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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 260721A
  2. GRB 260722A: Fermi GBM Final Real-time Localization
  3. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  4. Fermi GBM trigger 806384210/260722151 is not a GRB
  5. GRB 260721A: NuSTAR detection of prompt emission
  6. Konus-Wind detection of GRB 260714B
  7. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  8. GRB 260705A: Retraction of optical counterpart
  9. GRB 260714B: Insight-HXMT/HE detection
  10. GRB 260718A: EP-FXT follow-up observation
  11. Fermi trigger No 806104130: Global MASTER-Net observations report
  12. Fermi GRB 260718A: Global MASTER-Net observations report
  13. GRB 260718A: LCO optical upper limits
  14. GRB 260711A: SVOM/GRM observation
  15. GRB 260710A: SVOM/GRM observation
  16. GRB 260718A: Fermi GBM Observation
  17. GRB 260718A : GRANDMA and KNC upper limits
  18. GRB 260718A: SVOM/VT optical upper limits
  19. GRB 260718A: SVOM/VT optical upper limits from VHF data
  20. GRB 260718A: SVOM detection of a burst
  21. GRB 260714B: SVOM/GRM observation
  22. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  23. GRB 260714B: GECAM-B observation of a burst
  24. GRB 260618B: EP-FXT follow-up observation upper limit
  25. GRB 260714B: COLIBRÍ optical counterpart candidate
  26. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
  27. SVOM sb26071506: Global MASTER-Net observations report
  28. sb26071506: SVOM detection of a X-ray transient
  29. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  30. GRB 260715A: Fermi GBM Final Real-time Localization
  31. EP260703a: SVOM/ECLAIRs Upper Limit
  32. GRB 260710A: AstroSat CZTI detection
  33. GRB 260709A: AstroSat CZTI detection
  34. GRB 260714B: AstroSat CZTI detection
  35. GRB 260714B: Fermi-LAT detection
  36. GRB 260714B: Fermi GBM Detection
  37. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  38. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  39. GRB 260714B: Fermi GBM Final Real-time Localization
  40. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  41. GRB 260706A: ATCA detection of possible radio counterpart
  42. GRB 260705A: ATCA radio observations
  43. GRB 260714A: Fermi GBM Final Real-time Localization
  44. EP260713a: Einstein Probe detection of an X-ray transient
  45. GRB 260619A: SVOM/VT continuous optical observations
  46. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  47. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  48. EP260623a: KAIT optical observations
  49. EP260711a: EP-FXT follow-up observation
  50. GRB 260708A: GRANDMA Optical Observations
  51. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  52. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  53. GRB 260710A: Insight-HXMT/HE detection
  54. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  55. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  56. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  57. GRB 260708A: LCO optical observations
  58. EP260711a: Einstein Probe detection of an X-ray transient
  59. GRB 260710A: Fermi GBM Detection
  60. GRB 260709A: SVOM/GRM detection
  61. GRB 260709A: GECAM-B observation
  62. The EP-WXT trigger 01709274666 is likely a new outburst of the CV SS Cyg
  63. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  64. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  65. GRB 260705C: AstroSat CZTI detection
  66. GRB 260710A: Fermi GBM Final Real-time Localization
  67. GRB 260708A: Glowbug gamma-ray detection
  68. GRB 260704A: SVOM/ECLAIRs refined analysis
  69. GRB 260706A : GRANDMA Upper limits
  70. GRB 260708A: Kilonova-Catcher optical afterglow detection
  71. GRB 260708A: GECAM-B observation of a burst
  72. IceCube-260708A: One candidate from the Zwicky Transient Facility
  73. GRB 260708A: Fermi-GBM observation
  74. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  75. IceCube Alert 260709A: Global MASTER-Net observations report
  76. GRB 260709A: Fermi GBM Final Real-time Localization
  77. IceCube-260708A - IceCube observation of a high-energy neutrino candidate track-like event
  78. LAT GRB260708.42: Global MASTER-Net observations report
  79. GRB260708B: MAXI/GSC detection
  80. GRB 260708A: Fermi-LAT detection
  81. GRB 260705B: SVOM/GRM observation
  82. GRB 260708A: Fermi-GBM detection
  83. GRB 260706A: Further EP-FXT follow-up observation
  84. GRB 260706A: SVOM/VT optical upper limits
  85. EP260707a (by EP-FXT): NOT optical upper limit
  86. EP260707a is not a real source
  87. EP260707a: LCOGT Optical Upper Limit
  88. EP260707a: TRT optical upper limit
  89. Fermi GBM trigger 805087514/260707142 (GRB 260707A) is not a GRB
  90. EP260707a: Einstein Probe detection of an X-ray transient
  91. Nova AT2026oyp (ASASSN-26dt): Pre-outburst Swift UVOT observation
  92. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  93. GRB 260705C: Glowbug gamma-ray detection of a short burst
  94. GRB 260706A: SVOM/ECLAIRs refined analysis
  95. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  96. GRB 260706A: SVOM/GRM observation
  97. GRB 260706A: REM optical/NIR observations
  98. IceCube-260704A: No candidates from the Zwicky Transient Facility
  99. GRB 260706A: LCO optical upper limit
  100. GRB 260706A: EP-FXT follow-up observation

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