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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: Liverpool Telescope optical observations
  2. GRB 260727A: Liverpool Telescope optical upper limits
  3. EP260727a: Liverpool Telescope confirmation of optical counterpart
  4. EP260727a: NUTTELA-TAO Early Optical Limits
  5. GRB 260728A: Fermi GBM Final Localization
  6. GRB 260727A: EP/FXT follow-up observations
  7. EP260727a: Einstein Probe detection of an X-ray transient
  8. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  9. GRB 260727A: Glowbug gamma-ray detection
  10. GRB 260726A: J-band upper limit with WINTER
  11. GRB 260727A: J-band upper limit with WINTER
  12. GRB 260726A: SVOM/VT optical candidate
  13. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  14. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  15. EP260723a: SVOM/ECLAIRs Upper Limit
  16. GRB 260727A: GOTO early optical upper limit
  17. GRB 260727A: AstroSat CZTI detection
  18. GRB 260727A: Kilonova-Catcher optical upper limit
  19. GRB 260727A: LCO optical upper limits
  20. GRB 260727B: Fermi GBM Final Real-time Localization
  21. Fermi GRB 260726A: Global MASTER-Net observations report
  22. GRB 260727A: SVOM detection of a bright long burst
  23. GRB 260726A: SVOM detection of a burst
  24. GRB 260726A: Fermi GBM Final Real-time Localization
  25. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  26. EP260723a: further EP-FXT follow-up observation
  27. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  28. EP260725a: EP-WXT detection of an X-ray transient
  29. GRB 260616A: cubesat Avion detection
  30. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  31. GRB 260602B: cubesat Avion detection
  32. GRB 260601A: cubesat Avion detection
  33. EP260723a: EP-FXT follow-up observation
  34. IPN triangulation of GRB 260706B
  35. GRB 260718A: SVOM/ECLAIRs refined analysis
  36. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  37. EP260723a: SVOM/VT optical observation
  38. EP260723a: COLIBRÍ optical observations
  39. EP260723a: NOT optical conterpart confirmation
  40. EP260723a: Liverpool Telescope likely optical counterpart
  41. EP260723a: EP-WXT detection of a fast X-ray transient
  42. GRB 260723A: Fermi GBM Final Localization
  43. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  44. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  45. IceCube Alert 260722A: Global MASTER-Net observations report
  46. Konus-Wind detection of GRB 260721A
  47. GRB 260722A: Fermi GBM Final Real-time Localization
  48. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  49. Fermi GBM trigger 806384210/260722151 is not a GRB
  50. GRB 260721A: NuSTAR detection of prompt emission
  51. Konus-Wind detection of GRB 260714B
  52. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  53. GRB 260705A: Retraction of optical counterpart
  54. GRB 260714B: Insight-HXMT/HE detection
  55. GRB 260718A: EP-FXT follow-up observation
  56. Fermi trigger No 806104130: Global MASTER-Net observations report
  57. Fermi GRB 260718A: Global MASTER-Net observations report
  58. GRB 260718A: LCO optical upper limits
  59. GRB 260711A: SVOM/GRM observation
  60. GRB 260710A: SVOM/GRM observation
  61. GRB 260718A: Fermi GBM Observation
  62. GRB 260718A : GRANDMA and KNC upper limits
  63. GRB 260718A: SVOM/VT optical upper limits
  64. GRB 260718A: SVOM/VT optical upper limits from VHF data
  65. GRB 260718A: SVOM detection of a burst
  66. GRB 260714B: SVOM/GRM observation
  67. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  68. GRB 260714B: GECAM-B observation of a burst
  69. GRB 260618B: EP-FXT follow-up observation upper limit
  70. GRB 260714B: COLIBRÍ optical counterpart candidate
  71. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
  72. SVOM sb26071506: Global MASTER-Net observations report
  73. sb26071506: SVOM detection of a X-ray transient
  74. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  75. GRB 260715A: Fermi GBM Final Real-time Localization
  76. EP260703a: SVOM/ECLAIRs Upper Limit
  77. GRB 260710A: AstroSat CZTI detection
  78. GRB 260709A: AstroSat CZTI detection
  79. GRB 260714B: AstroSat CZTI detection
  80. GRB 260714B: Fermi-LAT detection
  81. GRB 260714B: Fermi GBM Detection
  82. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  83. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  84. GRB 260714B: Fermi GBM Final Real-time Localization
  85. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  86. GRB 260706A: ATCA detection of possible radio counterpart
  87. GRB 260705A: ATCA radio observations
  88. GRB 260714A: Fermi GBM Final Real-time Localization
  89. EP260713a: Einstein Probe detection of an X-ray transient
  90. GRB 260619A: SVOM/VT continuous optical observations
  91. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  92. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  93. EP260623a: KAIT optical observations
  94. EP260711a: EP-FXT follow-up observation
  95. GRB 260708A: GRANDMA Optical Observations
  96. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  97. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  98. GRB 260710A: Insight-HXMT/HE detection
  99. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  100. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube

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