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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: EP/FXT follow-up observations
  2. EP260727a: Einstein Probe detection of an X-ray transient
  3. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  4. GRB 260727A: Glowbug gamma-ray detection
  5. GRB 260726A: J-band upper limit with WINTER
  6. GRB 260727A: J-band upper limit with WINTER
  7. GRB 260726A: SVOM/VT optical candidate
  8. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  9. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  10. EP260723a: SVOM/ECLAIRs Upper Limit
  11. GRB 260727A: GOTO early optical upper limit
  12. GRB 260727A: AstroSat CZTI detection
  13. GRB 260727A: Kilonova-Catcher optical upper limit
  14. GRB 260727A: LCO optical upper limits
  15. GRB 260727B: Fermi GBM Final Real-time Localization
  16. Fermi GRB 260726A: Global MASTER-Net observations report
  17. GRB 260727A: SVOM detection of a bright long burst
  18. GRB 260726A: SVOM detection of a burst
  19. GRB 260726A: Fermi GBM Final Real-time Localization
  20. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  21. EP260723a: further EP-FXT follow-up observation
  22. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  23. EP260725a: EP-WXT detection of an X-ray transient
  24. GRB 260616A: cubesat Avion detection
  25. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  26. GRB 260602B: cubesat Avion detection
  27. GRB 260601A: cubesat Avion detection
  28. EP260723a: EP-FXT follow-up observation
  29. IPN triangulation of GRB 260706B
  30. GRB 260718A: SVOM/ECLAIRs refined analysis
  31. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  32. EP260723a: SVOM/VT optical observation
  33. EP260723a: COLIBRÍ optical observations
  34. EP260723a: NOT optical conterpart confirmation
  35. EP260723a: Liverpool Telescope likely optical counterpart
  36. EP260723a: EP-WXT detection of a fast X-ray transient
  37. GRB 260723A: Fermi GBM Final Localization
  38. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  39. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  40. IceCube Alert 260722A: Global MASTER-Net observations report
  41. Konus-Wind detection of GRB 260721A
  42. GRB 260722A: Fermi GBM Final Real-time Localization
  43. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  44. Fermi GBM trigger 806384210/260722151 is not a GRB
  45. GRB 260721A: NuSTAR detection of prompt emission
  46. Konus-Wind detection of GRB 260714B
  47. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  48. GRB 260705A: Retraction of optical counterpart
  49. GRB 260714B: Insight-HXMT/HE detection
  50. GRB 260718A: EP-FXT follow-up observation
  51. Fermi trigger No 806104130: Global MASTER-Net observations report
  52. Fermi GRB 260718A: Global MASTER-Net observations report
  53. GRB 260718A: LCO optical upper limits
  54. GRB 260711A: SVOM/GRM observation
  55. GRB 260710A: SVOM/GRM observation
  56. GRB 260718A: Fermi GBM Observation
  57. GRB 260718A : GRANDMA and KNC upper limits
  58. GRB 260718A: SVOM/VT optical upper limits
  59. GRB 260718A: SVOM/VT optical upper limits from VHF data
  60. GRB 260718A: SVOM detection of a burst
  61. GRB 260714B: SVOM/GRM observation
  62. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  63. GRB 260714B: GECAM-B observation of a burst
  64. GRB 260618B: EP-FXT follow-up observation upper limit
  65. GRB 260714B: COLIBRÍ optical counterpart candidate
  66. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
  67. SVOM sb26071506: Global MASTER-Net observations report
  68. sb26071506: SVOM detection of a X-ray transient
  69. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  70. GRB 260715A: Fermi GBM Final Real-time Localization
  71. EP260703a: SVOM/ECLAIRs Upper Limit
  72. GRB 260710A: AstroSat CZTI detection
  73. GRB 260709A: AstroSat CZTI detection
  74. GRB 260714B: AstroSat CZTI detection
  75. GRB 260714B: Fermi-LAT detection
  76. GRB 260714B: Fermi GBM Detection
  77. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  78. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  79. GRB 260714B: Fermi GBM Final Real-time Localization
  80. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  81. GRB 260706A: ATCA detection of possible radio counterpart
  82. GRB 260705A: ATCA radio observations
  83. GRB 260714A: Fermi GBM Final Real-time Localization
  84. EP260713a: Einstein Probe detection of an X-ray transient
  85. GRB 260619A: SVOM/VT continuous optical observations
  86. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  87. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  88. EP260623a: KAIT optical observations
  89. EP260711a: EP-FXT follow-up observation
  90. GRB 260708A: GRANDMA Optical Observations
  91. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  92. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  93. GRB 260710A: Insight-HXMT/HE detection
  94. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  95. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  96. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  97. GRB 260708A: LCO optical observations
  98. EP260711a: Einstein Probe detection of an X-ray transient
  99. GRB 260710A: Fermi GBM Detection
  100. GRB 260709A: SVOM/GRM detection

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