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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. EP260731a: Einstein Probe detection of an X-ray transient
  2. GRB 260727A: SVOM/ECLAIRs refined analysis
  3. GRB 260726A: SVOM/ECLAIRs refined analysis
  4. GRB260730A: Fermi GBM Final Localization
  5. EP260728a: COLIBRÍ optical upper limit
  6. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  7. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  8. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  9. EP260729a: Einstein Probe detection of an X-ray transient
  10. EP260727a: SAO RAS optical observations
  11. GRB 260727A: AbAO and SAO RAS optical observations
  12. EP260728a: EP-FXT follow-up observation
  13. GRB 260726A: EP-FXT follow-up observations
  14. EP260728a: Einstein Probe detection of a fast X-ray transient
  15. GRB 260727A: SVOM/GRM observation
  16. GRB 260726A: Fermi GBM Observation
  17. EP260727a: 1.5m OSN optical counterpart detection
  18. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  19. EP260727a: OHP/T193 optical observations
  20. Konus-Wind detection of GRB 260727A
  21. GRB 260726A: Liverpool Telescope optical observations
  22. GRB 260727A: Liverpool Telescope optical upper limits
  23. EP260727a: Liverpool Telescope confirmation of optical counterpart
  24. EP260727a: NUTTELA-TAO Early Optical Limits
  25. GRB 260728A: Fermi GBM Final Localization
  26. GRB 260727A: EP/FXT follow-up observations
  27. EP260727a: Einstein Probe detection of an X-ray transient
  28. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  29. GRB 260727A: Glowbug gamma-ray detection
  30. GRB 260726A: J-band upper limit with WINTER
  31. GRB 260727A: J-band upper limit with WINTER
  32. GRB 260726A: SVOM/VT optical candidate
  33. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  34. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  35. EP260723a: SVOM/ECLAIRs Upper Limit
  36. GRB 260727A: GOTO early optical upper limit
  37. GRB 260727A: AstroSat CZTI detection
  38. GRB 260727A: Kilonova-Catcher optical upper limit
  39. GRB 260727A: LCO optical upper limits
  40. GRB 260727B: Fermi GBM Final Real-time Localization
  41. Fermi GRB 260726A: Global MASTER-Net observations report
  42. GRB 260727A: SVOM detection of a bright long burst
  43. GRB 260726A: SVOM detection of a burst
  44. GRB 260726A: Fermi GBM Final Real-time Localization
  45. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  46. EP260723a: further EP-FXT follow-up observation
  47. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  48. EP260725a: EP-WXT detection of an X-ray transient
  49. GRB 260616A: cubesat Avion detection
  50. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  51. GRB 260602B: cubesat Avion detection
  52. GRB 260601A: cubesat Avion detection
  53. EP260723a: EP-FXT follow-up observation
  54. IPN triangulation of GRB 260706B
  55. GRB 260718A: SVOM/ECLAIRs refined analysis
  56. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  57. EP260723a: SVOM/VT optical observation
  58. EP260723a: COLIBRÍ optical observations
  59. EP260723a: NOT optical conterpart confirmation
  60. EP260723a: Liverpool Telescope likely optical counterpart
  61. EP260723a: EP-WXT detection of a fast X-ray transient
  62. GRB 260723A: Fermi GBM Final Localization
  63. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  64. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  65. IceCube Alert 260722A: Global MASTER-Net observations report
  66. Konus-Wind detection of GRB 260721A
  67. GRB 260722A: Fermi GBM Final Real-time Localization
  68. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  69. Fermi GBM trigger 806384210/260722151 is not a GRB
  70. GRB 260721A: NuSTAR detection of prompt emission
  71. Konus-Wind detection of GRB 260714B
  72. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  73. GRB 260705A: Retraction of optical counterpart
  74. GRB 260714B: Insight-HXMT/HE detection
  75. GRB 260718A: EP-FXT follow-up observation
  76. Fermi trigger No 806104130: Global MASTER-Net observations report
  77. Fermi GRB 260718A: Global MASTER-Net observations report
  78. GRB 260718A: LCO optical upper limits
  79. GRB 260711A: SVOM/GRM observation
  80. GRB 260710A: SVOM/GRM observation
  81. GRB 260718A: Fermi GBM Observation
  82. GRB 260718A : GRANDMA and KNC upper limits
  83. GRB 260718A: SVOM/VT optical upper limits
  84. GRB 260718A: SVOM/VT optical upper limits from VHF data
  85. GRB 260718A: SVOM detection of a burst
  86. GRB 260714B: SVOM/GRM observation
  87. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  88. GRB 260714B: GECAM-B observation of a burst
  89. GRB 260618B: EP-FXT follow-up observation upper limit
  90. GRB 260714B: COLIBRÍ optical counterpart candidate
  91. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
  92. SVOM sb26071506: Global MASTER-Net observations report
  93. sb26071506: SVOM detection of a X-ray transient
  94. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  95. GRB 260715A: Fermi GBM Final Real-time Localization
  96. EP260703a: SVOM/ECLAIRs Upper Limit
  97. GRB 260710A: AstroSat CZTI detection
  98. GRB 260709A: AstroSat CZTI detection
  99. GRB 260714B: AstroSat CZTI detection
  100. GRB 260714B: Fermi-LAT detection

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