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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: SVOM/ECLAIRs refined analysis
  2. GRB260730A: Fermi GBM Final Localization
  3. EP260728a: COLIBRÍ optical upper limit
  4. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  5. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  6. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  7. EP260729a: Einstein Probe detection of an X-ray transient
  8. EP260727a: SAO RAS optical observations
  9. GRB 260727A: AbAO and SAO RAS optical observations
  10. EP260728a: EP-FXT follow-up observation
  11. GRB 260726A: EP-FXT follow-up observations
  12. EP260728a: Einstein Probe detection of a fast X-ray transient
  13. GRB 260727A: SVOM/GRM observation
  14. GRB 260726A: Fermi GBM Observation
  15. EP260727a: 1.5m OSN optical counterpart detection
  16. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  17. EP260727a: OHP/T193 optical observations
  18. Konus-Wind detection of GRB 260727A
  19. GRB 260726A: Liverpool Telescope optical observations
  20. GRB 260727A: Liverpool Telescope optical upper limits
  21. EP260727a: Liverpool Telescope confirmation of optical counterpart
  22. EP260727a: NUTTELA-TAO Early Optical Limits
  23. GRB 260728A: Fermi GBM Final Localization
  24. GRB 260727A: EP/FXT follow-up observations
  25. EP260727a: Einstein Probe detection of an X-ray transient
  26. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  27. GRB 260727A: Glowbug gamma-ray detection
  28. GRB 260726A: J-band upper limit with WINTER
  29. GRB 260727A: J-band upper limit with WINTER
  30. GRB 260726A: SVOM/VT optical candidate
  31. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  32. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  33. EP260723a: SVOM/ECLAIRs Upper Limit
  34. GRB 260727A: GOTO early optical upper limit
  35. GRB 260727A: AstroSat CZTI detection
  36. GRB 260727A: Kilonova-Catcher optical upper limit
  37. GRB 260727A: LCO optical upper limits
  38. GRB 260727B: Fermi GBM Final Real-time Localization
  39. Fermi GRB 260726A: Global MASTER-Net observations report
  40. GRB 260727A: SVOM detection of a bright long burst
  41. GRB 260726A: SVOM detection of a burst
  42. GRB 260726A: Fermi GBM Final Real-time Localization
  43. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  44. EP260723a: further EP-FXT follow-up observation
  45. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  46. EP260725a: EP-WXT detection of an X-ray transient
  47. GRB 260616A: cubesat Avion detection
  48. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  49. GRB 260602B: cubesat Avion detection
  50. GRB 260601A: cubesat Avion detection
  51. EP260723a: EP-FXT follow-up observation
  52. IPN triangulation of GRB 260706B
  53. GRB 260718A: SVOM/ECLAIRs refined analysis
  54. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  55. EP260723a: SVOM/VT optical observation
  56. EP260723a: COLIBRÍ optical observations
  57. EP260723a: NOT optical conterpart confirmation
  58. EP260723a: Liverpool Telescope likely optical counterpart
  59. EP260723a: EP-WXT detection of a fast X-ray transient
  60. GRB 260723A: Fermi GBM Final Localization
  61. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  62. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  63. IceCube Alert 260722A: Global MASTER-Net observations report
  64. Konus-Wind detection of GRB 260721A
  65. GRB 260722A: Fermi GBM Final Real-time Localization
  66. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  67. Fermi GBM trigger 806384210/260722151 is not a GRB
  68. GRB 260721A: NuSTAR detection of prompt emission
  69. Konus-Wind detection of GRB 260714B
  70. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  71. GRB 260705A: Retraction of optical counterpart
  72. GRB 260714B: Insight-HXMT/HE detection
  73. GRB 260718A: EP-FXT follow-up observation
  74. Fermi trigger No 806104130: Global MASTER-Net observations report
  75. Fermi GRB 260718A: Global MASTER-Net observations report
  76. GRB 260718A: LCO optical upper limits
  77. GRB 260711A: SVOM/GRM observation
  78. GRB 260710A: SVOM/GRM observation
  79. GRB 260718A: Fermi GBM Observation
  80. GRB 260718A : GRANDMA and KNC upper limits
  81. GRB 260718A: SVOM/VT optical upper limits
  82. GRB 260718A: SVOM/VT optical upper limits from VHF data
  83. GRB 260718A: SVOM detection of a burst
  84. GRB 260714B: SVOM/GRM observation
  85. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  86. GRB 260714B: GECAM-B observation of a burst
  87. GRB 260618B: EP-FXT follow-up observation upper limit
  88. GRB 260714B: COLIBRÍ optical counterpart candidate
  89. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
  90. SVOM sb26071506: Global MASTER-Net observations report
  91. sb26071506: SVOM detection of a X-ray transient
  92. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  93. GRB 260715A: Fermi GBM Final Real-time Localization
  94. EP260703a: SVOM/ECLAIRs Upper Limit
  95. GRB 260710A: AstroSat CZTI detection
  96. GRB 260709A: AstroSat CZTI detection
  97. GRB 260714B: AstroSat CZTI detection
  98. GRB 260714B: Fermi-LAT detection
  99. GRB 260714B: Fermi GBM Detection
  100. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)

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