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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 trigger No 804738310: Global MASTER-Net observations report
  2. Fermi GRB 260703A: Global MASTER-Net observations report
  3. GRB 260703A: Fermi GBM Final Localization
  4. GRB 260610B: VLA detection
  5. GRB 260623A: Glowbug gamma-ray detection
  6. GRB 260614B: ATCA Radio Upper Limits
  7. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  8. Fermi trigger No 804552016: Global MASTER-Net observations report
  9. GRB 260701A: Fermi GBM Final Real-time Localization
  10. Fermi GBM trigger 804552016/260630945 is not a GRB
  11. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  12. EP260628a: EP-FXT follow-up observation
  13. GRB 260629A: Fermi GBM Final Real-time Localization
  14. Fermi GRB 260628A: Global MASTER-Net observations report
  15. EP260628a: EP-WXT detection of a fast X-ray transient
  16. GRB 260628A: Fermi GBM Final Real-time Localization
  17. The EP-WXT trigger 01709272671 is likely a flaring star
  18. EP260626a: further Liverpool Telescope optical upper limits
  19. EP260626a: EP-FXT follow-up observation
  20. EP260626a: COLIBRÍ optical upper limit
  21. EP260626a: Liverpool Telescope upper limits
  22. EP260626a: EP-WXT detection of a fast X-ray transient
  23. Konus-Wind detection of GRB 260623B / EP260623a
  24. EP260623a: TNG NIR afterglow detection
  25. GRB 260618A: Fermi GBM Observation
  26. MASS-Cube (GRID 2.0) detection of GRB 260616B
  27. EP260623a: FTW optical and NIR observations
  28. GRB 260619A: SVOM/ECLAIRs refined analysis
  29. EP260623a: Liverpool Telescope optical observations
  30. Fermi GBM trigger 804010507/260624677 is not a GRB
  31. Konus-Wind detection of GRB 260618B
  32. GRB 260624A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  33. GRB 260624A: Fermi GBM Final Real-time Localization
  34. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  35. EP260623a: WINTER J-band observations
  36. GRB 260617A: Glowbug gamma-ray detection of a short burst
  37. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  38. IPN triangulation of GRB 260605A
  39. EP260623a: Optical follow-up observations with Kinder
  40. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  41. GRB 260623A: Fermi GBM Final Real-time Localization
  42. EP260623a: SVOM/VT optical observations
  43. EP260623a: TRT optical observations
  44. EP260623a: REM optical/NIR afterglow detection
  45. EP 260623a: COLIBRÍ optical observations
  46. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  47. EP260623a: OSIRIS+/GTC redshift z = 0.703
  48. EP260623a: Las Cumbres discovery of the optical counterpart
  49. EP260623a: Einstein Probe detection of an X-ray transient
  50. GRB 260614B: EP-FXT follow-up observation
  51. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  52. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  53. EP260618a: Liverpool Telescope optical observations
  54. GRB 260619A: NOT optical observations
  55. GRB 260618B: LCO optical observations
  56. The EP-WXT trigger 01709271197 is likely a flaring star
  57. EP260618a: JinShan optical observations
  58. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  59. GRB 260618B: Fermi GBM Observation
  60. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  61. GRB 260619A: TRT optical counterpart confirmation
  62. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  63. GRB 260604B: 239Alferov CubeSat detection
  64. GRB 260604A: 239Alferov CubeSat detection
  65. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  66. GRB 260619A: SVOM/VT optical counterpart confirmation
  67. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  68. GRB 260618B: SVOM/VT optical candidate
  69. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  70. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  71. Konus-Wind detection of GRB 260617A
  72. GRB 260616B: AstroSat CZTI detection
  73. GRB 260616A: AstroSat CZTI detection
  74. GRB 260616A: SVOM/GRM observation
  75. EP260618a: OHP/T193 optical observations
  76. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  77. GRB 260619A: Kilonova-Catcher optical upper limit
  78. EP260618a: EP-FXT follow-up observation
  79. EP260618a: LCO optical counterpart confirmation
  80. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  81. EP260618a: COLIBRÍ optical counterpart candidate
  82. GRB 260616A: NuSTAR detection of prompt emission
  83. GRB 260614B: NuSTAR detection of prompt emission
  84. GRB 260619A: SVOM possible detection of a faint burst
  85. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  86. GRB 260618B: Fermi-LAT detection
  87. IPN triangulation of GRB 260617A (short)
  88. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  89. GRB 260616A: Insight-HXMT detection
  90. GRB 260618B: Fermi GBM Final Real-time Localization
  91. EP260618a: EP-WXT detection of an X-ray transient
  92. GRB 260610B: AbAO optical observations
  93. EP260616a/GRB 260616B: EP-FXT follow-up observation
  94. GRB 260506B: cubesat Avion detection
  95. GRB 260616C: GECAM-B observation of a burst
  96. GRB 260618A: Fermi GBM Final Real-time Localization
  97. GRB 260617A: Fermi GBM Detection
  98. GRB 260616A: Fermi GBM Observation
  99. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  100. GRB 260617A: Fermi GBM Final Real-time Localization

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