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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. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  2. GRB 260730B: AstroSat CZTI detection
  3. EP260731a: COLIBRÍ optical upper limit
  4. EP260731a: NOT optical upper limit
  5. GRB 260730B: NuSTAR detection of prompt emission
  6. EP260731a: Einstein Probe detection of an X-ray transient
  7. GRB 260727A: SVOM/ECLAIRs refined analysis
  8. GRB 260726A: SVOM/ECLAIRs refined analysis
  9. GRB260730A: Fermi GBM Final Localization
  10. EP260728a: COLIBRÍ optical upper limit
  11. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  12. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  13. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  14. EP260729a: Einstein Probe detection of an X-ray transient
  15. EP260727a: SAO RAS optical observations
  16. GRB 260727A: AbAO and SAO RAS optical observations
  17. EP260728a: EP-FXT follow-up observation
  18. GRB 260726A: EP-FXT follow-up observations
  19. EP260728a: Einstein Probe detection of a fast X-ray transient
  20. GRB 260727A: SVOM/GRM observation
  21. GRB 260726A: Fermi GBM Observation
  22. EP260727a: 1.5m OSN optical counterpart detection
  23. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  24. EP260727a: OHP/T193 optical observations
  25. Konus-Wind detection of GRB 260727A
  26. GRB 260726A: Liverpool Telescope optical observations
  27. GRB 260727A: Liverpool Telescope optical upper limits
  28. EP260727a: Liverpool Telescope confirmation of optical counterpart
  29. EP260727a: NUTTELA-TAO Early Optical Limits
  30. GRB 260728A: Fermi GBM Final Localization
  31. GRB 260727A: EP/FXT follow-up observations
  32. EP260727a: Einstein Probe detection of an X-ray transient
  33. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  34. GRB 260727A: Glowbug gamma-ray detection
  35. GRB 260726A: J-band upper limit with WINTER
  36. GRB 260727A: J-band upper limit with WINTER
  37. GRB 260726A: SVOM/VT optical candidate
  38. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  39. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  40. EP260723a: SVOM/ECLAIRs Upper Limit
  41. GRB 260727A: GOTO early optical upper limit
  42. GRB 260727A: AstroSat CZTI detection
  43. GRB 260727A: Kilonova-Catcher optical upper limit
  44. GRB 260727A: LCO optical upper limits
  45. GRB 260727B: Fermi GBM Final Real-time Localization
  46. Fermi GRB 260726A: Global MASTER-Net observations report
  47. GRB 260727A: SVOM detection of a bright long burst
  48. GRB 260726A: SVOM detection of a burst
  49. GRB 260726A: Fermi GBM Final Real-time Localization
  50. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  51. EP260723a: further EP-FXT follow-up observation
  52. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  53. EP260725a: EP-WXT detection of an X-ray transient
  54. GRB 260616A: cubesat Avion detection
  55. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  56. GRB 260602B: cubesat Avion detection
  57. GRB 260601A: cubesat Avion detection
  58. EP260723a: EP-FXT follow-up observation
  59. IPN triangulation of GRB 260706B
  60. GRB 260718A: SVOM/ECLAIRs refined analysis
  61. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  62. EP260723a: SVOM/VT optical observation
  63. EP260723a: COLIBRÍ optical observations
  64. EP260723a: NOT optical conterpart confirmation
  65. EP260723a: Liverpool Telescope likely optical counterpart
  66. EP260723a: EP-WXT detection of a fast X-ray transient
  67. GRB 260723A: Fermi GBM Final Localization
  68. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  69. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  70. IceCube Alert 260722A: Global MASTER-Net observations report
  71. Konus-Wind detection of GRB 260721A
  72. GRB 260722A: Fermi GBM Final Real-time Localization
  73. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  74. Fermi GBM trigger 806384210/260722151 is not a GRB
  75. GRB 260721A: NuSTAR detection of prompt emission
  76. Konus-Wind detection of GRB 260714B
  77. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  78. GRB 260705A: Retraction of optical counterpart
  79. GRB 260714B: Insight-HXMT/HE detection
  80. GRB 260718A: EP-FXT follow-up observation
  81. Fermi trigger No 806104130: Global MASTER-Net observations report
  82. Fermi GRB 260718A: Global MASTER-Net observations report
  83. GRB 260718A: LCO optical upper limits
  84. GRB 260711A: SVOM/GRM observation
  85. GRB 260710A: SVOM/GRM observation
  86. GRB 260718A: Fermi GBM Observation
  87. GRB 260718A : GRANDMA and KNC upper limits
  88. GRB 260718A: SVOM/VT optical upper limits
  89. GRB 260718A: SVOM/VT optical upper limits from VHF data
  90. GRB 260718A: SVOM detection of a burst
  91. GRB 260714B: SVOM/GRM observation
  92. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  93. GRB 260714B: GECAM-B observation of a burst
  94. GRB 260618B: EP-FXT follow-up observation upper limit
  95. GRB 260714B: COLIBRÍ optical counterpart candidate
  96. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
  97. SVOM sb26071506: Global MASTER-Net observations report
  98. sb26071506: SVOM detection of a X-ray transient
  99. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  100. GRB 260715A: Fermi GBM Final Real-time Localization

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