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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: AbAO and SAO RAS optical observations
  2. EP260728a: EP-FXT follow-up observation
  3. GRB 260726A: EP-FXT follow-up observations
  4. EP260728a: Einstein Probe detection of a fast X-ray transient
  5. GRB 260727A: SVOM/GRM observation
  6. GRB 260726A: Fermi GBM Observation
  7. EP260727a: 1.5m OSN optical counterpart detection
  8. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  9. EP260727a: OHP/T193 optical observations
  10. Konus-Wind detection of GRB 260727A
  11. GRB 260726A: Liverpool Telescope optical observations
  12. GRB 260727A: Liverpool Telescope optical upper limits
  13. EP260727a: Liverpool Telescope confirmation of optical counterpart
  14. EP260727a: NUTTELA-TAO Early Optical Limits
  15. GRB 260728A: Fermi GBM Final Localization
  16. GRB 260727A: EP/FXT follow-up observations
  17. EP260727a: Einstein Probe detection of an X-ray transient
  18. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  19. GRB 260727A: Glowbug gamma-ray detection
  20. GRB 260726A: J-band upper limit with WINTER
  21. GRB 260727A: J-band upper limit with WINTER
  22. GRB 260726A: SVOM/VT optical candidate
  23. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  24. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  25. EP260723a: SVOM/ECLAIRs Upper Limit
  26. GRB 260727A: GOTO early optical upper limit
  27. GRB 260727A: AstroSat CZTI detection
  28. GRB 260727A: Kilonova-Catcher optical upper limit
  29. GRB 260727A: LCO optical upper limits
  30. GRB 260727B: Fermi GBM Final Real-time Localization
  31. Fermi GRB 260726A: Global MASTER-Net observations report
  32. GRB 260727A: SVOM detection of a bright long burst
  33. GRB 260726A: SVOM detection of a burst
  34. GRB 260726A: Fermi GBM Final Real-time Localization
  35. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  36. EP260723a: further EP-FXT follow-up observation
  37. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  38. EP260725a: EP-WXT detection of an X-ray transient
  39. GRB 260616A: cubesat Avion detection
  40. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  41. GRB 260602B: cubesat Avion detection
  42. GRB 260601A: cubesat Avion detection
  43. EP260723a: EP-FXT follow-up observation
  44. IPN triangulation of GRB 260706B
  45. GRB 260718A: SVOM/ECLAIRs refined analysis
  46. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  47. EP260723a: SVOM/VT optical observation
  48. EP260723a: COLIBRÍ optical observations
  49. EP260723a: NOT optical conterpart confirmation
  50. EP260723a: Liverpool Telescope likely optical counterpart
  51. EP260723a: EP-WXT detection of a fast X-ray transient
  52. GRB 260723A: Fermi GBM Final Localization
  53. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  54. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  55. IceCube Alert 260722A: Global MASTER-Net observations report
  56. Konus-Wind detection of GRB 260721A
  57. GRB 260722A: Fermi GBM Final Real-time Localization
  58. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  59. Fermi GBM trigger 806384210/260722151 is not a GRB
  60. GRB 260721A: NuSTAR detection of prompt emission
  61. Konus-Wind detection of GRB 260714B
  62. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  63. GRB 260705A: Retraction of optical counterpart
  64. GRB 260714B: Insight-HXMT/HE detection
  65. GRB 260718A: EP-FXT follow-up observation
  66. Fermi trigger No 806104130: Global MASTER-Net observations report
  67. Fermi GRB 260718A: Global MASTER-Net observations report
  68. GRB 260718A: LCO optical upper limits
  69. GRB 260711A: SVOM/GRM observation
  70. GRB 260710A: SVOM/GRM observation
  71. GRB 260718A: Fermi GBM Observation
  72. GRB 260718A : GRANDMA and KNC upper limits
  73. GRB 260718A: SVOM/VT optical upper limits
  74. GRB 260718A: SVOM/VT optical upper limits from VHF data
  75. GRB 260718A: SVOM detection of a burst
  76. GRB 260714B: SVOM/GRM observation
  77. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  78. GRB 260714B: GECAM-B observation of a burst
  79. GRB 260618B: EP-FXT follow-up observation upper limit
  80. GRB 260714B: COLIBRÍ optical counterpart candidate
  81. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
  82. SVOM sb26071506: Global MASTER-Net observations report
  83. sb26071506: SVOM detection of a X-ray transient
  84. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  85. GRB 260715A: Fermi GBM Final Real-time Localization
  86. EP260703a: SVOM/ECLAIRs Upper Limit
  87. GRB 260710A: AstroSat CZTI detection
  88. GRB 260709A: AstroSat CZTI detection
  89. GRB 260714B: AstroSat CZTI detection
  90. GRB 260714B: Fermi-LAT detection
  91. GRB 260714B: Fermi GBM Detection
  92. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  93. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  94. GRB 260714B: Fermi GBM Final Real-time Localization
  95. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  96. GRB 260706A: ATCA detection of possible radio counterpart
  97. GRB 260705A: ATCA radio observations
  98. GRB 260714A: Fermi GBM Final Real-time Localization
  99. EP260713a: Einstein Probe detection of an X-ray transient
  100. GRB 260619A: SVOM/VT continuous optical observations

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