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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 210411C: LCO Optical Afterglow Candidate
  2. Fermi GRB 210411B: Global MASTER-Net observations report
  3. GRB 210411C: Enhanced Swift-XRT position
  4. GRB 210406A: 10.4m GTC follow-up observation
  5. GRB 210410A: AGILE/MCAL analysis
  6. Konus-Wind detection of GRB 210410A
  7. GRB 210411D: BALROG localization (Fermi Trigger 639851475 / GRB 210411688)
  8. GRB 210411D: Fermi GBM Final Real-time Localization
  9. GRB 210411C: Swift detection of a burst with an optical counterpart
  10. GRB 210410A: Swift-BAT refined analysis
  11. GRB 210411B: Fermi GBM Final Real-time Localization
  12. Fermi GRB 210411A: Global MASTER-Net observations report
  13. GRB 210410A: Swift-XRT refined Analysis
  14. GRB 210411A: Fermi GBM Final Real-time Localization
  15. GRB 210410A: Fermi GBM detection
  16. GRB 210410A: Swift/UVOT Upper Limits
  17. GRB210410A: Joint inspection of RATIR and D50 data
  18. GRB 210406A: Swift-XRT observations
  19. GRB 210410A: RATIR Optical and NIR Observations
  20. GRB 210409A: GECAM detection
  21. GRB 210410A: AGILE detection of a burst
  22. GRB 210410A: Fermi-LAT detection
  23. GRB210410A: Candidate optical afterglow by Ondrejov D50
  24. Fermi GRB 210410A: Global MASTER-Net observations report
  25. GRB 210410A: Swift XRT localization
  26. GRB 210410A: Fermi GBM Final Real-time Localization
  27. Swift Triggers 1042031 and 1042032 are not astrophysical events
  28. GRB 210406A: Mondy optical afterglow candidate
  29. GRB 210406A: Swift ToO observations
  30. GRB 210406B: Fermi GBM detection
  31. Konus-Wind detection of GRB 210406A
  32. GRB 210406A: Fermi GBM detection
  33. GRB 210406A: Mondy optical upper limit
  34. GRB 210406A: Konkoly Obs. optical upper limit
  35. GRB 210406A: BOOTES-4/MET optical upper limit
  36. GRB 210406A: A long GRB detected by INTEGRAL
  37. Integral GRB210406.72: Global MASTER-Net observations report
  38. GRB 210402A: MASTER prompt and follow up optical observation
  39. GRB 210402A: Swift/UVOT Upper Limits
  40. GRB 210402A: Fermi GBM detection
  41. GRB 210402A: Further NOT optical observations
  42. GRB 210402A: Swift-BAT refined analysis
  43. GRB 210404.141: DDOTI Upper Limits
  44. GRB 210207B: Prompt and very late time observations with HCT.
  45. GRB 210401A: GECAM detection
  46. GRB 210402A: NOT optical afterglow candidate
  47. Fermi trigger No 639199407: Global MASTER-Net observations report
  48. GRB 210402A: BOOTES-network early optical upper limit
  49. GRB 210403A: Swift-BAT refined analysis
  50. GRB 210402A: LBT observations
  51. GRB 210402A: DDOTI Upper Limits
  52. Swift GRB210403.35: Global MASTER-Net observations report
  53. GRB 210402A: Swift-XRT refined Analysis
  54. GRB 210330A: AstroSat CZTI detection
  55. GRB 210403A: Swift detection of a burst
  56. GRB 210402A: Montarrenti Observatory upper limit
  57. GRB 210328A: AstroSat CZTI detection
  58. GRB 210402A: NOT optical upper limits
  59. Konus-Wind detection of GRB 210401A
  60. GRB 210402A: Swift detection of a burst
  61. Fermi trigger No 639093861: Global MASTER-Net observations report
  62. Swift GRB210402.92: Global MASTER-Net observations report
  63. Fermi GRB 210401A: Global MASTER-Net observations report
  64. GRB 210401A: Fermi GBM Final Real-time Localization
  65. GRB 210330A: MASTER optical observation
  66. GRB 210328A: GECAM detection
  67. GRB 210330A: GECAM detection
  68. GRB 210324A: AstroSat CZTI detection
  69. GRB 210324C: AstroSat CZTI detection
  70. GRB 210328A: BALROG localization (Fermi Trigger / GRB 210328865)
  71. GRB 210328A: Fermi GBM Final Real-time Localization
  72. GRB 210326A: Insight-HXMT/HE detection
  73. GRB 210326A: Fermi GBM Final Localization
  74. Fermi trigger No 638414549: Global MASTER-Net observations report
  75. Konus-Wind detection of GRB 210324C
  76. IPN triangulation of GRB 210324C
  77. GRB 210323A: Insight-HXMT/HE detection
  78. GRB 210321A: OSN Upper Limit
  79. GRB 210323A: MASTER optical observation
  80. Fermi GRB 210324C: Global MASTER-Net observations report
  81. Fermi GRB 210324B: Global MASTER-Net observations report
  82. GRB 210323A: Swift-BAT refined analysis
  83. GRB 210323A: Gemini-North Optical Source Detection
  84. GRB 210324C: BALROG localization (Fermi Trigger 638308803 / GRB 210324833)
  85. GRB 210324C: Fermi GBM Final Real-time Localization
  86. Short GRB 210323A: GTC Observations
  87. GRB 210312B: OSN Afterglow Observations
  88. GRB 210324B: Fermi GBM Final Real-time Localization
  89. GRB 210323B: Swift ToO observations
  90. Konus-Wind detection of GRB 210323A (short)
  91. GRB 210323A: Swift/UVOT Upper Limits
  92. GRB 210323A: Classification and redshift estimation
  93. GRB 210323A: Kitab optical upper limit
  94. GRB 210323A: Fermi GBM detection
  95. GRB 210323A: Mondy optical observations, counterpart detection
  96. GRB 210324A: Fermi GBM Final Real-time Localization
  97. GRB 210318A: Swift/UVOT Upper Limits
  98. GRB 210323A: Swift-XRT refined Analysis
  99. GRB 210323A: Enhanced Swift-XRT position
  100. GRB 210323A: NOT optical afterglow candidate

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