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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. GRB 260714B: SVOM/GRM observation
  2. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  3. GRB 260714B: GECAM-B observation of a burst
  4. GRB 260618B: EP-FXT follow-up observation upper limit
  5. GRB 260714B: COLIBRÍ optical counterpart candidate
  6. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
  7. SVOM sb26071506: Global MASTER-Net observations report
  8. sb26071506: SVOM detection of a X-ray transient
  9. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  10. GRB 260715A: Fermi GBM Final Real-time Localization
  11. EP260703a: SVOM/ECLAIRs Upper Limit
  12. GRB 260710A: AstroSat CZTI detection
  13. GRB 260709A: AstroSat CZTI detection
  14. GRB 260714B: AstroSat CZTI detection
  15. GRB 260714B: Fermi-LAT detection
  16. GRB 260714B: Fermi GBM Detection
  17. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  18. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  19. GRB 260714B: Fermi GBM Final Real-time Localization
  20. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  21. GRB 260706A: ATCA detection of possible radio counterpart
  22. GRB 260705A: ATCA radio observations
  23. GRB 260714A: Fermi GBM Final Real-time Localization
  24. EP260713a: Einstein Probe detection of an X-ray transient
  25. GRB 260619A: SVOM/VT continuous optical observations
  26. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  27. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  28. EP260623a: KAIT optical observations
  29. EP260711a: EP-FXT follow-up observation
  30. GRB 260708A: GRANDMA Optical Observations
  31. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  32. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  33. GRB 260710A: Insight-HXMT/HE detection
  34. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  35. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  36. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  37. GRB 260708A: LCO optical observations
  38. EP260711a: Einstein Probe detection of an X-ray transient
  39. GRB 260710A: Fermi GBM Detection
  40. GRB 260709A: SVOM/GRM detection
  41. GRB 260709A: GECAM-B observation
  42. The EP-WXT trigger 01709274666 is likely a new outburst of the CV SS Cyg
  43. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  44. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  45. GRB 260705C: AstroSat CZTI detection
  46. GRB 260710A: Fermi GBM Final Real-time Localization
  47. GRB 260708A: Glowbug gamma-ray detection
  48. GRB 260704A: SVOM/ECLAIRs refined analysis
  49. GRB 260706A : GRANDMA Upper limits
  50. GRB 260708A: Kilonova-Catcher optical afterglow detection
  51. GRB 260708A: GECAM-B observation of a burst
  52. IceCube-260708A: One candidate from the Zwicky Transient Facility
  53. GRB 260708A: Fermi-GBM observation
  54. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  55. IceCube Alert 260709A: Global MASTER-Net observations report
  56. GRB 260709A: Fermi GBM Final Real-time Localization
  57. IceCube-260708A - IceCube observation of a high-energy neutrino candidate track-like event
  58. LAT GRB260708.42: Global MASTER-Net observations report
  59. GRB260708B: MAXI/GSC detection
  60. GRB 260708A: Fermi-LAT detection
  61. GRB 260705B: SVOM/GRM observation
  62. GRB 260708A: Fermi-GBM detection
  63. GRB 260706A: Further EP-FXT follow-up observation
  64. GRB 260706A: SVOM/VT optical upper limits
  65. EP260707a (by EP-FXT): NOT optical upper limit
  66. EP260707a is not a real source
  67. EP260707a: LCOGT Optical Upper Limit
  68. EP260707a: TRT optical upper limit
  69. Fermi GBM trigger 805087514/260707142 (GRB 260707A) is not a GRB
  70. EP260707a: Einstein Probe detection of an X-ray transient
  71. Nova AT2026oyp (ASASSN-26dt): Pre-outburst Swift UVOT observation
  72. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  73. GRB 260705C: Glowbug gamma-ray detection of a short burst
  74. GRB 260706A: SVOM/ECLAIRs refined analysis
  75. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  76. GRB 260706A: SVOM/GRM observation
  77. GRB 260706A: REM optical/NIR observations
  78. IceCube-260704A: No candidates from the Zwicky Transient Facility
  79. GRB 260706A: LCO optical upper limit
  80. GRB 260706A: EP-FXT follow-up observation
  81. GRB 260707A: Fermi GBM Final Real-time Localization
  82. The EP-WXT trigger 01709274151 is likely a flaring star
  83. The EP-WXT trigger 01709274141 is likely a flaring star
  84. GRB 260706A: Fermi GBM Observation
  85. IceCube-260704A: Upper limits from a search for additional neutrino events in IceCube
  86. IPN triangulation of GRB 260627A
  87. GRB 260705A: SVOM/ECLAIRs refined analysis
  88. GRB 260706A: SVOM detection of a burst
  89. GRB 260706A: Fermi GBM Final Real-time Localization
  90. The EP-WXT trigger 01709274014: KAIT confirmation of a stellar flare
  91. The EP-WXT trigger 01709274014 is likely a flaring star
  92. IceCube260704A: OHP/T193 optical observations
  93. GRB 260705A: LCO optical upper limits
  94. GRB 260704A: NOT optical upper limits
  95. GRB 260705C: Fermi GBM Final Localization
  96. GRB 260705B: Fermi GBM Final Real-time Localization
  97. Fermi GBM Sub-Threshold Detection of GRB 260705A
  98. GRB 260705A: SVOM detection of a burst
  99. GRB 260704A: EP-FXT follow-up observation
  100. GRB 260629A: SVOM/GRM observation of a short burst

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