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

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
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