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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"

36154 results found.

  1. GRB 260614B: ATCA Radio Upper Limits
  2. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  3. GRB 260701A: Fermi GBM Final Real-time Localization
  4. Fermi GBM trigger 804552016/260630945 is not a GRB
  5. GRB 260629A: Fermi GBM Final Real-time Localization
  6. Fermi GRB 260628A: Global MASTER-Net observations report
  7. GRB 260628A: Fermi GBM Final Real-time Localization
  8. Konus-Wind detection of GRB 260623B / EP260623a
  9. GRB 260618A: Fermi GBM Observation
  10. MASS-Cube (GRID 2.0) detection of GRB 260616B
  11. GRB 260619A: SVOM/ECLAIRs refined analysis
  12. Fermi GBM trigger 804010507/260624677 is not a GRB
  13. Konus-Wind detection of GRB 260618B
  14. GRB 260624A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  15. GRB 260624A: Fermi GBM Final Real-time Localization
  16. GRB 260617A: Glowbug gamma-ray detection of a short burst
  17. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  18. IPN triangulation of GRB 260605A
  19. GRB 260623A: Fermi GBM Final Real-time Localization
  20. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  21. GRB 260614B: EP-FXT follow-up observation
  22. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  23. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  24. GRB 260619A: NOT optical observations
  25. GRB 260618B: LCO optical observations
  26. EP260618a: JinShan optical observations
  27. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  28. GRB 260618B: Fermi GBM Observation
  29. GRB 260619A: TRT optical counterpart confirmation
  30. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  31. GRB 260604B: 239Alferov CubeSat detection
  32. GRB 260604A: 239Alferov CubeSat detection
  33. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  34. GRB 260619A: SVOM/VT optical counterpart confirmation
  35. GRB 260618B: SVOM/VT optical candidate
  36. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  37. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  38. Konus-Wind detection of GRB 260617A
  39. GRB 260616B: AstroSat CZTI detection
  40. GRB 260616A: AstroSat CZTI detection
  41. GRB 260616A: SVOM/GRM observation
  42. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  43. GRB 260619A: Kilonova-Catcher optical upper limit
  44. EP260618a: EP-FXT follow-up observation
  45. EP260618a: LCO optical counterpart confirmation
  46. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  47. EP260618a: COLIBRÍ optical counterpart candidate
  48. GRB 260616A: NuSTAR detection of prompt emission
  49. GRB 260614B: NuSTAR detection of prompt emission
  50. GRB 260619A: SVOM possible detection of a faint burst
  51. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  52. GRB 260618B: Fermi-LAT detection
  53. IPN triangulation of GRB 260617A (short)
  54. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  55. GRB 260616A: Insight-HXMT detection
  56. GRB 260618B: Fermi GBM Final Real-time Localization
  57. EP260618a: EP-WXT detection of an X-ray transient
  58. GRB 260610B: AbAO optical observations
  59. EP260616a/GRB 260616B: EP-FXT follow-up observation
  60. GRB 260506B: cubesat Avion detection
  61. GRB 260616C: GECAM-B observation of a burst
  62. GRB 260618A: Fermi GBM Final Real-time Localization
  63. GRB 260617A: Fermi GBM Detection
  64. GRB 260616A: Fermi GBM Observation
  65. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  66. GRB 260617A: Fermi GBM Final Real-time Localization
  67. Konus-Wind detection of GRB 260616B/EP260616a
  68. Konus-Wind detection of GRB 260616A
  69. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  70. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  71. GRB 260616A: GECAM-B observation
  72. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  73. GRB 260429A: cubesat Avion detection
  74. GRB260616C: MAXI/GSC detection
  75. GRB 260616A: Fermi-LAT detection
  76. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  77. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  78. GRB 260614A: AstroSat CZTI detection
  79. EP260616a: EP-WXT detection of a fast X-ray transient
  80. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  81. GRB 260616B: Fermi GBM Detection
  82. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  83. GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
  84. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  85. GRB 260616A: Fermi GBM Final Real-time Localization
  86. GRB 260614B: SVOM/ECLAIRs refined analysis
  87. GRB 260610B: Terskol optical observations
  88. GRB 260614B: GECAM-B observation
  89. GRB 260610B: SVOM/GRM observation
  90. GRB 260614B: SVOM/VT optical afterglow confirmation
  91. GRB 260614B: Fermi GBM Observation
  92. GRB 260610B: ALMA detection
  93. GRB 260614A: GECAM-B observation
  94. GRB 260614B: SVOM/VT optical candidate from VHF data
  95. GRB 260614B: SVOM detection of a burst
  96. GRB 260614B: Fermi GBM Final Real-time Localization
  97. GRB 260611B: SVOM/GRM detection
  98. GRB 260614A: Fermi GBM Final Localization
  99. GRB 260603C: AstroSat CZTI detection
  100. GRB 260610B: further Liverpool Telescope optical observations

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