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

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