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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"
  1. GRB 260629A: Fermi GBM Final Real-time Localization
  2. Fermi GRB 260628A: Global MASTER-Net observations report
  3. EP260628a: EP-WXT detection of a fast X-ray transient
  4. GRB 260628A: Fermi GBM Final Real-time Localization
  5. The EP-WXT trigger 01709272671 is likely a flaring star
  6. EP260626a: further Liverpool Telescope optical upper limits
  7. EP260626a: EP-FXT follow-up observation
  8. EP260626a: COLIBRÍ optical upper limit
  9. EP260626a: Liverpool Telescope upper limits
  10. EP260626a: EP-WXT detection of a fast X-ray transient
  11. Konus-Wind detection of GRB 260623B / EP260623a
  12. EP260623a: TNG NIR afterglow detection
  13. GRB 260618A: Fermi GBM Observation
  14. MASS-Cube (GRID 2.0) detection of GRB 260616B
  15. EP260623a: FTW optical and NIR observations
  16. GRB 260619A: SVOM/ECLAIRs refined analysis
  17. EP260623a: Liverpool Telescope optical observations
  18. Fermi GBM trigger 804010507/260624677 is not a GRB
  19. Konus-Wind detection of GRB 260618B
  20. GRB 260624A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  21. GRB 260624A: Fermi GBM Final Real-time Localization
  22. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  23. EP260623a: WINTER J-band observations
  24. GRB 260617A: Glowbug gamma-ray detection of a short burst
  25. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  26. IPN triangulation of GRB 260605A
  27. EP260623a: Optical follow-up observations with Kinder
  28. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  29. GRB 260623A: Fermi GBM Final Real-time Localization
  30. EP260623a: SVOM/VT optical observations
  31. EP260623a: TRT optical observations
  32. EP260623a: REM optical/NIR afterglow detection
  33. EP 260623a: COLIBRÍ optical observations
  34. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  35. EP260623a: OSIRIS+/GTC redshift z = 0.703
  36. EP260623a: Las Cumbres discovery of the optical counterpart
  37. EP260623a: Einstein Probe detection of an X-ray transient
  38. GRB 260614B: EP-FXT follow-up observation
  39. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  40. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  41. EP260618a: Liverpool Telescope optical observations
  42. GRB 260619A: NOT optical observations
  43. GRB 260618B: LCO optical observations
  44. The EP-WXT trigger 01709271197 is likely a flaring star
  45. EP260618a: JinShan optical observations
  46. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  47. GRB 260618B: Fermi GBM Observation
  48. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  49. GRB 260619A: TRT optical counterpart confirmation
  50. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  51. GRB 260604B: 239Alferov CubeSat detection
  52. GRB 260604A: 239Alferov CubeSat detection
  53. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  54. GRB 260619A: SVOM/VT optical counterpart confirmation
  55. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  56. GRB 260618B: SVOM/VT optical candidate
  57. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  58. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  59. Konus-Wind detection of GRB 260617A
  60. GRB 260616B: AstroSat CZTI detection
  61. GRB 260616A: AstroSat CZTI detection
  62. GRB 260616A: SVOM/GRM observation
  63. EP260618a: OHP/T193 optical observations
  64. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  65. GRB 260619A: Kilonova-Catcher optical upper limit
  66. EP260618a: EP-FXT follow-up observation
  67. EP260618a: LCO optical counterpart confirmation
  68. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  69. EP260618a: COLIBRÍ optical counterpart candidate
  70. GRB 260616A: NuSTAR detection of prompt emission
  71. GRB 260614B: NuSTAR detection of prompt emission
  72. GRB 260619A: SVOM possible detection of a faint burst
  73. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  74. GRB 260618B: Fermi-LAT detection
  75. IPN triangulation of GRB 260617A (short)
  76. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  77. GRB 260616A: Insight-HXMT detection
  78. GRB 260618B: Fermi GBM Final Real-time Localization
  79. EP260618a: EP-WXT detection of an X-ray transient
  80. GRB 260610B: AbAO optical observations
  81. EP260616a/GRB 260616B: EP-FXT follow-up observation
  82. GRB 260506B: cubesat Avion detection
  83. GRB 260616C: GECAM-B observation of a burst
  84. GRB 260618A: Fermi GBM Final Real-time Localization
  85. GRB 260617A: Fermi GBM Detection
  86. GRB 260616A: Fermi GBM Observation
  87. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  88. GRB 260617A: Fermi GBM Final Real-time Localization
  89. Konus-Wind detection of GRB 260616B/EP260616a
  90. Konus-Wind detection of GRB 260616A
  91. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  92. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  93. GRB 260616A: GECAM-B observation
  94. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  95. GRB 260429A: cubesat Avion detection
  96. GRB260616C: MAXI/GSC detection
  97. GRB 260616A: Fermi-LAT detection
  98. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  99. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  100. GRB 260614A: AstroSat CZTI detection

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