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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 210421A: Swift-BAT refined analysis
  2. GRB 210421B: Swift-XRT observations
  3. GRB 210421B: AstroSat CZTI detection
  4. GRB 210420B: continued Tautenburg observations
  5. GRB 210421A: GECAM detection
  6. GRB 210421B: AstroSat CZTI detection
  7. Swift GRB210422.74: Global MASTER-Net observations report
  8. GRB 210422A: Swift detection of a burst
  9. GRB 210421A: Swift/UVOT Upper Limits
  10. GRB 210420B: Correction to AST3-3 YaoAn magnitude
  11. GRB 210420B: follow-up photometry of the optical afterglow at Konkoly
  12. GRB 210421A: MITSuME Akeno optical upper limits
  13. GRB 210419B: AstroSat CZTI detection
  14. Fermi Gamma-ray Burst Monitor trigger 210421C is not a GRB
  15. GRB 210420B: Swift-BAT refined analysis
  16. GRB 210421B: Swift ToO observations
  17. GRB 210421B: Swift/BAT-GUANO detection and arcminute localization
  18. GRB 210420B: Swift-XRT refined Analysis
  19. GRB 210421A: Swift-XRT refined Analysis
  20. GRB 210421B: Correction of GRB Type to "Likely Long GRB"
  21. Fermi GRB 210421C: Global MASTER-Net observations report
  22. GRB 210420B: Montarrenti Observatory follow-up observations
  23. GRB 210421C: Fermi GBM Final Real-time Localization
  24. GRB 210421B: Fermi GBM Final Localization
  25. Fermi trigger No 640695289: Global MASTER-Net observations report
  26. GRB 210419C: Swift/UVOT Upper Limits
  27. GRB 210420B: Correction to DDOTI Magnitude
  28. GRB 210420B: Ondrejov D50 optical afterglow detection
  29. GRB 210421A: Enhanced Swift-XRT position
  30. GRB 210420B: RATIR Optical and NIR Observations
  31. GRB 210420B: Tautenburg observations
  32. GRB 210420B: Swift/UVOT Detection
  33. GRB 210420B: KAIT Optical Observations
  34. GRB 210413B: MITSuME Okayama optical upper limits
  35. GRB 210419C: MITSuME Akeno optical upper limits
  36. GRB 210420B: DDOTI Detection of the Afterglow
  37. GRB 210421A: DDOTI Upper Limit
  38. GRB 210419C: Swift-BAT refined analysis
  39. Fermi GRB 210420A: Global MASTER-Net observations report
  40. GRB 210420B: update on the BAT trigger time
  41. GRB 210420B: Redshift from GTC
  42. GRB 210420B: Multiband photometry from NOT
  43. GRB 210420B: Montarrenti Observatory optical afterglow detection
  44. Swift GRB 210421A: Global MASTER-Net observations report
  45. GRB 210421A: Swift detection of a burst
  46. GRB 210420B: AST3-3 YaoAn Optical Observation
  47. GRB 210420B: BOOTES-4/MET optical afterglow detection
  48. GRB 210420B: Optical observations
  49. GRB 210420B: MASTER optical counterpart detection
  50. GRB 210420B: Swift detection of a burst
  51. GRB 210419C: RATIR Optical and NIR Upper Limits
  52. GRB 210419C: Montarrenti Observatory Upper Limit
  53. GRB 210419A: Swift/UVOT Upper Limits
  54. GRB 210419C: KAIT Optical Upper Limit
  55. GRB 210419C: Enhanced Swift-XRT position
  56. GRB 210419A: Swift-BAT refined analysis
  57. GRB 210420A: Fermi GBM Final Real-time Localization
  58. Swift GRB210419.98: Global MASTER-Net observations report
  59. GRB 210419A: Swift-XRT refined Analysis
  60. GRB 210419C: Swift detection of a burst
  61. Fermi GRB 210419B: Global MASTER-Net observations report
  62. Swift GRB 210419A: Global MASTER-Net observations report
  63. GRB 210419B: Fermi GBM Final Real-time Localization
  64. GRB 210419A: Enhanced Swift-XRT position
  65. GRB 210419A: LCO Optical Upper Limit
  66. GRB 210419A: Swift detection of a burst
  67. GRB 210413B: Swift-XRT observations
  68. Fermi GBM trigger 640353092/210417494 is not a GRB
  69. GRB 210413B: LOAO optical upper limit
  70. Fermi Gamma-ray Burst Monitor trigger 640303939/210416925 is not a GRB
  71. GRB 210411C: A very significant early X-ray afterglow
  72. IceCube Alert 210416.09: Global MASTER-Net observations report
  73. GRB 210413B: Swift ToO observations
  74. IceCubeCascade-210416a: Kanata Optical Imaging of 3C 279
  75. GRB 210413B: Swift/BAT detection and probable localization of a short burst
  76. GRB 210411B: AstroSat CZTI detection
  77. GRB 210410A: AstroSat CZTI detection
  78. GRB 210410A: A twin of short GRB 090510 with complementary observations
  79. Fermi GRB 210415A: Global MASTER-Net observations report
  80. GRB 210415A: Fermi GBM Final Real-time Localization
  81. GRB 210413A: GECAM detection
  82. GRB 210410A: Swift/UVOT Upper Limits (revision)
  83. GRB 210411C: Swift/UVOT Detection
  84. GRB 210411C: Swift-BAT refined analysis
  85. GRB 210411C: Chilescope optical observations
  86. GRB 210411C: ePESSTO+ NTT optical observations
  87. GRB 210411C: Swift-XRT refined Analysis
  88. GRB 210411C: VLT/X-shooter redshift
  89. GRB 210410A: MITSuME Akeno optical upper limits
  90. Swift GRB 210411C: Global MASTER-Net observations report
  91. GRB 210411C: BOOTES-4/MET optical upper limit
  92. GRB 210411C: LCO Optical Afterglow Candidate
  93. Fermi GRB 210411B: Global MASTER-Net observations report
  94. GRB 210411C: Enhanced Swift-XRT position
  95. GRB 210406A: 10.4m GTC follow-up observation
  96. GRB 210410A: AGILE/MCAL analysis
  97. Konus-Wind detection of GRB 210410A
  98. GRB 210411D: BALROG localization (Fermi Trigger 639851475 / GRB 210411688)
  99. GRB 210411D: Fermi GBM Final Real-time Localization
  100. GRB 210411C: Swift detection of a burst with an optical counterpart

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