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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"

32496 results found.

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

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