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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 210410A: Swift-BAT refined analysis
  2. GRB 210411B: Fermi GBM Final Real-time Localization
  3. Fermi GRB 210411A: Global MASTER-Net observations report
  4. GRB 210410A: Swift-XRT refined Analysis
  5. GRB 210411A: Fermi GBM Final Real-time Localization
  6. GRB 210410A: Fermi GBM detection
  7. GRB 210410A: Swift/UVOT Upper Limits
  8. GRB210410A: Joint inspection of RATIR and D50 data
  9. GRB 210406A: Swift-XRT observations
  10. GRB 210410A: RATIR Optical and NIR Observations
  11. GRB 210409A: GECAM detection
  12. GRB 210410A: AGILE detection of a burst
  13. GRB 210410A: Fermi-LAT detection
  14. GRB210410A: Candidate optical afterglow by Ondrejov D50
  15. Fermi GRB 210410A: Global MASTER-Net observations report
  16. GRB 210410A: Swift XRT localization
  17. GRB 210410A: Fermi GBM Final Real-time Localization
  18. Swift Triggers 1042031 and 1042032 are not astrophysical events
  19. GRB 210406A: Mondy optical afterglow candidate
  20. GRB 210406A: Swift ToO observations
  21. GRB 210406B: Fermi GBM detection
  22. Konus-Wind detection of GRB 210406A
  23. GRB 210406A: Fermi GBM detection
  24. GRB 210406A: Mondy optical upper limit
  25. GRB 210406A: Konkoly Obs. optical upper limit
  26. GRB 210406A: BOOTES-4/MET optical upper limit
  27. GRB 210406A: A long GRB detected by INTEGRAL
  28. Integral GRB210406.72: Global MASTER-Net observations report
  29. GRB 210402A: MASTER prompt and follow up optical observation
  30. GRB 210402A: Swift/UVOT Upper Limits
  31. GRB 210402A: Fermi GBM detection
  32. GRB 210402A: Further NOT optical observations
  33. GRB 210402A: Swift-BAT refined analysis
  34. GRB 210404.141: DDOTI Upper Limits
  35. GRB 210207B: Prompt and very late time observations with HCT.
  36. GRB 210401A: GECAM detection
  37. GRB 210402A: NOT optical afterglow candidate
  38. Fermi trigger No 639199407: Global MASTER-Net observations report
  39. GRB 210402A: BOOTES-network early optical upper limit
  40. GRB 210403A: Swift-BAT refined analysis
  41. GRB 210402A: LBT observations
  42. GRB 210402A: DDOTI Upper Limits
  43. Swift GRB210403.35: Global MASTER-Net observations report
  44. GRB 210402A: Swift-XRT refined Analysis
  45. GRB 210330A: AstroSat CZTI detection
  46. GRB 210403A: Swift detection of a burst
  47. GRB 210402A: Montarrenti Observatory upper limit
  48. GRB 210328A: AstroSat CZTI detection
  49. GRB 210402A: NOT optical upper limits
  50. Konus-Wind detection of GRB 210401A
  51. GRB 210402A: Swift detection of a burst
  52. Fermi trigger No 639093861: Global MASTER-Net observations report
  53. Swift GRB210402.92: Global MASTER-Net observations report
  54. Fermi GRB 210401A: Global MASTER-Net observations report
  55. GRB 210401A: Fermi GBM Final Real-time Localization
  56. GRB 210330A: MASTER optical observation
  57. GRB 210328A: GECAM detection
  58. GRB 210330A: GECAM detection
  59. GRB 210324A: AstroSat CZTI detection
  60. GRB 210324C: AstroSat CZTI detection
  61. GRB 210328A: BALROG localization (Fermi Trigger / GRB 210328865)
  62. GRB 210328A: Fermi GBM Final Real-time Localization
  63. GRB 210326A: Insight-HXMT/HE detection
  64. GRB 210326A: Fermi GBM Final Localization
  65. Fermi trigger No 638414549: Global MASTER-Net observations report
  66. Konus-Wind detection of GRB 210324C
  67. IPN triangulation of GRB 210324C
  68. GRB 210323A: Insight-HXMT/HE detection
  69. GRB 210321A: OSN Upper Limit
  70. GRB 210323A: MASTER optical observation
  71. Fermi GRB 210324C: Global MASTER-Net observations report
  72. Fermi GRB 210324B: Global MASTER-Net observations report
  73. GRB 210323A: Swift-BAT refined analysis
  74. GRB 210323A: Gemini-North Optical Source Detection
  75. GRB 210324C: BALROG localization (Fermi Trigger 638308803 / GRB 210324833)
  76. GRB 210324C: Fermi GBM Final Real-time Localization
  77. Short GRB 210323A: GTC Observations
  78. GRB 210312B: OSN Afterglow Observations
  79. GRB 210324B: Fermi GBM Final Real-time Localization
  80. GRB 210323B: Swift ToO observations
  81. Konus-Wind detection of GRB 210323A (short)
  82. GRB 210323A: Swift/UVOT Upper Limits
  83. GRB 210323A: Classification and redshift estimation
  84. GRB 210323A: Kitab optical upper limit
  85. GRB 210323A: Fermi GBM detection
  86. GRB 210323A: Mondy optical observations, counterpart detection
  87. GRB 210324A: Fermi GBM Final Real-time Localization
  88. GRB 210318A: Swift/UVOT Upper Limits
  89. GRB 210323A: Swift-XRT refined Analysis
  90. GRB 210323A: Enhanced Swift-XRT position
  91. GRB 210323A: NOT optical afterglow candidate
  92. Swift GRB 210323A: Global MASTER-Net observations report
  93. GRB 210323B: Swift/BAT-GUANO detection and possible arcminute localization
  94. GRB 210323A: Nanshan/NEXT optical upper limit
  95. GRB 210323A: Swift detection of a short burst
  96. Fermi GBM trigger 637977270/210320996 is not a GRB
  97. GRB 210321A: Swift/UVOT Detection
  98. Konus-Wind detection of GRB 210321A
  99. GRB 210318B: Swift/UVOT Upper Limits
  100. GRB 210321A: DDOTI Position Correction

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