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

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