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

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