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

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