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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 211023A: MASTER OT J045237.07+851925.2 - optical counterpart discovery
  2. GRB 211023B: BOOTES-4/MET and 1.5m OSN optical upper limit
  3. GRB 211023B: Swift/UVOT Detection
  4. GRB 211024A: GECAM detection
  5. GRB 211023B: RATIR Optical and NIR Upper Limits
  6. GRB 211023B: TSHAO optical observation
  7. IceCube-211023A: No neutrino counterpart detected with ANTARES
  8. Fermi GRB 211023A: Global MASTER-Net observations report
  9. GRB 211023A: AGILE detection
  10. GRB 211022A: AstroSat CZTI detection
  11. GRB 211023B: Swift-XRT refined Analysis
  12. GRB 211023B: Enhanced Swift-XRT position
  13. GRB 211023A: Fermi GBM detection
  14. Swift GRB 211023B: Global MASTER-Net observations report
  15. Fermi GRB 211024A: Global MASTER-Net observations report
  16. GRB 211024A: Fermi GBM Final Real-time Localization
  17. GRB 211023A: Fermi-LAT detection
  18. GRB 211023B: Swift detection of a possibly short burst with an optical counterpart
  19. IceCube Alert 211023.36: Global MASTER-Net observations report
  20. GRB 211023A: Fermi GBM Final Real-time Localization
  21. IceCube-211023A - IceCube observation of a high-energy neutrino candidate track-like event
  22. IPN Triangulation of GRB 210927B
  23. GRB 211022A: GECAM detection
  24. AMON IC_HAWC NuEm-211020A: No neutrino counterpart detected with ANTARES
  25. GRB 211018A: Swift ToO observations
  26. GRB 211021A: BALROG localization (Fermi Trigger 656506979 / GRB 211021460)
  27. Fermi trigger No 656506979: Global MASTER-Net observations report
  28. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-211020A
  29. BepiColombo MGNS joins the IPN
  30. Fermi trigger No 656268212: Global MASTER-Net observations report
  31. GRB 211018A: Fermi GBM observation
  32. GRB 211019A: Detection by GRBAlpha
  33. GRB 211018A: Detection by GRBAlpha
  34. Fermi GRB 211019A: Global MASTER-Net observations report
  35. GRB 211018A: Fermi-LAT detection
  36. GRB 211019A: BALROG localization (Fermi Trigger 656315976 / GRB 211019250)
  37. GRB 211019A: Fermi GBM Final Real-time Localization
  38. Fermi trigger No 656288898: Global MASTER-Net observations report
  39. Swift GRB211017.99: Global MASTER-Net observations report
  40. Integral GRB211016.42: Global MASTER-Net observations report
  41. IceCube-210922A: Hard X-ray flux limit for JCMT/SCUBA2 source from NuSTAR observations
  42. Swift trigger 1078701: MITSuME Akeno optical upper limits
  43. Fermi trigger No 655673024: Global MASTER-Net observations report
  44. GRB 210919A: LDT optical observations and candidate host galaxies
  45. IceCube-20210922A: No optical counterparts found by MITSuME observations
  46. Swift Trigger 1078701: Mondy, CrAO, AbAO observations, possible optical counterpart
  47. Fermi trigger No 655646385: Global MASTER-Net observations report
  48. Swift GRB211010.45: Global MASTER-Net observations report
  49. Swift Trigger 1078701 is probably not a GRB
  50. Fermi Gamma-ray Burst Monitor trigger 211008665/655401471 is not a GRB
  51. IceCube-20210922A: DESNU Optical counterpart candidate from 5 nights of DECam observations
  52. GRB 211008A: BALROG localization (Fermi Trigger 655401471 / GRB 211008665)
  53. Fermi trigger No 655401471: Global MASTER-Net observations report
  54. GRB 210928A: MeerKAT detection
  55. IceCube-210922A: DESI Observations
  56. GECAM observation of a burst from SGR J1555.2-5402
  57. Konus-Wind detection of GRB 210928A
  58. Fermi trigger No 654854799: Global MASTER-Net observations report
  59. Correction to GCN 30915: GRB 210928A: Swift-XRT analysis
  60. GRB 210928A: Kinder SLT-40cm optical limits
  61. GRB 210930A: Swift-BAT refined analysis
  62. SGR 1935+2154: Swift/BAT-GUANO detection and arcminute localization
  63. GRB 210928A: Swift-XRT analysis (replaces GCN 30914)
  64. GRB 210928A: Swift-XRT refined Analysis
  65. GRB 210928A: Fermi GBM observation
  66. GRB 210928A: Fermi-LAT detection
  67. Swift GRB211001.03 / trigger 1076121 : MASTER OT retraction
  68. GRB 210927B: GECAM detection
  69. GRB 210930A: CAHA 2.2m telescope optical limit
  70. GRB 210927A: GIT optical follow-up of ZTF21acdwctm.
  71. Fermi trigger No 654739449: Global MASTER-Net observations report
  72. Swift GRB211001.03: Global MASTER-Net observations report
  73. Swift Trigger 1076121 is not a GRB
  74. Swift GRB211001.03: Global MASTER-Net OT detection
  75. GRB 210930A: Swift/UVOT Upper Limits
  76. GRB 210930A: Swift-XRT refined Analysis
  77. Swift GRB 210930A: Global MASTER-Net observations report
  78. GRB 210930A: Enhanced Swift-XRT position
  79. Fermi trigger No 654658271: Global MASTER-Net observations report
  80. Fermi GRB 210929B: Global MASTER-Net observations report
  81. GRB 210930A: Swift detection of a burst
  82. GRB 210929B: Fermi GBM Final Real-time Localization
  83. Fermi-LAT Gamma-ray Observations of IceCubeCascade-210926A
  84. GRB 210929A: Fermi GBM Final Real-time Localization
  85. GRB 210927A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 654396242)
  86. GRB 210925B: AstroSat CZTI detection
  87. IceCube-210922A: SMA observation for the JCMT candidate
  88. IPN triangulation of GRB 210925B
  89. GRB 210926A: AstroSat CZTI detection
  90. GRB 210919A: iTelescope T-11 upper limits
  91. IceCube-210926A: No neutrino counterpart candidates in ANTARES search
  92. GRB 210926A: GECAM detection
  93. GRB 210927A: Fermi GBM Final Real-time Localization
  94. GRB 210919A OSN 1.5m Source Confirmation
  95. GRB 210919A CAHA 2.2m Observations: Afterglow/Host Galaxy Candidate
  96. IceCube-210922A: JCMT/SCUBA2 observations
  97. GRB 210925A: GECAM detection
  98. GRB 210925A: Fermi GBM Final Real-time Localization
  99. GRB 210919A: Chandra rapid ToO upper limit
  100. GRB 210924A: Fermi GBM Final Real-time Localization

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