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

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