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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. EP260723a: NOT optical conterpart confirmation
  2. EP260723a: Liverpool Telescope likely optical counterpart
  3. EP260723a: EP-WXT detection of a fast X-ray transient
  4. GRB 260723A: Fermi GBM Final Localization
  5. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  6. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  7. IceCube Alert 260722A: Global MASTER-Net observations report
  8. Konus-Wind detection of GRB 260721A
  9. GRB 260722A: Fermi GBM Final Real-time Localization
  10. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  11. Fermi GBM trigger 806384210/260722151 is not a GRB
  12. GRB 260721A: NuSTAR detection of prompt emission
  13. Konus-Wind detection of GRB 260714B
  14. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  15. GRB 260705A: Retraction of optical counterpart
  16. GRB 260714B: Insight-HXMT/HE detection
  17. GRB 260718A: EP-FXT follow-up observation
  18. Fermi trigger No 806104130: Global MASTER-Net observations report
  19. Fermi GRB 260718A: Global MASTER-Net observations report
  20. GRB 260718A: LCO optical upper limits
  21. GRB 260711A: SVOM/GRM observation
  22. GRB 260710A: SVOM/GRM observation
  23. GRB 260718A: Fermi GBM Observation
  24. GRB 260718A : GRANDMA and KNC upper limits
  25. GRB 260718A: SVOM/VT optical upper limits
  26. GRB 260718A: SVOM/VT optical upper limits from VHF data
  27. GRB 260718A: SVOM detection of a burst
  28. GRB 260714B: SVOM/GRM observation
  29. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  30. GRB 260714B: GECAM-B observation of a burst
  31. GRB 260618B: EP-FXT follow-up observation upper limit
  32. GRB 260714B: COLIBRÍ optical counterpart candidate
  33. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
  34. SVOM sb26071506: Global MASTER-Net observations report
  35. sb26071506: SVOM detection of a X-ray transient
  36. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  37. GRB 260715A: Fermi GBM Final Real-time Localization
  38. EP260703a: SVOM/ECLAIRs Upper Limit
  39. GRB 260710A: AstroSat CZTI detection
  40. GRB 260709A: AstroSat CZTI detection
  41. GRB 260714B: AstroSat CZTI detection
  42. GRB 260714B: Fermi-LAT detection
  43. GRB 260714B: Fermi GBM Detection
  44. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  45. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  46. GRB 260714B: Fermi GBM Final Real-time Localization
  47. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  48. GRB 260706A: ATCA detection of possible radio counterpart
  49. GRB 260705A: ATCA radio observations
  50. GRB 260714A: Fermi GBM Final Real-time Localization
  51. EP260713a: Einstein Probe detection of an X-ray transient
  52. GRB 260619A: SVOM/VT continuous optical observations
  53. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  54. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  55. EP260623a: KAIT optical observations
  56. EP260711a: EP-FXT follow-up observation
  57. GRB 260708A: GRANDMA Optical Observations
  58. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  59. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  60. GRB 260710A: Insight-HXMT/HE detection
  61. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  62. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  63. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  64. GRB 260708A: LCO optical observations
  65. EP260711a: Einstein Probe detection of an X-ray transient
  66. GRB 260710A: Fermi GBM Detection
  67. GRB 260709A: SVOM/GRM detection
  68. GRB 260709A: GECAM-B observation
  69. The EP-WXT trigger 01709274666 is likely a new outburst of the CV SS Cyg
  70. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  71. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  72. GRB 260705C: AstroSat CZTI detection
  73. GRB 260710A: Fermi GBM Final Real-time Localization
  74. GRB 260708A: Glowbug gamma-ray detection
  75. GRB 260704A: SVOM/ECLAIRs refined analysis
  76. GRB 260706A : GRANDMA Upper limits
  77. GRB 260708A: Kilonova-Catcher optical afterglow detection
  78. GRB 260708A: GECAM-B observation of a burst
  79. IceCube-260708A: One candidate from the Zwicky Transient Facility
  80. GRB 260708A: Fermi-GBM observation
  81. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  82. IceCube Alert 260709A: Global MASTER-Net observations report
  83. GRB 260709A: Fermi GBM Final Real-time Localization
  84. IceCube-260708A - IceCube observation of a high-energy neutrino candidate track-like event
  85. LAT GRB260708.42: Global MASTER-Net observations report
  86. GRB260708B: MAXI/GSC detection
  87. GRB 260708A: Fermi-LAT detection
  88. GRB 260705B: SVOM/GRM observation
  89. GRB 260708A: Fermi-GBM detection
  90. GRB 260706A: Further EP-FXT follow-up observation
  91. GRB 260706A: SVOM/VT optical upper limits
  92. EP260707a (by EP-FXT): NOT optical upper limit
  93. EP260707a is not a real source
  94. EP260707a: LCOGT Optical Upper Limit
  95. EP260707a: TRT optical upper limit
  96. Fermi GBM trigger 805087514/260707142 (GRB 260707A) is not a GRB
  97. EP260707a: Einstein Probe detection of an X-ray transient
  98. Nova AT2026oyp (ASASSN-26dt): Pre-outburst Swift UVOT observation
  99. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  100. GRB 260705C: Glowbug gamma-ray detection of a short burst

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