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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"

11533 results found.

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

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