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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 260628A: Fermi GBM Final Real-time Localization
  2. The EP-WXT trigger 01709272671 is likely a flaring star
  3. EP260626a: further Liverpool Telescope optical upper limits
  4. EP260626a: EP-FXT follow-up observation
  5. EP260626a: COLIBRÍ optical upper limit
  6. EP260626a: Liverpool Telescope upper limits
  7. EP260626a: EP-WXT detection of a fast X-ray transient
  8. Konus-Wind detection of GRB 260623B / EP260623a
  9. EP260623a: TNG NIR afterglow detection
  10. GRB 260618A: Fermi GBM Observation
  11. MASS-Cube (GRID 2.0) detection of GRB 260616B
  12. EP260623a: FTW optical and NIR observations
  13. GRB 260619A: SVOM/ECLAIRs refined analysis
  14. EP260623a: Liverpool Telescope optical observations
  15. Fermi GBM trigger 804010507/260624677 is not a GRB
  16. Konus-Wind detection of GRB 260618B
  17. GRB 260624A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  18. GRB 260624A: Fermi GBM Final Real-time Localization
  19. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  20. EP260623a: WINTER J-band observations
  21. GRB 260617A: Glowbug gamma-ray detection of a short burst
  22. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  23. IPN triangulation of GRB 260605A
  24. EP260623a: Optical follow-up observations with Kinder
  25. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  26. GRB 260623A: Fermi GBM Final Real-time Localization
  27. EP260623a: SVOM/VT optical observations
  28. EP260623a: TRT optical observations
  29. EP260623a: REM optical/NIR afterglow detection
  30. EP 260623a: COLIBRÍ optical observations
  31. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  32. EP260623a: OSIRIS+/GTC redshift z = 0.703
  33. EP260623a: Las Cumbres discovery of the optical counterpart
  34. EP260623a: Einstein Probe detection of an X-ray transient
  35. GRB 260614B: EP-FXT follow-up observation
  36. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  37. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  38. EP260618a: Liverpool Telescope optical observations
  39. GRB 260619A: NOT optical observations
  40. GRB 260618B: LCO optical observations
  41. The EP-WXT trigger 01709271197 is likely a flaring star
  42. EP260618a: JinShan optical observations
  43. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  44. GRB 260618B: Fermi GBM Observation
  45. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  46. GRB 260619A: TRT optical counterpart confirmation
  47. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  48. GRB 260604B: 239Alferov CubeSat detection
  49. GRB 260604A: 239Alferov CubeSat detection
  50. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  51. GRB 260619A: SVOM/VT optical counterpart confirmation
  52. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  53. GRB 260618B: SVOM/VT optical candidate
  54. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  55. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  56. Konus-Wind detection of GRB 260617A
  57. GRB 260616B: AstroSat CZTI detection
  58. GRB 260616A: AstroSat CZTI detection
  59. GRB 260616A: SVOM/GRM observation
  60. EP260618a: OHP/T193 optical observations
  61. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  62. GRB 260619A: Kilonova-Catcher optical upper limit
  63. EP260618a: EP-FXT follow-up observation
  64. EP260618a: LCO optical counterpart confirmation
  65. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  66. EP260618a: COLIBRÍ optical counterpart candidate
  67. GRB 260616A: NuSTAR detection of prompt emission
  68. GRB 260614B: NuSTAR detection of prompt emission
  69. GRB 260619A: SVOM possible detection of a faint burst
  70. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  71. GRB 260618B: Fermi-LAT detection
  72. IPN triangulation of GRB 260617A (short)
  73. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  74. GRB 260616A: Insight-HXMT detection
  75. GRB 260618B: Fermi GBM Final Real-time Localization
  76. EP260618a: EP-WXT detection of an X-ray transient
  77. GRB 260610B: AbAO optical observations
  78. EP260616a/GRB 260616B: EP-FXT follow-up observation
  79. GRB 260506B: cubesat Avion detection
  80. GRB 260616C: GECAM-B observation of a burst
  81. GRB 260618A: Fermi GBM Final Real-time Localization
  82. GRB 260617A: Fermi GBM Detection
  83. GRB 260616A: Fermi GBM Observation
  84. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  85. GRB 260617A: Fermi GBM Final Real-time Localization
  86. Konus-Wind detection of GRB 260616B/EP260616a
  87. Konus-Wind detection of GRB 260616A
  88. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  89. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  90. GRB 260616A: GECAM-B observation
  91. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  92. GRB 260429A: cubesat Avion detection
  93. GRB260616C: MAXI/GSC detection
  94. GRB 260616A: Fermi-LAT detection
  95. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  96. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  97. GRB 260614A: AstroSat CZTI detection
  98. EP260616a: EP-WXT detection of a fast X-ray transient
  99. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  100. The EP-WXT trigger 01709270148 is likely a flaring star

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