localization
  72. EP260618a: EP-WXT detection of an X-ray transient
  73. EP260616a/GRB 260616B: EP-FXT follow-up observation
  74. GRB 260506B: cubesat Avion detection
  75. GRB 260618A: Fermi GBM Final Real-time Localization
  76. GRB 260617A: Fermi GBM Detection
  77. GRB 260617A: Fermi GBM Final Real-time Localization
  78. Konus-Wind detection of GRB 260616B/EP260616a
  79. Konus-Wind detection of GRB 260616A
  80. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  81. GRB 260429A: cubesat Avion detection
  82. GRB260616C: MAXI/GSC detection
  83. GRB 260616A: Fermi-LAT detection
  84. GRB 260614A: AstroSat CZTI detection
  85. EP260616a: EP-WXT detection of a fast X-ray transient
  86. GRB 260616B: Fermi GBM Detection
  87. GRB 260616A: Fermi GBM Final Real-time Localization
  88. GRB 260610B: ALMA detection
  89. GRB 260614B: SVOM detection of a burst
  90. GRB 260614B: Fermi GBM Final Real-time Localization
  91. GRB 260611B: SVOM/GRM detection
  92. GRB 260614A: Fermi GBM Final Localization
  93. GRB 260603C: AstroSat CZTI detection
  94. EP260610b: Liverpool Telescope optical upper limits
  95. GRB 260611B: CALET Gamma-Ray Burst Monitor detection
  96. GRB 260611B: Fermi GBM Final Real-time Localization
  97. GRB 260610B / AT2026owq: Early ATLAS observations
  98. GRB 260611A: Fermi GBM Final Real-time Localization
  99. GRB 260610B: Fermi GBM Final Localization
  100. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event

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