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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 200826A: AGILE detection
  2. GRB 200826A: AstroSat CZTI detection
  3. GRB 200826A: Fermi GBM observation
  4. GRB 200826A: BALROG localization (Fermi Trigger 620108997 / GRB 200826187)
  5. Fermi GRB 200826A: Global MASTER-Net observations report
  6. GRB 200826A: Fermi GBM Final Real-time Localization
  7. GRB 200824A: Fermi GBM Final Real-time Localization
  8. Swift Trigger 992444 is due to detector noise
  9. GRB 200819A: Swift/UVOT Upper Limits
  10. Swift GRB200821.55: Global MASTER-Net observations report
  11. IceCube-200806A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  12. Swift Trigger 992444: a possible GRB 200821A
  13. Konus-Wind observation of GRB 200815A
  14. GRB 200819A: Swift-BAT refined analysis
  15. GRB 200815A: MASTER optical observations
  16. IPN triangulation of GRB 200815A (short)
  17. GRB 200819A: Optical Observations from HCT
  18. GRB 200819A: Swift-XRT refined Analysis
  19. GRB 200819A: MITSuME Ishigaki optical upper limits
  20. GRB 200729A: Lowell Discovery Telescope observations
  21. GRB 200819A: MITSuME Akeno optical upper limits
  22. Baksan Neutrino Observatory Alert 200819.88: Global MASTER-Net observations report
  23. GRB 200819A / Swift J0125.7+6303: Ondrejov Perek-2m optical limit
  24. GRB 200819A: Kitab, TSHAO optical upper limit
  25. GRB 200819A: Enhanced Swift-XRT position
  26. Swift GRB 200819A: Global MASTER-Net observations report
  27. GRB 200819A: Swift detection of a burst
  28. Baksan Neutrino Observatory Alert 200819.09: Global MASTER-Net observations report
  29. GRB 200818A: Fermi GBM Final Localization
  30. Fermi trigger No 619487843: Global MASTER-Net observations report
  31. Swift Trigger 990358 is due to detector noise
  32. Swift Trigger 989458 is due to detector noise
  33. HAWC-200814A: Retraction of burst alert
  34. Fermi GRB 200817A: Global MASTER-Net observations report
  35. GRB 200815A: CALET Gamma-Ray Burst Monitor detection of a short burst
  36. GRB 200817A: Fermi GBM Final Real-time Localization
  37. Swift trigger 990358 is not an astrophysical source
  38. Swift GRB200816.17: Global MASTER-Net observations report
  39. Fermi trigger No 619270776: Global MASTER-Net observations report
  40. Swift trigger 989458 is likely not an astrophysical source
  41. HAWC alert 200815.26: MASTER optical observations
  42. Alert from the HAWC Burst Monitor HAWC-200814A
  43. IceCube200806A: No significant detection in HAWC
  44. GRB 200811A: Fermi GBM Final Real-time Localization
  45. GRB 200811A: BALROG localization (Fermi Trigger 618851447 / GRB 200811632)
  46. GRB 200809B: Fermi GBM detection
  47. Fermi GRB 200809B: Global MASTER-Net observations report
  48. GRB 200809B: BOOTES-3/YA optical upper limit
  49. GRB 200809B: Swift-XRT afterglow detection
  50. GRB 200809B: MAXI/GSC detection
  51. GRB 200809B: Swift ToO observations
  52. GRB 200809B: AstroSat CZTI detection
  53. GRB 200809B: Swift/BAT-GUANO detection and arcminute localization
  54. GRB 200809B: Fermi GBM Final Real-time Localization
  55. GRB 200808A: AGILE detection
  56. GRB 200806A: CALET Gamma-Ray Burst Monitor detection
  57. Fermi trigger No 618642276: Global MASTER-Net observations report
  58. GRB 200809A: Fermi GBM Final Real-time Localization
  59. Fermi GRB 200808A: Global MASTER-Net observations report
  60. GRB 200808A: Fermi GBM Final Real-time Localization
  61. GRB 200806A: Nanshan/NEXT optical upper limit
  62. IPN triangulation of GRB 200805A (short)
  63. GRB 200806A: CAHA optical afterglow confirmation
  64. GRB 200803A: Chilescope optical upper limit
  65. IceCube-200806A: Upper limits from a search for additional neutrino events in IceCube
  66. GRB 200806A: VIRT optical observations
  67. GRB 200806A: Swift-BAT refined analysis
  68. GRB 200806A: Swift/UVOT Possible Detection
  69. GRB 200806A: Swift-XRT refined Analysis
  70. Fermi-LAT Gamma-ray Observations of IceCube-200806A
  71. CGBM-SPI-ACS triangulation of short GRB 200805A
  72. GRB 200806A: AbAO optical upper limit
  73. GRB 200805A: CALET Gamma-Ray Burst Monitor detection of a short burst
  74. GRB 200806A: AstroSat CZTI detection
  75. GRB 200806A: MITSuME Akeno optical upper limits
  76. GRB 200806A: Enhanced Swift-XRT position
  77. IceCube-200806A: Upper limits from Fermi-GBM Observations
  78. Swift GRB 200806A: Global MASTER-Net observations report
  79. GRB 200806A: Swift detection of a burst
  80. IceCube-200806A: IceCube observation of a high-energy neutrino candidate event
  81. IceCube Alert 200806.58: Global MASTER-Net observations report
  82. GRB 200803B: MASTER possibly OT discovery
  83. GRB 200803A: AstroSat CZTI detection
  84. GRB 200803A: Fermi GBM detection
  85. GRB 200803A: Swift-XRT afterglow detection
  86. Fermi GRB 200803B: Global MASTER-Net observations report
  87. GRB 200803A: Fermi-LAT detection
  88. GRB 200803A: MASTER optical counterpart discovery
  89. GRB 200803B: Fermi GBM Final Real-time Localization
  90. GRB 200803A: Tiled Swift observations
  91. LAT GRB200803.15: Global MASTER-Net observations report
  92. Fermi GRB 200803A: Global MASTER-Net observations report
  93. GRB 200801B: AstroSat CZTI detection
  94. GRB 200803A: Fermi GBM Final Real-time Localization
  95. Fermi GRB 200801B: Global MASTER-Net observations report
  96. Fermi GRB 200802A: Global MASTER-Net observations report
  97. AX J1846.4-0258: Swift-BAT refined analysis
  98. Konus-Wind detection of GRB 200729A
  99. GRB 200802A: BALROG localization (Fermi Trigger 618061611 / GRB 200802491)
  100. GRB 200802A: Fermi GBM Final Real-time Localization

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