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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 260614B: ATCA Radio Upper Limits
  2. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  3. Fermi trigger No 804552016: Global MASTER-Net observations report
  4. GRB 260701A: Fermi GBM Final Real-time Localization
  5. Fermi GBM trigger 804552016/260630945 is not a GRB
  6. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  7. EP260628a: EP-FXT follow-up observation
  8. GRB 260629A: Fermi GBM Final Real-time Localization
  9. Fermi GRB 260628A: Global MASTER-Net observations report
  10. EP260628a: EP-WXT detection of a fast X-ray transient
  11. GRB 260628A: Fermi GBM Final Real-time Localization
  12. The EP-WXT trigger 01709272671 is likely a flaring star
  13. EP260626a: further Liverpool Telescope optical upper limits
  14. EP260626a: EP-FXT follow-up observation
  15. EP260626a: COLIBRÍ optical upper limit
  16. EP260626a: Liverpool Telescope upper limits
  17. EP260626a: EP-WXT detection of a fast X-ray transient
  18. Konus-Wind detection of GRB 260623B / EP260623a
  19. EP260623a: TNG NIR afterglow detection
  20. GRB 260618A: Fermi GBM Observation
  21. MASS-Cube (GRID 2.0) detection of GRB 260616B
  22. EP260623a: FTW optical and NIR observations
  23. GRB 260619A: SVOM/ECLAIRs refined analysis
  24. EP260623a: Liverpool Telescope optical observations
  25. Fermi GBM trigger 804010507/260624677 is not a GRB
  26. Konus-Wind detection of GRB 260618B
  27. GRB 260624A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  28. GRB 260624A: Fermi GBM Final Real-time Localization
  29. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  30. EP260623a: WINTER J-band observations
  31. GRB 260617A: Glowbug gamma-ray detection of a short burst
  32. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  33. IPN triangulation of GRB 260605A
  34. EP260623a: Optical follow-up observations with Kinder
  35. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  36. GRB 260623A: Fermi GBM Final Real-time Localization
  37. EP260623a: SVOM/VT optical observations
  38. EP260623a: TRT optical observations
  39. EP260623a: REM optical/NIR afterglow detection
  40. EP 260623a: COLIBRÍ optical observations
  41. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  42. EP260623a: OSIRIS+/GTC redshift z = 0.703
  43. EP260623a: Las Cumbres discovery of the optical counterpart
  44. EP260623a: Einstein Probe detection of an X-ray transient
  45. GRB 260614B: EP-FXT follow-up observation
  46. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  47. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  48. EP260618a: Liverpool Telescope optical observations
  49. GRB 260619A: NOT optical observations
  50. GRB 260618B: LCO optical observations
  51. The EP-WXT trigger 01709271197 is likely a flaring star
  52. EP260618a: JinShan optical observations
  53. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  54. GRB 260618B: Fermi GBM Observation
  55. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  56. GRB 260619A: TRT optical counterpart confirmation
  57. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  58. GRB 260604B: 239Alferov CubeSat detection
  59. GRB 260604A: 239Alferov CubeSat detection
  60. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  61. GRB 260619A: SVOM/VT optical counterpart confirmation
  62. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  63. GRB 260618B: SVOM/VT optical candidate
  64. GRB 260618B: SVOM/VT optical candidate
  65. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  66. Konus-Wind detection of GRB 260617A
  67. GRB 260616B: AstroSat CZTI detection
  68. GRB 260616A: AstroSat CZTI detection
  69. GRB 260616A: SVOM/GRM observation
  70. EP260618a: OHP/T193 optical observations
  71. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  72. GRB 260619A: Kilonova-Catcher optical upper limit
  73. EP260618a: EP-FXT follow-up observation
  74. EP260618a: LCO optical counterpart confirmation
  75. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  76. EP260618a: COLIBRÍ optical counterpart candidate
  77. GRB 260616A: NuSTAR detection of prompt emission
  78. GRB 260614B: NuSTAR detection of prompt emission
  79. GRB 260619A: SVOM possible detection of a faint burst
  80. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  81. GRB 260618B: Fermi-LAT detection
  82. IPN triangulation of GRB 260617A (short)
  83. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  84. GRB 260616A: Insight-HXMT detection
  85. GRB 260618B: Fermi GBM Final Real-time Localization
  86. EP260618a: EP-WXT detection of an X-ray transient
  87. GRB 260610B: AbAO optical observations
  88. EP260616a/GRB 260616B: EP-FXT follow-up observation
  89. GRB 260506B: cubesat Avion detection
  90. GRB 260616C: GECAM-B observation of a burst
  91. GRB 260618A: Fermi GBM Final Real-time Localization
  92. GRB 260617A: Fermi GBM Detection
  93. GRB 260616A: Fermi GBM Observation
  94. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  95. GRB 260617A: Fermi GBM Final Real-time Localization
  96. Konus-Wind detection of GRB 260616B/EP260616a
  97. Konus-Wind detection of GRB 260616A
  98. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  99. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  100. GRB 260616A: GECAM-B observation

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