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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"

45431 results found.

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

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