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

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