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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. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  2. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  3. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  4. EP260729a: Einstein Probe detection of an X-ray transient
  5. EP260727a: SAO RAS optical observations
  6. GRB 260727A: AbAO and SAO RAS optical observations
  7. EP260728a: EP-FXT follow-up observation
  8. GRB 260726A: EP-FXT follow-up observations
  9. EP260728a: Einstein Probe detection of a fast X-ray transient
  10. GRB 260727A: SVOM/GRM observation
  11. GRB 260726A: Fermi GBM Observation
  12. EP260727a: 1.5m OSN optical counterpart detection
  13. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  14. EP260727a: OHP/T193 optical observations
  15. Konus-Wind detection of GRB 260727A
  16. GRB 260726A: Liverpool Telescope optical observations
  17. GRB 260727A: Liverpool Telescope optical upper limits
  18. EP260727a: Liverpool Telescope confirmation of optical counterpart
  19. EP260727a: NUTTELA-TAO Early Optical Limits
  20. GRB 260728A: Fermi GBM Final Localization
  21. GRB 260727A: EP/FXT follow-up observations
  22. EP260727a: Einstein Probe detection of an X-ray transient
  23. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  24. GRB 260727A: Glowbug gamma-ray detection
  25. GRB 260726A: J-band upper limit with WINTER
  26. GRB 260727A: J-band upper limit with WINTER
  27. GRB 260726A: SVOM/VT optical candidate
  28. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  29. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  30. EP260723a: SVOM/ECLAIRs Upper Limit
  31. GRB 260727A: GOTO early optical upper limit
  32. GRB 260727A: AstroSat CZTI detection
  33. GRB 260727A: Kilonova-Catcher optical upper limit
  34. GRB 260727A: LCO optical upper limits
  35. GRB 260727B: Fermi GBM Final Real-time Localization
  36. Fermi GRB 260726A: Global MASTER-Net observations report
  37. GRB 260727A: SVOM detection of a bright long burst
  38. GRB 260726A: SVOM detection of a burst
  39. GRB 260726A: Fermi GBM Final Real-time Localization
  40. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  41. EP260723a: further EP-FXT follow-up observation
  42. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  43. EP260725a: EP-WXT detection of an X-ray transient
  44. GRB 260616A: cubesat Avion detection
  45. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  46. GRB 260602B: cubesat Avion detection
  47. GRB 260601A: cubesat Avion detection
  48. EP260723a: EP-FXT follow-up observation
  49. IPN triangulation of GRB 260706B
  50. GRB 260718A: SVOM/ECLAIRs refined analysis
  51. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  52. EP260723a: SVOM/VT optical observation
  53. EP260723a: COLIBRÍ optical observations
  54. EP260723a: NOT optical conterpart confirmation
  55. EP260723a: Liverpool Telescope likely optical counterpart
  56. EP260723a: EP-WXT detection of a fast X-ray transient
  57. GRB 260723A: Fermi GBM Final Localization
  58. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  59. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  60. IceCube Alert 260722A: Global MASTER-Net observations report
  61. Konus-Wind detection of GRB 260721A
  62. GRB 260722A: Fermi GBM Final Real-time Localization
  63. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  64. Fermi GBM trigger 806384210/260722151 is not a GRB
  65. GRB 260721A: NuSTAR detection of prompt emission
  66. Konus-Wind detection of GRB 260714B
  67. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  68. GRB 260705A: Retraction of optical counterpart
  69. GRB 260714B: Insight-HXMT/HE detection
  70. GRB 260718A: EP-FXT follow-up observation
  71. Fermi trigger No 806104130: Global MASTER-Net observations report
  72. Fermi GRB 260718A: Global MASTER-Net observations report
  73. GRB 260718A: LCO optical upper limits
  74. GRB 260711A: SVOM/GRM observation
  75. GRB 260710A: SVOM/GRM observation
  76. GRB 260718A: Fermi GBM Observation
  77. GRB 260718A : GRANDMA and KNC upper limits
  78. GRB 260718A: SVOM/VT optical upper limits
  79. GRB 260718A: SVOM/VT optical upper limits from VHF data
  80. GRB 260718A: SVOM detection of a burst
  81. GRB 260714B: SVOM/GRM observation
  82. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  83. GRB 260714B: GECAM-B observation of a burst
  84. GRB 260618B: EP-FXT follow-up observation upper limit
  85. GRB 260714B: COLIBRÍ optical counterpart candidate
  86. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
  87. SVOM sb26071506: Global MASTER-Net observations report
  88. sb26071506: SVOM detection of a X-ray transient
  89. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  90. GRB 260715A: Fermi GBM Final Real-time Localization
  91. EP260703a: SVOM/ECLAIRs Upper Limit
  92. GRB 260710A: AstroSat CZTI detection
  93. GRB 260709A: AstroSat CZTI detection
  94. GRB 260714B: AstroSat CZTI detection
  95. GRB 260714B: Fermi-LAT detection
  96. GRB 260714B: Fermi GBM Detection
  97. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  98. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  99. GRB 260714B: Fermi GBM Final Real-time Localization
  100. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate

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