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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"

42746 results found.

  1. Konus-Wind detection of GRB 260618B
  2. GRB 260624A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  3. GRB 260624A: Fermi GBM Final Real-time Localization
  4. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  5. EP260623a: WINTER J-band observations
  6. GRB 260617A: Glowbug gamma-ray detection of a short burst
  7. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  8. IPN triangulation of GRB 260605A
  9. EP260623a: Optical follow-up observations with Kinder
  10. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  11. GRB 260623A: Fermi GBM Final Real-time Localization
  12. EP260623a: SVOM/VT optical observations
  13. EP260623a: TRT optical observations
  14. EP260623a: REM optical/NIR afterglow detection
  15. EP 260623a: COLIBRÍ optical observations
  16. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  17. EP260623a: OSIRIS+/GTC redshift z = 0.703
  18. EP260623a: Las Cumbres discovery of the optical counterpart
  19. EP260623a: Einstein Probe detection of an X-ray transient
  20. GRB 260614B: EP-FXT follow-up observation
  21. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  22. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  23. EP260618a: Liverpool Telescope optical observations
  24. GRB 260619A: NOT optical observations
  25. GRB 260618B: LCO optical observations
  26. The EP-WXT trigger 01709271197 is likely a flaring star
  27. EP260618a: JinShan optical observations
  28. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  29. GRB 260618B: Fermi GBM Observation
  30. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  31. GRB 260619A: TRT optical counterpart confirmation
  32. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  33. GRB 260604B: 239Alferov CubeSat detection
  34. GRB 260604A: 239Alferov CubeSat detection
  35. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  36. GRB 260619A: SVOM/VT optical counterpart confirmation
  37. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  38. GRB 260618B: SVOM/VT optical candidate
  39. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  40. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  41. Konus-Wind detection of GRB 260617A
  42. GRB 260616B: AstroSat CZTI detection
  43. GRB 260616A: AstroSat CZTI detection
  44. GRB 260616A: SVOM/GRM observation
  45. EP260618a: OHP/T193 optical observations
  46. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  47. GRB 260619A: Kilonova-Catcher optical upper limit
  48. EP260618a: EP-FXT follow-up observation
  49. EP260618a: LCO optical counterpart confirmation
  50. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  51. EP260618a: COLIBRÍ optical counterpart candidate
  52. GRB 260616A: NuSTAR detection of prompt emission
  53. GRB 260614B: NuSTAR detection of prompt emission
  54. GRB 260619A: SVOM possible detection of a faint burst
  55. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  56. GRB 260618B: Fermi-LAT detection
  57. IPN triangulation of GRB 260617A (short)
  58. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  59. GRB 260616A: Insight-HXMT detection
  60. GRB 260618B: Fermi GBM Final Real-time Localization
  61. EP260618a: EP-WXT detection of an X-ray transient
  62. GRB 260610B: AbAO optical observations
  63. EP260616a/GRB 260616B: EP-FXT follow-up observation
  64. GRB 260506B: cubesat Avion detection
  65. GRB 260616C: GECAM-B observation of a burst
  66. GRB 260618A: Fermi GBM Final Real-time Localization
  67. GRB 260617A: Fermi GBM Detection
  68. GRB 260616A: Fermi GBM Observation
  69. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  70. GRB 260617A: Fermi GBM Final Real-time Localization
  71. Konus-Wind detection of GRB 260616B/EP260616a
  72. Konus-Wind detection of GRB 260616A
  73. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  74. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  75. GRB 260616A: GECAM-B observation
  76. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  77. GRB260616C: MAXI/GSC detection
  78. GRB 260616A: Fermi-LAT detection
  79. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  80. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  81. GRB 260614A: AstroSat CZTI detection
  82. EP260616a: EP-WXT detection of a fast X-ray transient
  83. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  84. The EP-WXT trigger 01709270148 is likely a flaring star
  85. GRB 260616B: Fermi GBM Detection
  86. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  87. GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
  88. The EP-WXT trigger 01709269893 is likely a flaring star
  89. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  90. GRB 260616A: Fermi GBM Final Real-time Localization
  91. GRB 260614B: SVOM/ECLAIRs refined analysis
  92. GRB 260610B: Terskol optical observations
  93. GRB 260614B: GECAM-B observation
  94. GRB 260610B: SVOM/GRM observation
  95. GRB 260614B: SVOM/VT optical afterglow confirmation
  96. GRB 260614B: Fermi GBM Observation
  97. GRB 260610B: ALMA detection
  98. GRB 260614A: GECAM-B observation
  99. GRB 260614B: SVOM/VT optical candidate from VHF data
  100. GRB 260614B: SVOM detection of a burst

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