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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 260727A: AstroSat CZTI detection
  2. GRB 260727A: Kilonova-Catcher optical upper limit
  3. GRB 260727A: LCO optical upper limits
  4. GRB 260727B: Fermi GBM Final Real-time Localization
  5. Fermi GRB 260726A: Global MASTER-Net observations report
  6. GRB 260727A: SVOM detection of a bright long burst
  7. GRB 260726A: SVOM detection of a burst
  8. GRB 260726A: Fermi GBM Final Real-time Localization
  9. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  10. EP260723a: further EP-FXT follow-up observation
  11. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  12. EP260725a: EP-WXT detection of an X-ray transient
  13. GRB 260616A: cubesat Avion detection
  14. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  15. GRB 260602B: cubesat Avion detection
  16. GRB 260601A: cubesat Avion detection
  17. EP260723a: EP-FXT follow-up observation
  18. IPN triangulation of GRB 260706B
  19. GRB 260718A: SVOM/ECLAIRs refined analysis
  20. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  21. EP260723a: SVOM/VT optical observation
  22. EP260723a: COLIBRÍ optical observations
  23. EP260723a: NOT optical conterpart confirmation
  24. EP260723a: Liverpool Telescope likely optical counterpart
  25. EP260723a: EP-WXT detection of a fast X-ray transient
  26. GRB 260723A: Fermi GBM Final Localization
  27. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  28. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  29. IceCube Alert 260722A: Global MASTER-Net observations report
  30. Konus-Wind detection of GRB 260721A
  31. GRB 260722A: Fermi GBM Final Real-time Localization
  32. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  33. Fermi GBM trigger 806384210/260722151 is not a GRB
  34. GRB 260721A: NuSTAR detection of prompt emission
  35. Konus-Wind detection of GRB 260714B
  36. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  37. GRB 260705A: Retraction of optical counterpart
  38. GRB 260714B: Insight-HXMT/HE detection
  39. GRB 260718A: EP-FXT follow-up observation
  40. Fermi trigger No 806104130: Global MASTER-Net observations report
  41. Fermi GRB 260718A: Global MASTER-Net observations report
  42. GRB 260718A: LCO optical upper limits
  43. GRB 260711A: SVOM/GRM observation
  44. GRB 260710A: SVOM/GRM observation
  45. GRB 260718A: Fermi GBM Observation
  46. GRB 260718A : GRANDMA and KNC upper limits
  47. GRB 260718A: SVOM/VT optical upper limits
  48. GRB 260718A: SVOM/VT optical upper limits from VHF data
  49. GRB 260718A: SVOM detection of a burst
  50. GRB 260714B: SVOM/GRM observation
  51. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  52. GRB 260714B: GECAM-B observation of a burst
  53. GRB 260618B: EP-FXT follow-up observation upper limit
  54. GRB 260714B: COLIBRÍ optical counterpart candidate
  55. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
  56. SVOM sb26071506: Global MASTER-Net observations report
  57. sb26071506: SVOM detection of a X-ray transient
  58. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  59. GRB 260715A: Fermi GBM Final Real-time Localization
  60. EP260703a: SVOM/ECLAIRs Upper Limit
  61. GRB 260710A: AstroSat CZTI detection
  62. GRB 260709A: AstroSat CZTI detection
  63. GRB 260714B: AstroSat CZTI detection
  64. GRB 260714B: Fermi-LAT detection
  65. GRB 260714B: Fermi GBM Detection
  66. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  67. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  68. GRB 260714B: Fermi GBM Final Real-time Localization
  69. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  70. GRB 260706A: ATCA detection of possible radio counterpart
  71. GRB 260705A: ATCA radio observations
  72. GRB 260714A: Fermi GBM Final Real-time Localization
  73. EP260713a: Einstein Probe detection of an X-ray transient
  74. GRB 260619A: SVOM/VT continuous optical observations
  75. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  76. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  77. EP260623a: KAIT optical observations
  78. EP260711a: EP-FXT follow-up observation
  79. GRB 260708A: GRANDMA Optical Observations
  80. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  81. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  82. GRB 260710A: Insight-HXMT/HE detection
  83. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  84. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  85. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  86. GRB 260708A: LCO optical observations
  87. EP260711a: Einstein Probe detection of an X-ray transient
  88. GRB 260710A: Fermi GBM Detection
  89. GRB 260709A: SVOM/GRM detection
  90. GRB 260709A: GECAM-B observation
  91. The EP-WXT trigger 01709274666 is likely a new outburst of the CV SS Cyg
  92. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  93. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  94. GRB 260705C: AstroSat CZTI detection
  95. GRB 260710A: Fermi GBM Final Real-time Localization
  96. GRB 260708A: Glowbug gamma-ray detection
  97. GRB 260704A: SVOM/ECLAIRs refined analysis
  98. GRB 260706A : GRANDMA Upper limits
  99. GRB 260708A: Kilonova-Catcher optical afterglow detection
  100. GRB 260708A: GECAM-B observation of a burst

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