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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 211102A: Fermi GBM Final Real-time Localization
  2. GRB 211024B: Optical afterglow observation by Ondrejov D50
  3. GRB 211024A: 1.3m DFOT observations
  4. Fermi GRB 211031A: Global MASTER-Net observations report
  5. GRB 211031A: Fermi GBM Final Real-time Localization
  6. IPN triangulation of GRB 211022A
  7. GRB 211023A: 1.3m DFOT Optical Observations
  8. Konus-Wind detection of GRB 211023A
  9. GRB 2121023B: 6 GHz VLA radio upper limit
  10. GRB 211023A: Terskol optical observations
  11. AMON NuEm-211020A: No Candidate Counterparts from Swift-XRT follow up observations
  12. GRB 211023A: continued Mondy optical observations
  13. GRB 211024A: Swift-XRT source 4 is not an afterglow.
  14. GRB 211023B: NUTTelA-TAO / BSTI Early Optical Limits (Preliminary)
  15. Fermi GRB 211027A: Global MASTER-Net observations report
  16. GRB 211024A: Possible afterglow candidate from GIT
  17. GRB 211024A: Swift-XRT observations
  18. GRB 211027A: Fermi GBM Final Real-time Localization
  19. GRB 211024A: Fermi GBM detection
  20. GRB 211018A: Swift-XRT observations
  21. GRB 211025A: Optical Afterglow Detection
  22. GRB211023A: optical afterglow detection from Konkoly Observatory
  23. GRB 211024A: Swift ToO observations
  24. GRB 211024A: Swift/BAT-GUANO detection and candidate arcminute localization of a short burst
  25. GRB 211024B: Swift/UVOT detection
  26. GRB 211023A: Mondy optical observations
  27. GRB 211023B: Mondy optical afterglow confirmation
  28. GRB 211023B: Gemini-North Optical Observations
  29. Swift GRB 211025A: Global MASTER-Net observations report
  30. GRB 211023B: LDT Optical Afterglow Detection
  31. IceCube-211023A: Upper limits from a search for additional neutrino events in IceCube
  32. Correction to GCN 30965: GRB 211023A: Fermi GBM detection
  33. GRB 211025A: Swift-BAT refined analysis
  34. GRB 211025A: Swift-XRT refined Analysis
  35. GRB 211024B: CAHA 2.2m Detection; ultra-long GRB?
  36. GRB 211024B: Swift-XRT refined Analysis
  37. IPN Triangulation of GRB 211019A
  38. Possible Short GRB 211023B: CAHA 2.2m Detection
  39. GRB 211025A: Swift/UVOT Detection
  40. GRB 211023A: 1.5m OSN optical observation
  41. GRB 211024B: Swift-BAT refined analysis
  42. GRB 210610B: Sintesz-Newton/CrAO optical observations
  43. GRB 211025A: Enhanced Swift-XRT position
  44. GRB 211025A: Swift detection of a burst
  45. GECAM detection of a short burst probably from SGR J1555.2-5402
  46. GRB 211024B: Nanshan/NEXT optical afterglow detection
  47. GRB 210919A: FORS2/VLT observations
  48. GRB 211023A: OAJ Bright Afterglow Confirmation
  49. Swift GRB 211024B: Global MASTER-Net observations report
  50. GRB 211024B: Swift detection of a burst
  51. GRB 211023B: Swift-BAT refined analysis
  52. Fermi-LAT Gamma-ray Observations of IceCube-211023A
  53. GRB 211023A: MASTER OT J045237.07+851925.2 - optical counterpart discovery
  54. GRB 211023B: BOOTES-4/MET and 1.5m OSN optical upper limit
  55. GRB 211023B: Swift/UVOT Detection
  56. GRB 211024A: GECAM detection
  57. GRB 211023B: RATIR Optical and NIR Upper Limits
  58. GRB 211023B: TSHAO optical observation
  59. IceCube-211023A: No neutrino counterpart detected with ANTARES
  60. Fermi GRB 211023A: Global MASTER-Net observations report
  61. GRB 211023A: AGILE detection
  62. GRB 211022A: AstroSat CZTI detection
  63. GRB 211023B: Swift-XRT refined Analysis
  64. GRB 211023B: Enhanced Swift-XRT position
  65. GRB 211023A: Fermi GBM detection
  66. Swift GRB 211023B: Global MASTER-Net observations report
  67. Fermi GRB 211024A: Global MASTER-Net observations report
  68. GRB 211024A: Fermi GBM Final Real-time Localization
  69. GRB 211023A: Fermi-LAT detection
  70. GRB 211023B: Swift detection of a possibly short burst with an optical counterpart
  71. IceCube Alert 211023.36: Global MASTER-Net observations report
  72. GRB 211023A: Fermi GBM Final Real-time Localization
  73. IceCube-211023A - IceCube observation of a high-energy neutrino candidate track-like event
  74. IPN Triangulation of GRB 210927B
  75. GRB 211022A: GECAM detection
  76. AMON IC_HAWC NuEm-211020A: No neutrino counterpart detected with ANTARES
  77. GRB 211018A: Swift ToO observations
  78. GRB 211021A: BALROG localization (Fermi Trigger 656506979 / GRB 211021460)
  79. Fermi trigger No 656506979: Global MASTER-Net observations report
  80. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-211020A
  81. BepiColombo MGNS joins the IPN
  82. Fermi trigger No 656268212: Global MASTER-Net observations report
  83. GRB 211018A: Fermi GBM observation
  84. GRB 211019A: Detection by GRBAlpha
  85. GRB 211018A: Detection by GRBAlpha
  86. Fermi GRB 211019A: Global MASTER-Net observations report
  87. GRB 211018A: Fermi-LAT detection
  88. GRB 211019A: BALROG localization (Fermi Trigger 656315976 / GRB 211019250)
  89. GRB 211019A: Fermi GBM Final Real-time Localization
  90. Fermi trigger No 656288898: Global MASTER-Net observations report
  91. Swift GRB211017.99: Global MASTER-Net observations report
  92. Integral GRB211016.42: Global MASTER-Net observations report
  93. IceCube-210922A: Hard X-ray flux limit for JCMT/SCUBA2 source from NuSTAR observations
  94. Swift trigger 1078701: MITSuME Akeno optical upper limits
  95. Fermi trigger No 655673024: Global MASTER-Net observations report
  96. GRB 210919A: LDT optical observations and candidate host galaxies
  97. IceCube-20210922A: No optical counterparts found by MITSuME observations
  98. Swift Trigger 1078701: Mondy, CrAO, AbAO observations, possible optical counterpart
  99. Fermi trigger No 655646385: Global MASTER-Net observations report
  100. Swift GRB211010.45: Global MASTER-Net observations report

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