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

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