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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 260704A: NOT optical upper limits
  2. GRB 260705C: Fermi GBM Final Localization
  3. GRB 260705B: Fermi GBM Final Real-time Localization
  4. Fermi GBM Sub-Threshold Detection of GRB 260705A
  5. GRB 260705A: SVOM detection of a burst
  6. GRB 260704A: EP-FXT follow-up observation
  7. GRB 260629A: SVOM/GRM observation of a short burst
  8. GRB 260629A: GECAM-A observation of a short burst
  9. IceCube-260704A - IceCube observation of a high-energy neutrino candidate track-like event
  10. GRB 260629A: AstroSat CZTI detection
  11. EP260703a: EP-FXT follow-up observation
  12. GRB 260704A: SVOM detection of a possible GRB
  13. GRB 260703B: Fermi GBM Final Localization
  14. EP260703a: EP-WXT detection of a fast X-ray transient
  15. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  16. Fermi trigger No 804738310: Global MASTER-Net observations report
  17. Fermi GRB 260703A: Global MASTER-Net observations report
  18. GRB 260703A: Fermi GBM Final Localization
  19. GRB 260610B: VLA detection
  20. GRB 260623A: Glowbug gamma-ray detection
  21. GRB 260614B: ATCA Radio Upper Limits
  22. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  23. Fermi trigger No 804552016: Global MASTER-Net observations report
  24. GRB 260701A: Fermi GBM Final Real-time Localization
  25. Fermi GBM trigger 804552016/260630945 is not a GRB
  26. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  27. EP260628a: EP-FXT follow-up observation
  28. GRB 260629A: Fermi GBM Final Real-time Localization
  29. Fermi GRB 260628A: Global MASTER-Net observations report
  30. EP260628a: EP-WXT detection of a fast X-ray transient
  31. GRB 260628A: Fermi GBM Final Real-time Localization
  32. The EP-WXT trigger 01709272671 is likely a flaring star
  33. EP260626a: further Liverpool Telescope optical upper limits
  34. EP260626a: EP-FXT follow-up observation
  35. EP260626a: COLIBRÍ optical upper limit
  36. EP260626a: Liverpool Telescope upper limits
  37. EP260626a: EP-WXT detection of a fast X-ray transient
  38. Konus-Wind detection of GRB 260623B / EP260623a
  39. EP260623a: TNG NIR afterglow detection
  40. GRB 260618A: Fermi GBM Observation
  41. MASS-Cube (GRID 2.0) detection of GRB 260616B
  42. EP260623a: FTW optical and NIR observations
  43. GRB 260619A: SVOM/ECLAIRs refined analysis
  44. EP260623a: Liverpool Telescope optical observations
  45. Fermi GBM trigger 804010507/260624677 is not a GRB
  46. Konus-Wind detection of GRB 260618B
  47. GRB 260624A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  48. GRB 260624A: Fermi GBM Final Real-time Localization
  49. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  50. EP260623a: WINTER J-band observations
  51. GRB 260617A: Glowbug gamma-ray detection of a short burst
  52. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  53. IPN triangulation of GRB 260605A
  54. EP260623a: Optical follow-up observations with Kinder
  55. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  56. GRB 260623A: Fermi GBM Final Real-time Localization
  57. EP260623a: SVOM/VT optical observations
  58. EP260623a: TRT optical observations
  59. EP260623a: REM optical/NIR afterglow detection
  60. EP 260623a: COLIBRÍ optical observations
  61. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  62. EP260623a: OSIRIS+/GTC redshift z = 0.703
  63. EP260623a: Las Cumbres discovery of the optical counterpart
  64. EP260623a: Einstein Probe detection of an X-ray transient
  65. GRB 260614B: EP-FXT follow-up observation
  66. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  67. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  68. EP260618a: Liverpool Telescope optical observations
  69. GRB 260619A: NOT optical observations
  70. GRB 260618B: LCO optical observations
  71. The EP-WXT trigger 01709271197 is likely a flaring star
  72. EP260618a: JinShan optical observations
  73. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  74. GRB 260618B: Fermi GBM Observation
  75. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  76. GRB 260619A: TRT optical counterpart confirmation
  77. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  78. GRB 260604B: 239Alferov CubeSat detection
  79. GRB 260604A: 239Alferov CubeSat detection
  80. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  81. GRB 260619A: SVOM/VT optical counterpart confirmation
  82. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  83. GRB 260618B: SVOM/VT optical candidate
  84. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  85. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  86. Konus-Wind detection of GRB 260617A
  87. GRB 260616B: AstroSat CZTI detection
  88. GRB 260616A: AstroSat CZTI detection
  89. GRB 260616A: SVOM/GRM observation
  90. EP260618a: OHP/T193 optical observations
  91. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  92. GRB 260619A: Kilonova-Catcher optical upper limit
  93. EP260618a: EP-FXT follow-up observation
  94. EP260618a: LCO optical counterpart confirmation
  95. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  96. EP260618a: COLIBRÍ optical counterpart candidate
  97. GRB 260616A: NuSTAR detection of prompt emission
  98. GRB 260614B: NuSTAR detection of prompt emission
  99. GRB 260619A: SVOM possible detection of a faint burst
  100. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube

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