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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 260704A: SVOM detection of a possible GRB
  2. GRB 260703B: Fermi GBM Final Localization
  3. EP260703a: EP-WXT detection of a fast X-ray transient
  4. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  5. Fermi trigger No 804738310: Global MASTER-Net observations report
  6. Fermi GRB 260703A: Global MASTER-Net observations report
  7. GRB 260703A: Fermi GBM Final Localization
  8. GRB 260610B: VLA detection
  9. GRB 260623A: Glowbug gamma-ray detection
  10. GRB 260614B: ATCA Radio Upper Limits
  11. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  12. Fermi trigger No 804552016: Global MASTER-Net observations report
  13. GRB 260701A: Fermi GBM Final Real-time Localization
  14. Fermi GBM trigger 804552016/260630945 is not a GRB
  15. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  16. EP260628a: EP-FXT follow-up observation
  17. GRB 260629A: Fermi GBM Final Real-time Localization
  18. Fermi GRB 260628A: Global MASTER-Net observations report
  19. EP260628a: EP-WXT detection of a fast X-ray transient
  20. GRB 260628A: Fermi GBM Final Real-time Localization
  21. The EP-WXT trigger 01709272671 is likely a flaring star
  22. EP260626a: further Liverpool Telescope optical upper limits
  23. EP260626a: EP-FXT follow-up observation
  24. EP260626a: COLIBRÍ optical upper limit
  25. EP260626a: Liverpool Telescope upper limits
  26. EP260626a: EP-WXT detection of a fast X-ray transient
  27. Konus-Wind detection of GRB 260623B / EP260623a
  28. EP260623a: TNG NIR afterglow detection
  29. GRB 260618A: Fermi GBM Observation
  30. MASS-Cube (GRID 2.0) detection of GRB 260616B
  31. EP260623a: FTW optical and NIR observations
  32. GRB 260619A: SVOM/ECLAIRs refined analysis
  33. EP260623a: Liverpool Telescope optical observations
  34. Fermi GBM trigger 804010507/260624677 is not a GRB
  35. Konus-Wind detection of GRB 260618B
  36. GRB 260624A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  37. GRB 260624A: Fermi GBM Final Real-time Localization
  38. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  39. EP260623a: WINTER J-band observations
  40. GRB 260617A: Glowbug gamma-ray detection of a short burst
  41. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  42. IPN triangulation of GRB 260605A
  43. EP260623a: Optical follow-up observations with Kinder
  44. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  45. GRB 260623A: Fermi GBM Final Real-time Localization
  46. EP260623a: SVOM/VT optical observations
  47. EP260623a: TRT optical observations
  48. EP260623a: REM optical/NIR afterglow detection
  49. EP 260623a: COLIBRÍ optical observations
  50. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  51. EP260623a: OSIRIS+/GTC redshift z = 0.703
  52. EP260623a: Las Cumbres discovery of the optical counterpart
  53. EP260623a: Einstein Probe detection of an X-ray transient
  54. GRB 260614B: EP-FXT follow-up observation
  55. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  56. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  57. EP260618a: Liverpool Telescope optical observations
  58. GRB 260619A: NOT optical observations
  59. GRB 260618B: LCO optical observations
  60. The EP-WXT trigger 01709271197 is likely a flaring star
  61. EP260618a: JinShan optical observations
  62. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  63. GRB 260618B: Fermi GBM Observation
  64. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  65. GRB 260619A: TRT optical counterpart confirmation
  66. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  67. GRB 260604B: 239Alferov CubeSat detection
  68. GRB 260604A: 239Alferov CubeSat detection
  69. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  70. GRB 260619A: SVOM/VT optical counterpart confirmation
  71. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  72. GRB 260618B: SVOM/VT optical candidate
  73. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  74. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  75. Konus-Wind detection of GRB 260617A
  76. GRB 260616B: AstroSat CZTI detection
  77. GRB 260616A: AstroSat CZTI detection
  78. GRB 260616A: SVOM/GRM observation
  79. EP260618a: OHP/T193 optical observations
  80. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  81. GRB 260619A: Kilonova-Catcher optical upper limit
  82. EP260618a: EP-FXT follow-up observation
  83. EP260618a: LCO optical counterpart confirmation
  84. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  85. EP260618a: COLIBRÍ optical counterpart candidate
  86. GRB 260616A: NuSTAR detection of prompt emission
  87. GRB 260614B: NuSTAR detection of prompt emission
  88. GRB 260619A: SVOM possible detection of a faint burst
  89. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  90. GRB 260618B: Fermi-LAT detection
  91. IPN triangulation of GRB 260617A (short)
  92. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  93. GRB 260616A: Insight-HXMT detection
  94. GRB 260618B: Fermi GBM Final Real-time Localization
  95. EP260618a: EP-WXT detection of an X-ray transient
  96. GRB 260610B: AbAO optical observations
  97. EP260616a/GRB 260616B: EP-FXT follow-up observation
  98. GRB 260506B: cubesat Avion detection
  99. GRB 260616C: GECAM-B observation of a burst
  100. GRB 260618A: Fermi GBM Final Real-time Localization

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