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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"

35943 results found.

  1. GRB 260616A: SVOM/GRM observation
  2. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  3. GRB 260619A: Kilonova-Catcher optical upper limit
  4. EP260618a: EP-FXT follow-up observation
  5. EP260618a: LCO optical counterpart confirmation
  6. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  7. EP260618a: COLIBRÍ optical counterpart candidate
  8. GRB 260616A: NuSTAR detection of prompt emission
  9. GRB 260614B: NuSTAR detection of prompt emission
  10. GRB 260619A: SVOM possible detection of a faint burst
  11. GRB 260618B: Fermi-LAT detection
  12. IPN triangulation of GRB 260617A (short)
  13. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  14. GRB 260616A: Insight-HXMT detection
  15. GRB 260618B: Fermi GBM Final Real-time Localization
  16. EP260618a: EP-WXT detection of an X-ray transient
  17. GRB 260610B: AbAO optical observations
  18. EP260616a/GRB 260616B: EP-FXT follow-up observation
  19. GRB 260506B: cubesat Avion detection
  20. GRB 260616C: GECAM-B observation of a burst
  21. GRB 260618A: Fermi GBM Final Real-time Localization
  22. GRB 260617A: Fermi GBM Detection
  23. GRB 260616A: Fermi GBM Observation
  24. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  25. GRB 260617A: Fermi GBM Final Real-time Localization
  26. Konus-Wind detection of GRB 260616B/EP260616a
  27. Konus-Wind detection of GRB 260616A
  28. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  29. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  30. GRB 260616A: GECAM-B observation
  31. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  32. GRB 260429A: cubesat Avion detection
  33. GRB260616C: MAXI/GSC detection
  34. GRB 260616A: Fermi-LAT detection
  35. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  36. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  37. GRB 260614A: AstroSat CZTI detection
  38. EP260616a: EP-WXT detection of a fast X-ray transient
  39. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  40. GRB 260616B: Fermi GBM Detection
  41. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  42. GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
  43. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  44. GRB 260616A: Fermi GBM Final Real-time Localization
  45. GRB 260614B: SVOM/ECLAIRs refined analysis
  46. GRB 260610B: Terskol optical observations
  47. GRB 260614B: GECAM-B observation
  48. GRB 260610B: SVOM/GRM observation
  49. GRB 260614B: SVOM/VT optical afterglow confirmation
  50. GRB 260614B: Fermi GBM Observation
  51. GRB 260610B: ALMA detection
  52. GRB 260614A: GECAM-B observation
  53. GRB 260614B: SVOM/VT optical candidate from VHF data
  54. GRB 260614B: SVOM detection of a burst
  55. GRB 260614B: Fermi GBM Final Real-time Localization
  56. GRB 260611B: SVOM/GRM detection
  57. GRB 260614A: Fermi GBM Final Localization
  58. GRB 260603C: AstroSat CZTI detection
  59. GRB 260610B: further Liverpool Telescope optical observations
  60. GRB 260610B: Fermi GBM Observation
  61. GRB 260610B / AT2026owq: GRANDMA optical observations
  62. GRB 260610B / AT2026owq: further SAO RAS optical observations
  63. GRB 260610b: Liverpool Telescope optical observations
  64. GRB 260611B: CALET Gamma-Ray Burst Monitor detection
  65. GRB 260610B / AT2026owq: SVOM/VT optical observations
  66. GRB 260610B / AT2026owq: OASDG optical observations
  67. GRB 260610B: IAC-80 Optical observations
  68. GRB 260610B / AT2026owq: SAO RAS optical observations
  69. GRB 260611B: Fermi GBM Final Real-time Localization
  70. EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
  71. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  72. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  73. GRB 260610B / AT2026owq: Early ATLAS observations
  74. GRB 260610B: TRT optical observation
  75. GRB 260611A: Fermi GBM Final Real-time Localization
  76. GRB 260610B: DDOTI optical observations
  77. GRB 260610B: GOTO optical counterpart candidate
  78. GRB 260610B: Fermi GBM Final Localization
  79. GRB 260515A: SOAR optical observations
  80. Konus-Wind detection of GRB 260601A
  81. IPN triangulation of GRB 260601A (short/hard)
  82. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  83. GRB 260610A: Fermi GBM Final Real-time Localization
  84. GRB 260609A: Fermi GBM Final Localization
  85. Konus-Wind detection of GRB 260604C
  86. GRB 260608A: Fermi GRB Observation
  87. GRB 260604C: AstroSat CZTI detection
  88. IPN triangulation of GRB 260601B / EP260601a
  89. GRB 260604C: SVOM/ECLAIRs refined analysis
  90. GRB 260608A: SVOM/ECLAIRs refined analysis
  91. Konus-Wind detection of GRB 260607B
  92. GRB 260607B: GECAM-B observation
  93. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  94. GRB 260608C: Fermi GBM Final Real-time Localization
  95. GRB 260604C: further SAO RAS optical observations
  96. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  97. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  98. GRB 260608B: Fermi GBM Final Localization
  99. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  100. GRB 260604C: SVOM/C-GFT upper limit

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