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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 260616C: GECAM-B observation of a burst
  2. GRB 260618A: Fermi GBM Final Real-time Localization
  3. GRB 260617A: Fermi GBM Detection
  4. GRB 260616A: Fermi GBM Observation
  5. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  6. GRB 260617A: Fermi GBM Final Real-time Localization
  7. Konus-Wind detection of GRB 260616B/EP260616a
  8. Konus-Wind detection of GRB 260616A
  9. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  10. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  11. GRB 260616A: GECAM-B observation
  12. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  13. GRB 260429A: cubesat Avion detection
  14. GRB260616C: MAXI/GSC detection
  15. GRB 260616A: Fermi-LAT detection
  16. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  17. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  18. GRB 260614A: AstroSat CZTI detection
  19. EP260616a: EP-WXT detection of a fast X-ray transient
  20. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  21. The EP-WXT trigger 01709270148 is likely a flaring star
  22. GRB 260616B: Fermi GBM Detection
  23. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  24. GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
  25. The EP-WXT trigger 01709269893 is likely a flaring star
  26. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  27. GRB 260616A: Fermi GBM Final Real-time Localization
  28. GRB 260614B: SVOM/ECLAIRs refined analysis
  29. GRB 260610B: Terskol optical observations
  30. GRB 260614B: GECAM-B observation
  31. GRB 260610B: SVOM/GRM observation
  32. GRB 260614B: SVOM/VT optical afterglow confirmation
  33. GRB 260614B: Fermi GBM Observation
  34. GRB 260610B: ALMA detection
  35. GRB 260614A: GECAM-B observation
  36. GRB 260614B: SVOM/VT optical candidate from VHF data
  37. GRB 260614B: SVOM detection of a burst
  38. GRB 260614B: Fermi GBM Final Real-time Localization
  39. GRB 260611B: SVOM/GRM detection
  40. GRB 260614A: Fermi GBM Final Localization
  41. The EP-WXT trigger 01709269488 is likely a flaring star
  42. GRB 260603C: AstroSat CZTI detection
  43. GRB 260610B: further Liverpool Telescope optical observations
  44. GRB 260610B: Fermi GBM Observation
  45. GRB 260610B / AT2026owq: GRANDMA optical observations
  46. GRB 260610B / AT2026owq: further SAO RAS optical observations
  47. EP260605a: COLIBRÍ optical upper limits
  48. GRB 260610b: Liverpool Telescope optical observations
  49. EP260610b: Liverpool Telescope optical upper limits
  50. IceCube-260610A: No candidates from the Zwicky Transient Facility
  51. IceCube-260610A: EP-FXT follow-up observation
  52. GRB 260611B: CALET Gamma-Ray Burst Monitor detection
  53. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  54. GRB 260610B / AT2026owq: SVOM/VT optical observations
  55. GRB 260610B / AT2026owq: OASDG optical observations
  56. GRB 260610B: IAC-80 Optical observations
  57. GRB 260610B / AT2026owq: SAO RAS optical observations
  58. GRB 260611B: Fermi GBM Final Real-time Localization
  59. EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
  60. EP260610b: GTC likely spectroscopic redshift z = 1.10
  61. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  62. The EP-WXT trigger 01709269176 is likely a flaring star
  63. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  64. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  65. GRB 260610B / AT2026owq: Early ATLAS observations
  66. GRB 260610B: TRT optical observation
  67. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  68. GRB 260611A: Fermi GBM Final Real-time Localization
  69. EP260610b: COLIBRÍ optical observations
  70. GRB 260610B: DDOTI optical observations
  71. EP260610b: MAO/AZT-22 optical observations
  72. GRB 260610B: GOTO optical counterpart candidate
  73. EP260610b: NOT optical observation
  74. GRB 260610B: Fermi GBM Final Localization
  75. EP260610b: SVOM/VT optical confirmation with blue color
  76. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  77. GRB 260515A: SOAR optical observations
  78. EP260610b: Gemini North optical counterpart candidate
  79. EP260610a: SVOM/VT optical upper limits
  80. EP260610b: Einstein Probe detection of an X-ray transient
  81. Konus-Wind detection of GRB 260601A
  82. IPN triangulation of GRB 260601A (short/hard)
  83. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  84. GRB 260610A: Fermi GBM Final Real-time Localization
  85. EP260610a: COLIBRÍ optical upper limits
  86. EP260610a: Einstein Probe detection of a fast X-ray transient
  87. GRB 260609A: Fermi GBM Final Localization
  88. Konus-Wind detection of GRB 260604C
  89. GRB 260608A: Fermi GRB Observation
  90. GRB 260604C: AstroSat CZTI detection
  91. IPN triangulation of GRB 260601B / EP260601a
  92. GRB 260604C: SVOM/ECLAIRs refined analysis
  93. GRB 260608A: SVOM/ECLAIRs refined analysis
  94. Konus-Wind detection of GRB 260607B
  95. GRB 260607B: GECAM-B observation
  96. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  97. GRB 260608C: Fermi GBM Final Real-time Localization
  98. GRB 260604C: further SAO RAS optical observations
  99. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  100. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations

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