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

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