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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. IceCube-211023A: Upper limits from a search for additional neutrino events in IceCube
  2. Correction to GCN 30965: GRB 211023A: Fermi GBM detection
  3. GRB 211025A: Swift-BAT refined analysis
  4. GRB 211025A: Swift-XRT refined Analysis
  5. GRB 211024B: CAHA 2.2m Detection; ultra-long GRB?
  6. GRB 211024B: Swift-XRT refined Analysis
  7. IPN Triangulation of GRB 211019A
  8. Possible Short GRB 211023B: CAHA 2.2m Detection
  9. GRB 211025A: Swift/UVOT Detection
  10. GRB 211023A: 1.5m OSN optical observation
  11. GRB 211024B: Swift-BAT refined analysis
  12. GRB 210610B: Sintesz-Newton/CrAO optical observations
  13. GRB 211025A: Enhanced Swift-XRT position
  14. GRB 211025A: Swift detection of a burst
  15. GECAM detection of a short burst probably from SGR J1555.2-5402
  16. GRB 211024B: Nanshan/NEXT optical afterglow detection
  17. GRB 210919A: FORS2/VLT observations
  18. GRB 211023A: OAJ Bright Afterglow Confirmation
  19. Swift GRB 211024B: Global MASTER-Net observations report
  20. GRB 211024B: Swift detection of a burst
  21. GRB 211023B: Swift-BAT refined analysis
  22. Fermi-LAT Gamma-ray Observations of IceCube-211023A
  23. GRB 211023A: MASTER OT J045237.07+851925.2 - optical counterpart discovery
  24. GRB 211023B: BOOTES-4/MET and 1.5m OSN optical upper limit
  25. GRB 211023B: Swift/UVOT Detection
  26. GRB 211024A: GECAM detection
  27. GRB 211023B: RATIR Optical and NIR Upper Limits
  28. GRB 211023B: TSHAO optical observation
  29. IceCube-211023A: No neutrino counterpart detected with ANTARES
  30. Fermi GRB 211023A: Global MASTER-Net observations report
  31. GRB 211023A: AGILE detection
  32. GRB 211022A: AstroSat CZTI detection
  33. GRB 211023B: Swift-XRT refined Analysis
  34. GRB 211023B: Enhanced Swift-XRT position
  35. GRB 211023A: Fermi GBM detection
  36. Swift GRB 211023B: Global MASTER-Net observations report
  37. Fermi GRB 211024A: Global MASTER-Net observations report
  38. GRB 211024A: Fermi GBM Final Real-time Localization
  39. GRB 211023A: Fermi-LAT detection
  40. GRB 211023B: Swift detection of a possibly short burst with an optical counterpart
  41. IceCube Alert 211023.36: Global MASTER-Net observations report
  42. GRB 211023A: Fermi GBM Final Real-time Localization
  43. IceCube-211023A - IceCube observation of a high-energy neutrino candidate track-like event
  44. IPN Triangulation of GRB 210927B
  45. GRB 211022A: GECAM detection
  46. AMON IC_HAWC NuEm-211020A: No neutrino counterpart detected with ANTARES
  47. GRB 211018A: Swift ToO observations
  48. GRB 211021A: BALROG localization (Fermi Trigger 656506979 / GRB 211021460)
  49. Fermi trigger No 656506979: Global MASTER-Net observations report
  50. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-211020A
  51. BepiColombo MGNS joins the IPN
  52. Fermi trigger No 656268212: Global MASTER-Net observations report
  53. GRB 211018A: Fermi GBM observation
  54. GRB 211019A: Detection by GRBAlpha
  55. GRB 211018A: Detection by GRBAlpha
  56. Fermi GRB 211019A: Global MASTER-Net observations report
  57. GRB 211018A: Fermi-LAT detection
  58. GRB 211019A: BALROG localization (Fermi Trigger 656315976 / GRB 211019250)
  59. GRB 211019A: Fermi GBM Final Real-time Localization
  60. Fermi trigger No 656288898: Global MASTER-Net observations report
  61. Swift GRB211017.99: Global MASTER-Net observations report
  62. Integral GRB211016.42: Global MASTER-Net observations report
  63. IceCube-210922A: Hard X-ray flux limit for JCMT/SCUBA2 source from NuSTAR observations
  64. Swift trigger 1078701: MITSuME Akeno optical upper limits
  65. Fermi trigger No 655673024: Global MASTER-Net observations report
  66. GRB 210919A: LDT optical observations and candidate host galaxies
  67. IceCube-20210922A: No optical counterparts found by MITSuME observations
  68. Swift Trigger 1078701: Mondy, CrAO, AbAO observations, possible optical counterpart
  69. Fermi trigger No 655646385: Global MASTER-Net observations report
  70. Swift GRB211010.45: Global MASTER-Net observations report
  71. Swift Trigger 1078701 is probably not a GRB
  72. Fermi Gamma-ray Burst Monitor trigger 211008665/655401471 is not a GRB
  73. IceCube-20210922A: DESNU Optical counterpart candidate from 5 nights of DECam observations
  74. GRB 211008A: BALROG localization (Fermi Trigger 655401471 / GRB 211008665)
  75. Fermi trigger No 655401471: Global MASTER-Net observations report
  76. GRB 210928A: MeerKAT detection
  77. IceCube-210922A: DESI Observations
  78. GECAM observation of a burst from SGR J1555.2-5402
  79. Konus-Wind detection of GRB 210928A
  80. Fermi trigger No 654854799: Global MASTER-Net observations report
  81. Correction to GCN 30915: GRB 210928A: Swift-XRT analysis
  82. GRB 210928A: Kinder SLT-40cm optical limits
  83. GRB 210930A: Swift-BAT refined analysis
  84. SGR 1935+2154: Swift/BAT-GUANO detection and arcminute localization
  85. GRB 210928A: Swift-XRT analysis (replaces GCN 30914)
  86. GRB 210928A: Swift-XRT refined Analysis
  87. GRB 210928A: Fermi GBM observation
  88. GRB 210928A: Fermi-LAT detection
  89. Swift GRB211001.03 / trigger 1076121 : MASTER OT retraction
  90. GRB 210927B: GECAM detection
  91. GRB 210930A: CAHA 2.2m telescope optical limit
  92. GRB 210927A: GIT optical follow-up of ZTF21acdwctm.
  93. Fermi trigger No 654739449: Global MASTER-Net observations report
  94. Swift GRB211001.03: Global MASTER-Net observations report
  95. Swift Trigger 1076121 is not a GRB
  96. Swift GRB211001.03: Global MASTER-Net OT detection
  97. GRB 210930A: Swift/UVOT Upper Limits
  98. GRB 210930A: Swift-XRT refined Analysis
  99. Swift GRB 210930A: Global MASTER-Net observations report
  100. GRB 210930A: Enhanced Swift-XRT position

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