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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. Fermi GRB 260703A: Global MASTER-Net observations report
  2. GRB 260703A: Fermi GBM Final Localization
  3. GRB 260610B: VLA detection
  4. GRB 260623A: Glowbug gamma-ray detection
  5. GRB 260614B: ATCA Radio Upper Limits
  6. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  7. Fermi trigger No 804552016: Global MASTER-Net observations report
  8. GRB 260701A: Fermi GBM Final Real-time Localization
  9. Fermi GBM trigger 804552016/260630945 is not a GRB
  10. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  11. EP260628a: EP-FXT follow-up observation
  12. GRB 260629A: Fermi GBM Final Real-time Localization
  13. Fermi GRB 260628A: Global MASTER-Net observations report
  14. EP260628a: EP-WXT detection of a fast X-ray transient
  15. GRB 260628A: Fermi GBM Final Real-time Localization
  16. The EP-WXT trigger 01709272671 is likely a flaring star
  17. EP260626a: further Liverpool Telescope optical upper limits
  18. EP260626a: EP-FXT follow-up observation
  19. EP260626a: COLIBRÍ optical upper limit
  20. EP260626a: Liverpool Telescope upper limits
  21. EP260626a: EP-WXT detection of a fast X-ray transient
  22. Konus-Wind detection of GRB 260623B / EP260623a
  23. EP260623a: TNG NIR afterglow detection
  24. GRB 260618A: Fermi GBM Observation
  25. MASS-Cube (GRID 2.0) detection of GRB 260616B
  26. EP260623a: FTW optical and NIR observations
  27. GRB 260619A: SVOM/ECLAIRs refined analysis
  28. EP260623a: Liverpool Telescope optical observations
  29. Fermi GBM trigger 804010507/260624677 is not a GRB
  30. Konus-Wind detection of GRB 260618B
  31. GRB 260624A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  32. GRB 260624A: Fermi GBM Final Real-time Localization
  33. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  34. EP260623a: WINTER J-band observations
  35. GRB 260617A: Glowbug gamma-ray detection of a short burst
  36. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  37. IPN triangulation of GRB 260605A
  38. EP260623a: Optical follow-up observations with Kinder
  39. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  40. GRB 260623A: Fermi GBM Final Real-time Localization
  41. EP260623a: SVOM/VT optical observations
  42. EP260623a: TRT optical observations
  43. EP260623a: REM optical/NIR afterglow detection
  44. EP 260623a: COLIBRÍ optical observations
  45. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  46. EP260623a: OSIRIS+/GTC redshift z = 0.703
  47. EP260623a: Las Cumbres discovery of the optical counterpart
  48. EP260623a: Einstein Probe detection of an X-ray transient
  49. GRB 260614B: EP-FXT follow-up observation
  50. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  51. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  52. EP260618a: Liverpool Telescope optical observations
  53. GRB 260619A: NOT optical observations
  54. GRB 260618B: LCO optical observations
  55. The EP-WXT trigger 01709271197 is likely a flaring star
  56. EP260618a: JinShan optical observations
  57. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  58. GRB 260618B: Fermi GBM Observation
  59. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  60. GRB 260619A: TRT optical counterpart confirmation
  61. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  62. GRB 260604B: 239Alferov CubeSat detection
  63. GRB 260604A: 239Alferov CubeSat detection
  64. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  65. GRB 260619A: SVOM/VT optical counterpart confirmation
  66. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  67. GRB 260618B: SVOM/VT optical candidate
  68. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  69. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  70. Konus-Wind detection of GRB 260617A
  71. GRB 260616B: AstroSat CZTI detection
  72. GRB 260616A: AstroSat CZTI detection
  73. GRB 260616A: SVOM/GRM observation
  74. EP260618a: OHP/T193 optical observations
  75. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  76. GRB 260619A: Kilonova-Catcher optical upper limit
  77. EP260618a: EP-FXT follow-up observation
  78. EP260618a: LCO optical counterpart confirmation
  79. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  80. EP260618a: COLIBRÍ optical counterpart candidate
  81. GRB 260616A: NuSTAR detection of prompt emission
  82. GRB 260614B: NuSTAR detection of prompt emission
  83. GRB 260619A: SVOM possible detection of a faint burst
  84. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  85. GRB 260618B: Fermi-LAT detection
  86. IPN triangulation of GRB 260617A (short)
  87. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  88. GRB 260616A: Insight-HXMT detection
  89. GRB 260618B: Fermi GBM Final Real-time Localization
  90. EP260618a: EP-WXT detection of an X-ray transient
  91. GRB 260610B: AbAO optical observations
  92. EP260616a/GRB 260616B: EP-FXT follow-up observation
  93. GRB 260506B: cubesat Avion detection
  94. GRB 260616C: GECAM-B observation of a burst
  95. GRB 260618A: Fermi GBM Final Real-time Localization
  96. GRB 260617A: Fermi GBM Detection
  97. GRB 260616A: Fermi GBM Observation
  98. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  99. GRB 260617A: Fermi GBM Final Real-time Localization
  100. Konus-Wind detection of GRB 260616B/EP260616a

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