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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"

11511 results found.

  1. GRB 260705B: SVOM/GRM observation
  2. GRB 260708A: Fermi-GBM detection
  3. GRB 260706A: Further EP-FXT follow-up observation
  4. GRB 260706A: SVOM/VT optical upper limits
  5. Fermi GBM trigger 805087514/260707142 (GRB 260707A) is not a GRB
  6. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  7. GRB 260705C: Glowbug gamma-ray detection of a short burst
  8. GRB 260706A: SVOM/ECLAIRs refined analysis
  9. GRB 260706A: SVOM/GRM observation
  10. GRB 260706A: REM optical/NIR observations
  11. GRB 260706A: LCO optical upper limit
  12. GRB 260706A: EP-FXT follow-up observation
  13. GRB 260707A: Fermi GBM Final Real-time Localization
  14. GRB 260706A: Fermi GBM Observation
  15. GRB 260706A: SVOM detection of a burst
  16. GRB 260706A: Fermi GBM Final Real-time Localization
  17. GRB 260705C: Fermi GBM Final Localization
  18. GRB 260705B: Fermi GBM Final Real-time Localization
  19. Fermi GBM Sub-Threshold Detection of GRB 260705A
  20. GRB 260629A: SVOM/GRM observation of a short burst
  21. GRB 260629A: GECAM-A observation of a short burst
  22. IceCube-260704A - IceCube observation of a high-energy neutrino candidate track-like event
  23. GRB 260629A: AstroSat CZTI detection
  24. GRB 260703B: Fermi GBM Final Localization
  25. Fermi trigger No 804738310: Global MASTER-Net observations report
  26. Fermi GRB 260703A: Global MASTER-Net observations report
  27. GRB 260703A: Fermi GBM Final Localization
  28. GRB 260610B: VLA detection
  29. GRB 260623A: Glowbug gamma-ray detection
  30. GRB 260614B: ATCA Radio Upper Limits
  31. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  32. Fermi trigger No 804552016: Global MASTER-Net observations report
  33. GRB 260701A: Fermi GBM Final Real-time Localization
  34. Fermi GBM trigger 804552016/260630945 is not a GRB
  35. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  36. GRB 260629A: Fermi GBM Final Real-time Localization
  37. Fermi GRB 260628A: Global MASTER-Net observations report
  38. GRB 260628A: Fermi GBM Final Real-time Localization
  39. GRB 260618A: Fermi GBM Observation
  40. MASS-Cube (GRID 2.0) detection of GRB 260616B
  41. Fermi GBM trigger 804010507/260624677 is not a GRB
  42. Konus-Wind detection of GRB 260618B
  43. GRB 260624A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  44. GRB 260624A: Fermi GBM Final Real-time Localization
  45. GRB 260617A: Glowbug gamma-ray detection of a short burst
  46. GRB 260623A: Fermi GBM Final Real-time Localization
  47. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  48. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  49. GRB 260618B: LCO optical observations
  50. EP260618a: JinShan optical observations
  51. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  52. GRB 260618B: Fermi GBM Observation
  53. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  54. GRB 260604B: 239Alferov CubeSat detection
  55. GRB 260604A: 239Alferov CubeSat detection
  56. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  57. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  58. GRB 260618B: SVOM/VT optical candidate
  59. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  60. Konus-Wind detection of GRB 260617A
  61. GRB 260616B: AstroSat CZTI detection
  62. GRB 260616A: AstroSat CZTI detection
  63. GRB 260616A: SVOM/GRM observation
  64. EP260618a: OHP/T193 optical observations
  65. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  66. EP260618a: EP-FXT follow-up observation
  67. EP260618a: LCO optical counterpart confirmation
  68. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  69. EP260618a: COLIBRÍ optical counterpart candidate
  70. GRB 260616A: NuSTAR detection of prompt emission
  71. GRB 260614B: NuSTAR detection of prompt emission
  72. GRB 260618B: Fermi-LAT detection
  73. IPN triangulation of GRB 260617A (short)
  74. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  75. GRB 260616A: Insight-HXMT detection
  76. GRB 260618B: Fermi GBM Final Real-time Localization
  77. EP260618a: EP-WXT detection of an X-ray transient
  78. GRB 260610B: AbAO optical observations
  79. GRB 260506B: cubesat Avion detection
  80. GRB 260618A: Fermi GBM Final Real-time Localization
  81. GRB 260617A: Fermi GBM Detection
  82. GRB 260616A: Fermi GBM Observation
  83. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  84. GRB 260617A: Fermi GBM Final Real-time Localization
  85. Konus-Wind detection of GRB 260616B/EP260616a
  86. Konus-Wind detection of GRB 260616A
  87. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  88. GRB 260616A: GECAM-B observation
  89. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  90. GRB 260429A: cubesat Avion detection
  91. GRB 260616A: Fermi-LAT detection
  92. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  93. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  94. GRB 260614A: AstroSat CZTI detection
  95. EP260616a: EP-WXT detection of a fast X-ray transient
  96. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  97. GRB 260616B: Fermi GBM Detection
  98. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  99. GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
  100. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)

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