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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"

32532 results found.

  1. GRB 260618B: Fermi GBM Observation
  2. GRB 260619A: TRT optical counterpart confirmation
  3. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  4. GRB 260604B: 239Alferov CubeSat detection
  5. GRB 260604A: 239Alferov CubeSat detection
  6. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  7. GRB 260619A: SVOM/VT optical counterpart confirmation
  8. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  9. GRB 260618B: SVOM/VT optical candidate
  10. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  11. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  12. Konus-Wind detection of GRB 260617A
  13. GRB 260616B: AstroSat CZTI detection
  14. GRB 260616A: AstroSat CZTI detection
  15. GRB 260616A: SVOM/GRM observation
  16. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  17. GRB 260619A: Kilonova-Catcher optical upper limit
  18. EP260618a: EP-FXT follow-up observation
  19. EP260618a: LCO optical counterpart confirmation
  20. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  21. EP260618a: COLIBRÍ optical counterpart candidate
  22. GRB 260616A: NuSTAR detection of prompt emission
  23. GRB 260614B: NuSTAR detection of prompt emission
  24. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  25. GRB 260618B: Fermi-LAT detection
  26. IPN triangulation of GRB 260617A (short)
  27. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  28. GRB 260616A: Insight-HXMT detection
  29. EP260618a: EP-WXT detection of an X-ray transient
  30. GRB 260610B: AbAO optical observations
  31. EP260616a/GRB 260616B: EP-FXT follow-up observation
  32. GRB 260506B: cubesat Avion detection
  33. GRB 260616C: GECAM-B observation of a burst
  34. GRB 260616A: Fermi GBM Observation
  35. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  36. Konus-Wind detection of GRB 260616B/EP260616a
  37. Konus-Wind detection of GRB 260616A
  38. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  39. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  40. GRB 260616A: GECAM-B observation
  41. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  42. GRB 260429A: cubesat Avion detection
  43. GRB 260616A: Fermi-LAT detection
  44. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  45. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  46. GRB 260614A: AstroSat CZTI detection
  47. EP260616a: EP-WXT detection of a fast X-ray transient
  48. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  49. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  50. GRB 260614B: SVOM/ECLAIRs refined analysis
  51. GRB 260610B: Terskol optical observations
  52. GRB 260614B: GECAM-B observation
  53. GRB 260610B: SVOM/GRM observation
  54. GRB 260614B: SVOM/VT optical afterglow confirmation
  55. GRB 260614B: Fermi GBM Observation
  56. GRB 260610B: ALMA detection
  57. GRB 260614A: GECAM-B observation
  58. GRB 260614B: SVOM/VT optical candidate from VHF data
  59. GRB 260614B: SVOM detection of a burst
  60. GRB 260611B: SVOM/GRM detection
  61. GRB 260610B: further Liverpool Telescope optical observations
  62. GRB 260610B: Fermi GBM Observation
  63. GRB 260610B / AT2026owq: GRANDMA optical observations
  64. GRB 260610B / AT2026owq: further SAO RAS optical observations
  65. EP260605a: COLIBRÍ optical upper limits
  66. GRB 260610b: Liverpool Telescope optical observations
  67. EP260610b: Liverpool Telescope optical upper limits
  68. IceCube-260610A: No candidates from the Zwicky Transient Facility
  69. IceCube-260610A: EP-FXT follow-up observation
  70. GRB 260611B: CALET Gamma-Ray Burst Monitor detection
  71. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  72. GRB 260610B / AT2026owq: SVOM/VT optical observations
  73. GRB 260610B / AT2026owq: OASDG optical observations
  74. GRB 260610B: IAC-80 Optical observations
  75. GRB 260610B / AT2026owq: SAO RAS optical observations
  76. EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
  77. EP260610b: GTC likely spectroscopic redshift z = 1.10
  78. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  79. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  80. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  81. GRB 260610B / AT2026owq: Early ATLAS observations
  82. GRB 260610B: TRT optical observation
  83. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  84. EP260610b: COLIBRÍ optical observations
  85. GRB 260610B: DDOTI optical observations
  86. EP260610b: MAO/AZT-22 optical observations
  87. GRB 260610B: GOTO optical counterpart candidate
  88. EP260610b: NOT optical observation
  89. EP260610b: SVOM/VT optical confirmation with blue color
  90. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  91. GRB 260515A: SOAR optical observations
  92. EP260610b: Gemini North optical counterpart candidate
  93. EP260610a: SVOM/VT optical upper limits
  94. Konus-Wind detection of GRB 260601A
  95. IPN triangulation of GRB 260601A (short/hard)
  96. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  97. EP260610a: COLIBRÍ optical upper limits
  98. Konus-Wind detection of GRB 260604C
  99. GRB 260608A: Fermi GRB Observation
  100. GRB 260604C: AstroSat CZTI detection

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