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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. Konus-Wind detection of GRB 260714B
  2. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  3. GRB 260705A: Retraction of optical counterpart
  4. GRB 260714B: Insight-HXMT/HE detection
  5. GRB 260718A: EP-FXT follow-up observation
  6. Fermi trigger No 806104130: Global MASTER-Net observations report
  7. Fermi GRB 260718A: Global MASTER-Net observations report
  8. GRB 260718A: LCO optical upper limits
  9. GRB 260711A: SVOM/GRM observation
  10. GRB 260710A: SVOM/GRM observation
  11. GRB 260718A: Fermi GBM Observation
  12. GRB 260718A : GRANDMA and KNC upper limits
  13. GRB 260718A: SVOM/VT optical upper limits
  14. GRB 260718A: SVOM/VT optical upper limits from VHF data
  15. GRB 260718A: SVOM detection of a burst
  16. GRB 260714B: SVOM/GRM observation
  17. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  18. GRB 260714B: GECAM-B observation of a burst
  19. GRB 260618B: EP-FXT follow-up observation upper limit
  20. GRB 260714B: COLIBRÍ optical counterpart candidate
  21. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
  22. SVOM sb26071506: Global MASTER-Net observations report
  23. sb26071506: SVOM detection of a X-ray transient
  24. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  25. GRB 260715A: Fermi GBM Final Real-time Localization
  26. EP260703a: SVOM/ECLAIRs Upper Limit
  27. GRB 260710A: AstroSat CZTI detection
  28. GRB 260709A: AstroSat CZTI detection
  29. GRB 260714B: AstroSat CZTI detection
  30. GRB 260714B: Fermi-LAT detection
  31. GRB 260714B: Fermi GBM Detection
  32. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  33. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  34. GRB 260714B: Fermi GBM Final Real-time Localization
  35. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  36. GRB 260706A: ATCA detection of possible radio counterpart
  37. GRB 260705A: ATCA radio observations
  38. GRB 260714A: Fermi GBM Final Real-time Localization
  39. EP260713a: Einstein Probe detection of an X-ray transient
  40. GRB 260619A: SVOM/VT continuous optical observations
  41. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  42. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  43. EP260623a: KAIT optical observations
  44. EP260711a: EP-FXT follow-up observation
  45. GRB 260708A: GRANDMA Optical Observations
  46. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  47. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  48. GRB 260710A: Insight-HXMT/HE detection
  49. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  50. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  51. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  52. GRB 260708A: LCO optical observations
  53. EP260711a: Einstein Probe detection of an X-ray transient
  54. GRB 260710A: Fermi GBM Detection
  55. GRB 260709A: SVOM/GRM detection
  56. GRB 260709A: GECAM-B observation
  57. The EP-WXT trigger 01709274666 is likely a new outburst of the CV SS Cyg
  58. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  59. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  60. GRB 260705C: AstroSat CZTI detection
  61. GRB 260710A: Fermi GBM Final Real-time Localization
  62. GRB 260708A: Glowbug gamma-ray detection
  63. GRB 260704A: SVOM/ECLAIRs refined analysis
  64. GRB 260706A : GRANDMA Upper limits
  65. GRB 260708A: Kilonova-Catcher optical afterglow detection
  66. GRB 260708A: GECAM-B observation of a burst
  67. IceCube-260708A: One candidate from the Zwicky Transient Facility
  68. GRB 260708A: Fermi-GBM observation
  69. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  70. IceCube Alert 260709A: Global MASTER-Net observations report
  71. GRB 260709A: Fermi GBM Final Real-time Localization
  72. IceCube-260708A - IceCube observation of a high-energy neutrino candidate track-like event
  73. LAT GRB260708.42: Global MASTER-Net observations report
  74. GRB260708B: MAXI/GSC detection
  75. GRB 260708A: Fermi-LAT detection
  76. GRB 260705B: SVOM/GRM observation
  77. GRB 260708A: Fermi-GBM detection
  78. GRB 260706A: Further EP-FXT follow-up observation
  79. GRB 260706A: SVOM/VT optical upper limits
  80. EP260707a (by EP-FXT): NOT optical upper limit
  81. EP260707a is not a real source
  82. EP260707a: LCOGT Optical Upper Limit
  83. EP260707a: TRT optical upper limit
  84. Fermi GBM trigger 805087514/260707142 (GRB 260707A) is not a GRB
  85. EP260707a: Einstein Probe detection of an X-ray transient
  86. Nova AT2026oyp (ASASSN-26dt): Pre-outburst Swift UVOT observation
  87. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  88. GRB 260705C: Glowbug gamma-ray detection of a short burst
  89. GRB 260706A: SVOM/ECLAIRs refined analysis
  90. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  91. GRB 260706A: SVOM/GRM observation
  92. GRB 260706A: REM optical/NIR observations
  93. IceCube-260704A: No candidates from the Zwicky Transient Facility
  94. GRB 260706A: LCO optical upper limit
  95. GRB 260706A: EP-FXT follow-up observation
  96. GRB 260707A: Fermi GBM Final Real-time Localization
  97. The EP-WXT trigger 01709274151 is likely a flaring star
  98. The EP-WXT trigger 01709274141 is likely a flaring star
  99. GRB 260706A: Fermi GBM Observation
  100. IceCube-260704A: Upper limits from a search for additional neutrino events in IceCube

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