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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"

11531 results found.

  1. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  2. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  3. GRB 260710A: Insight-HXMT/HE detection
  4. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  5. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  6. GRB 260708A: LCO optical observations
  7. GRB 260710A: Fermi GBM Detection
  8. GRB 260709A: SVOM/GRM detection
  9. GRB 260709A: GECAM-B observation
  10. GRB 260705C: AstroSat CZTI detection
  11. GRB 260710A: Fermi GBM Final Real-time Localization
  12. GRB 260708A: Glowbug gamma-ray detection
  13. GRB 260706A : GRANDMA Upper limits
  14. GRB 260708A: Kilonova-Catcher optical afterglow detection
  15. GRB 260708A: GECAM-B observation of a burst
  16. GRB 260708A: Fermi-GBM observation
  17. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  18. GRB 260709A: Fermi GBM Final Real-time Localization
  19. IceCube-260708A - IceCube observation of a high-energy neutrino candidate track-like event
  20. GRB 260708A: Fermi-LAT detection
  21. GRB 260705B: SVOM/GRM observation
  22. GRB 260708A: Fermi-GBM detection
  23. GRB 260706A: Further EP-FXT follow-up observation
  24. GRB 260706A: SVOM/VT optical upper limits
  25. Fermi GBM trigger 805087514/260707142 (GRB 260707A) is not a GRB
  26. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  27. GRB 260705C: Glowbug gamma-ray detection of a short burst
  28. GRB 260706A: SVOM/ECLAIRs refined analysis
  29. GRB 260706A: SVOM/GRM observation
  30. GRB 260706A: REM optical/NIR observations
  31. GRB 260706A: LCO optical upper limit
  32. GRB 260706A: EP-FXT follow-up observation
  33. GRB 260707A: Fermi GBM Final Real-time Localization
  34. GRB 260706A: Fermi GBM Observation
  35. GRB 260706A: SVOM detection of a burst
  36. GRB 260706A: Fermi GBM Final Real-time Localization
  37. GRB 260705C: Fermi GBM Final Localization
  38. GRB 260705B: Fermi GBM Final Real-time Localization
  39. Fermi GBM Sub-Threshold Detection of GRB 260705A
  40. GRB 260629A: SVOM/GRM observation of a short burst
  41. GRB 260629A: GECAM-A observation of a short burst
  42. IceCube-260704A - IceCube observation of a high-energy neutrino candidate track-like event
  43. GRB 260629A: AstroSat CZTI detection
  44. GRB 260703B: Fermi GBM Final Localization
  45. Fermi trigger No 804738310: Global MASTER-Net observations report
  46. Fermi GRB 260703A: Global MASTER-Net observations report
  47. GRB 260703A: Fermi GBM Final Localization
  48. GRB 260610B: VLA detection
  49. GRB 260623A: Glowbug gamma-ray detection
  50. GRB 260614B: ATCA Radio Upper Limits
  51. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  52. Fermi trigger No 804552016: Global MASTER-Net observations report
  53. GRB 260701A: Fermi GBM Final Real-time Localization
  54. Fermi GBM trigger 804552016/260630945 is not a GRB
  55. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  56. GRB 260629A: Fermi GBM Final Real-time Localization
  57. Fermi GRB 260628A: Global MASTER-Net observations report
  58. GRB 260628A: Fermi GBM Final Real-time Localization
  59. GRB 260618A: Fermi GBM Observation
  60. MASS-Cube (GRID 2.0) detection of GRB 260616B
  61. Fermi GBM trigger 804010507/260624677 is not a GRB
  62. Konus-Wind detection of GRB 260618B
  63. GRB 260624A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  64. GRB 260624A: Fermi GBM Final Real-time Localization
  65. GRB 260617A: Glowbug gamma-ray detection of a short burst
  66. GRB 260623A: Fermi GBM Final Real-time Localization
  67. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  68. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  69. GRB 260618B: LCO optical observations
  70. EP260618a: JinShan optical observations
  71. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  72. GRB 260618B: Fermi GBM Observation
  73. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  74. GRB 260604B: 239Alferov CubeSat detection
  75. GRB 260604A: 239Alferov CubeSat detection
  76. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  77. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  78. GRB 260618B: SVOM/VT optical candidate
  79. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  80. Konus-Wind detection of GRB 260617A
  81. GRB 260616B: AstroSat CZTI detection
  82. GRB 260616A: AstroSat CZTI detection
  83. GRB 260616A: SVOM/GRM observation
  84. EP260618a: OHP/T193 optical observations
  85. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  86. EP260618a: EP-FXT follow-up observation
  87. EP260618a: LCO optical counterpart confirmation
  88. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  89. EP260618a: COLIBRÍ optical counterpart candidate
  90. GRB 260616A: NuSTAR detection of prompt emission
  91. GRB 260614B: NuSTAR detection of prompt emission
  92. GRB 260618B: Fermi-LAT detection
  93. IPN triangulation of GRB 260617A (short)
  94. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  95. GRB 260616A: Insight-HXMT detection
  96. GRB 260618B: Fermi GBM Final Real-time Localization
  97. EP260618a: EP-WXT detection of an X-ray transient
  98. GRB 260610B: AbAO optical observations
  99. GRB 260506B: cubesat Avion detection
  100. GRB 260618A: Fermi GBM Final Real-time Localization

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