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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 260617A: Glowbug gamma-ray detection of a short burst
  2. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  3. IPN triangulation of GRB 260605A
  4. EP260623a: Optical follow-up observations with Kinder
  5. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  6. GRB 260623A: Fermi GBM Final Real-time Localization
  7. EP260623a: SVOM/VT optical observations
  8. EP260623a: TRT optical observations
  9. EP260623a: REM optical/NIR afterglow detection
  10. EP 260623a: COLIBRÍ optical observations
  11. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  12. EP260623a: OSIRIS+/GTC redshift z = 0.703
  13. EP260623a: Las Cumbres discovery of the optical counterpart
  14. EP260623a: Einstein Probe detection of an X-ray transient
  15. GRB 260614B: EP-FXT follow-up observation
  16. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  17. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  18. EP260618a: Liverpool Telescope optical observations
  19. GRB 260619A: NOT optical observations
  20. GRB 260618B: LCO optical observations
  21. The EP-WXT trigger 01709271197 is likely a flaring star
  22. EP260618a: JinShan optical observations
  23. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  24. GRB 260618B: Fermi GBM Observation
  25. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  26. GRB 260619A: TRT optical counterpart confirmation
  27. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  28. GRB 260604B: 239Alferov CubeSat detection
  29. GRB 260604A: 239Alferov CubeSat detection
  30. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  31. GRB 260619A: SVOM/VT optical counterpart confirmation
  32. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  33. GRB 260618B: SVOM/VT optical candidate
  34. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  35. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  36. Konus-Wind detection of GRB 260617A
  37. GRB 260616B: AstroSat CZTI detection
  38. GRB 260616A: AstroSat CZTI detection
  39. GRB 260616A: SVOM/GRM observation
  40. EP260618a: OHP/T193 optical observations
  41. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  42. GRB 260619A: Kilonova-Catcher optical upper limit
  43. EP260618a: EP-FXT follow-up observation
  44. EP260618a: LCO optical counterpart confirmation
  45. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  46. EP260618a: COLIBRÍ optical counterpart candidate
  47. GRB 260616A: NuSTAR detection of prompt emission
  48. GRB 260614B: NuSTAR detection of prompt emission
  49. GRB 260619A: SVOM possible detection of a faint burst
  50. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  51. GRB 260618B: Fermi-LAT detection
  52. IPN triangulation of GRB 260617A (short)
  53. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  54. GRB 260616A: Insight-HXMT detection
  55. GRB 260618B: Fermi GBM Final Real-time Localization
  56. EP260618a: EP-WXT detection of an X-ray transient
  57. GRB 260610B: AbAO optical observations
  58. EP260616a/GRB 260616B: EP-FXT follow-up observation
  59. GRB 260506B: cubesat Avion detection
  60. GRB 260616C: GECAM-B observation of a burst
  61. GRB 260618A: Fermi GBM Final Real-time Localization
  62. GRB 260617A: Fermi GBM Detection
  63. GRB 260616A: Fermi GBM Observation
  64. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  65. GRB 260617A: Fermi GBM Final Real-time Localization
  66. Konus-Wind detection of GRB 260616B/EP260616a
  67. Konus-Wind detection of GRB 260616A
  68. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  69. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  70. GRB 260616A: GECAM-B observation
  71. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  72. GRB 260429A: cubesat Avion detection
  73. GRB260616C: MAXI/GSC detection
  74. GRB 260616A: Fermi-LAT detection
  75. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  76. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  77. GRB 260614A: AstroSat CZTI detection
  78. EP260616a: EP-WXT detection of a fast X-ray transient
  79. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  80. The EP-WXT trigger 01709270148 is likely a flaring star
  81. GRB 260616B: Fermi GBM Detection
  82. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  83. GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
  84. The EP-WXT trigger 01709269893 is likely a flaring star
  85. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  86. GRB 260616A: Fermi GBM Final Real-time Localization
  87. GRB 260614B: SVOM/ECLAIRs refined analysis
  88. GRB 260610B: Terskol optical observations
  89. GRB 260614B: GECAM-B observation
  90. GRB 260610B: SVOM/GRM observation
  91. GRB 260614B: SVOM/VT optical afterglow confirmation
  92. GRB 260614B: Fermi GBM Observation
  93. GRB 260610B: ALMA detection
  94. GRB 260614A: GECAM-B observation
  95. GRB 260614B: SVOM/VT optical candidate from VHF data
  96. GRB 260614B: SVOM detection of a burst
  97. GRB 260614B: Fermi GBM Final Real-time Localization
  98. GRB 260611B: SVOM/GRM detection
  99. GRB 260614A: Fermi GBM Final Localization
  100. The EP-WXT trigger 01709269488 is likely a flaring star

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