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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"

32501 results found.

  1. GRB 260727A: EP/FXT follow-up observations
  2. EP260727a: Einstein Probe detection of an X-ray transient
  3. GRB 260727A: Glowbug gamma-ray detection
  4. GRB 260726A: J-band upper limit with WINTER
  5. GRB 260727A: J-band upper limit with WINTER
  6. GRB 260726A: SVOM/VT optical candidate
  7. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  8. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  9. EP260723a: SVOM/ECLAIRs Upper Limit
  10. GRB 260727A: GOTO early optical upper limit
  11. GRB 260727A: AstroSat CZTI detection
  12. GRB 260727A: Kilonova-Catcher optical upper limit
  13. GRB 260727A: LCO optical upper limits
  14. Fermi GRB 260726A: Global MASTER-Net observations report
  15. GRB 260726A: SVOM detection of a burst
  16. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  17. EP260723a: further EP-FXT follow-up observation
  18. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  19. GRB 260616A: cubesat Avion detection
  20. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  21. GRB 260602B: cubesat Avion detection
  22. GRB 260601A: cubesat Avion detection
  23. EP260723a: EP-FXT follow-up observation
  24. IPN triangulation of GRB 260706B
  25. GRB 260718A: SVOM/ECLAIRs refined analysis
  26. EP260723a: SVOM/VT optical observation
  27. EP260723a: COLIBRÍ optical observations
  28. EP260723a: NOT optical conterpart confirmation
  29. EP260723a: Liverpool Telescope likely optical counterpart
  30. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  31. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  32. Konus-Wind detection of GRB 260721A
  33. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  34. GRB 260721A: NuSTAR detection of prompt emission
  35. Konus-Wind detection of GRB 260714B
  36. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  37. GRB 260705A: Retraction of optical counterpart
  38. GRB 260714B: Insight-HXMT/HE detection
  39. GRB 260718A: EP-FXT follow-up observation
  40. Fermi GRB 260718A: Global MASTER-Net observations report
  41. GRB 260718A: LCO optical upper limits
  42. GRB 260711A: SVOM/GRM observation
  43. GRB 260710A: SVOM/GRM observation
  44. GRB 260718A: Fermi GBM Observation
  45. GRB 260718A : GRANDMA and KNC upper limits
  46. GRB 260718A: SVOM/VT optical upper limits
  47. GRB 260718A: SVOM/VT optical upper limits from VHF data
  48. GRB 260718A: SVOM detection of a burst
  49. GRB 260714B: SVOM/GRM observation
  50. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  51. GRB 260714B: GECAM-B observation of a burst
  52. GRB 260618B: EP-FXT follow-up observation upper limit
  53. GRB 260714B: COLIBRÍ optical counterpart candidate
  54. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
  55. SVOM sb26071506: Global MASTER-Net observations report
  56. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  57. EP260703a: SVOM/ECLAIRs Upper Limit
  58. GRB 260710A: AstroSat CZTI detection
  59. GRB 260709A: AstroSat CZTI detection
  60. GRB 260714B: AstroSat CZTI detection
  61. GRB 260714B: Fermi-LAT detection
  62. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  63. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  64. GRB 260706A: ATCA detection of possible radio counterpart
  65. GRB 260705A: ATCA radio observations
  66. GRB 260619A: SVOM/VT continuous optical observations
  67. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  68. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  69. EP260623a: KAIT optical observations
  70. EP260711a: EP-FXT follow-up observation
  71. GRB 260708A: GRANDMA Optical Observations
  72. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  73. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  74. GRB 260710A: Insight-HXMT/HE detection
  75. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  76. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  77. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  78. GRB 260708A: LCO optical observations
  79. GRB 260710A: Fermi GBM Detection
  80. GRB 260709A: SVOM/GRM detection
  81. GRB 260709A: GECAM-B observation
  82. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  83. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  84. GRB 260705C: AstroSat CZTI detection
  85. GRB 260708A: Glowbug gamma-ray detection
  86. GRB 260704A: SVOM/ECLAIRs refined analysis
  87. GRB 260706A : GRANDMA Upper limits
  88. GRB 260708A: Kilonova-Catcher optical afterglow detection
  89. GRB 260708A: GECAM-B observation of a burst
  90. IceCube-260708A: One candidate from the Zwicky Transient Facility
  91. GRB 260708A: Fermi-GBM observation
  92. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  93. IceCube-260708A - IceCube observation of a high-energy neutrino candidate track-like event
  94. GRB 260708A: Fermi-LAT detection
  95. GRB 260705B: SVOM/GRM observation
  96. GRB 260706A: Further EP-FXT follow-up observation
  97. GRB 260706A: SVOM/VT optical upper limits
  98. EP260707a (by EP-FXT): NOT optical upper limit
  99. EP260707a is not a real source
  100. EP260707a: LCOGT Optical Upper Limit

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