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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"

37946 results found.

  1. GRB 260705C: Fermi GBM Final Localization
  2. GRB 260705B: Fermi GBM Final Real-time Localization
  3. Fermi GBM Sub-Threshold Detection of GRB 260705A
  4. GRB 260705A: SVOM detection of a burst
  5. GRB 260704A: EP-FXT follow-up observation
  6. GRB 260629A: SVOM/GRM observation of a short burst
  7. GRB 260629A: GECAM-A observation of a short burst
  8. GRB 260629A: AstroSat CZTI detection
  9. GRB 260704A: SVOM detection of a possible GRB
  10. GRB 260703B: Fermi GBM Final Localization
  11. Fermi trigger No 804738310: Global MASTER-Net observations report
  12. Fermi GRB 260703A: Global MASTER-Net observations report
  13. GRB 260703A: Fermi GBM Final Localization
  14. GRB 260610B: VLA detection
  15. GRB 260623A: Glowbug gamma-ray detection
  16. GRB 260614B: ATCA Radio Upper Limits
  17. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  18. Fermi trigger No 804552016: Global MASTER-Net observations report
  19. GRB 260701A: Fermi GBM Final Real-time Localization
  20. Fermi GBM trigger 804552016/260630945 is not a GRB
  21. GRB 260629A: Fermi GBM Final Real-time Localization
  22. Fermi GRB 260628A: Global MASTER-Net observations report
  23. GRB 260628A: Fermi GBM Final Real-time Localization
  24. Konus-Wind detection of GRB 260623B / EP260623a
  25. GRB 260618A: Fermi GBM Observation
  26. MASS-Cube (GRID 2.0) detection of GRB 260616B
  27. GRB 260619A: SVOM/ECLAIRs refined analysis
  28. Fermi GBM trigger 804010507/260624677 is not a GRB
  29. Konus-Wind detection of GRB 260618B
  30. GRB 260624A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  31. GRB 260624A: Fermi GBM Final Real-time Localization
  32. GRB 260617A: Glowbug gamma-ray detection of a short burst
  33. IPN triangulation of GRB 260605A
  34. GRB 260623A: Fermi GBM Final Real-time Localization
  35. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  36. GRB 260614B: EP-FXT follow-up observation
  37. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  38. GRB 260619A: NOT optical observations
  39. GRB 260618B: LCO optical observations
  40. EP260618a: JinShan optical observations
  41. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  42. GRB 260618B: Fermi GBM Observation
  43. GRB 260619A: TRT optical counterpart confirmation
  44. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  45. GRB 260604B: 239Alferov CubeSat detection
  46. GRB 260604A: 239Alferov CubeSat detection
  47. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  48. GRB 260619A: SVOM/VT optical counterpart confirmation
  49. GRB 260618B: SVOM/VT optical candidate
  50. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  51. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  52. Konus-Wind detection of GRB 260617A
  53. GRB 260616B: AstroSat CZTI detection
  54. GRB 260616A: AstroSat CZTI detection
  55. GRB 260616A: SVOM/GRM observation
  56. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  57. GRB 260619A: Kilonova-Catcher optical upper limit
  58. EP260618a: EP-FXT follow-up observation
  59. EP260618a: LCO optical counterpart confirmation
  60. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  61. EP260618a: COLIBRÍ optical counterpart candidate
  62. GRB 260616A: NuSTAR detection of prompt emission
  63. GRB 260614B: NuSTAR detection of prompt emission
  64. GRB 260619A: SVOM possible detection of a faint burst
  65. GRB 260618B: Fermi-LAT detection
  66. IPN triangulation of GRB 260617A (short)
  67. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  68. GRB 260616A: Insight-HXMT detection
  69. GRB 260618B: Fermi GBM Final Real-time Localization
  70. EP260618a: EP-WXT detection of an X-ray transient
  71. GRB 260610B: AbAO optical observations
  72. EP260616a/GRB 260616B: EP-FXT follow-up observation
  73. GRB 260506B: cubesat Avion detection
  74. GRB 260616C: GECAM-B observation of a burst
  75. GRB 260618A: Fermi GBM Final Real-time Localization
  76. GRB 260617A: Fermi GBM Detection
  77. GRB 260616A: Fermi GBM Observation
  78. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  79. GRB 260617A: Fermi GBM Final Real-time Localization
  80. Konus-Wind detection of GRB 260616B/EP260616a
  81. Konus-Wind detection of GRB 260616A
  82. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  83. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  84. GRB 260616A: GECAM-B observation
  85. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  86. GRB 260429A: cubesat Avion detection
  87. GRB260616C: MAXI/GSC detection
  88. GRB 260616A: Fermi-LAT detection
  89. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  90. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  91. GRB 260614A: AstroSat CZTI detection
  92. EP260616a: EP-WXT detection of a fast X-ray transient
  93. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  94. GRB 260616B: Fermi GBM Detection
  95. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  96. GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
  97. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  98. GRB 260616A: Fermi GBM Final Real-time Localization
  99. GRB 260614B: SVOM/ECLAIRs refined analysis
  100. GRB 260610B: Terskol optical observations

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