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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-210629A: Upper limits from Fermi-GBM Observations
  2. GRB 210627B: GECAM detection
  3. IceCube Alert 210629.76: Global MASTER-Net observations report
  4. GRB 210619B: Sayan observatory 1.6-m telescope observations
  5. IceCube-210629A - IceCube observation of a high-energy neutrino candidate track-like event
  6. GRB 210626A: Swift/XRT afterglow confirmation
  7. GRB 210626A: Fermi GBM observation
  8. GRB 210626A: CAHA 2.2m telescope optical limit
  9. GRB 210619B: Deep CAHA 2.2m detection and late-time light curve behavior
  10. GRB 210626A: Ondrejov D50 optical limit
  11. GRB 210626A: GIT optical upper limit
  12. Fermi trigger No 646443989: Global MASTER-Net observations report
  13. Fermi GRB 210627B: Global MASTER-Net observations report
  14. GRB 210627B: BALROG localization (Fermi Trigger 646509445/ GRB 210627748)
  15. GRB 210627B: Fermi GBM Final Real-time Localization
  16. Fermi GRB 210627A: Global MASTER-Net observations report
  17. GRB 210627A: Fermi GBM Final Real-time Localization
  18. GRB 210626A: Swift-XRT afterglow detection
  19. Fermi trigger No 646322348: Global MASTER-Net observations report
  20. Fermi GRB 210626A: Global MASTER-Net observations report
  21. GRB 210626A: Swift ToO observations
  22. GRB 210626A: Swift/BAT-GUANO detection and arcminute localization
  23. GRB 150428A: late-time radio observations
  24. GRB 210626A: Fermi GBM Final Real-time Localization
  25. GRB 210618A: 1.5m OSN optical upper limit
  26. Fermi GRB 210625A: Global MASTER-Net observations report
  27. GRB210619B: optical afterglow detection from Konkoly Observatory
  28. GRB 210625A: Fermi GBM Final Real-time Localization
  29. IPN triangulation of GRB 210624A (short)
  30. GRB 210622A: Swift-XRT observations
  31. GRB 210610B: T-CAT optical observations
  32. GRB 210619B: ASIM observation
  33. Fermi trigger No 646189108: Global MASTER-Net observations report
  34. Fermi GBM observation of a bright burst in the direction of SGR 1935+2154
  35. GRB 210618A: Swift-XRT afterglow detection
  36. Fermi trigger No 646194855: Global MASTER-Net observations report
  37. GRB 210622A: Swift ToO observations
  38. GRB 210619B: Even further SAO RAS optical observations
  39. GRB 210619B: Mini-MegaTORTORA early optical observations
  40. Fermi GRB 210622B: Global MASTER-Net observations report
  41. GRB 210622A: Fermi GBM detection
  42. GRB 210619B: Abbey Ridge Observatory optical afterglow observation
  43. GRB 210619B: SPI-ACS/INTEGRAL observations
  44. GRB 210619B: Further SAO RAS optical observations
  45. GRB 210622A: Swift/BAT-GUANO detection and arcminute localization of a long burst
  46. GRB 210619B: possibility of lensed visible afterglow?
  47. GECAM detection of GRB 210622B
  48. GRB 210619B: AbAO optical observations
  49. GRB 210622B: Fermi GBM Final Real-time Localization
  50. GRB 210622A: Fermi GBM Final Real-time Localization
  51. Swift Trigger 1057131: detection of a burst from SGR Swift J1555.2-5402
  52. Swift GRB210621.71: Global MASTER-Net observations report
  53. GRB 210619B: NOT optical observations
  54. GRB 210619B: 1.5m OSN optical observation
  55. GRB 210619B: iTelescope optical afterglow observation
  56. GRB 210619B: SAO RAS optical observations
  57. GRB 210619B: SEDM Optical Observations
  58. GRB 210619B: TNG NIR observations of the afterglow
  59. GRB 210619B: REM optical/NIR afterglow detection
  60. Fermi GRB 210621A: Global MASTER-Net observations report
  61. GRB 210619B: GIT optical follow-up and confirmation of jet-break
  62. GRB 210621A: Fermi GBM Final Real-time Localization
  63. GRB 210619B: CALET Gamma-Ray Burst Monitor detection
  64. GRB 210619B: SRG/ART-XC detection
  65. GRB 210619B: Swift-BAT refined analysis
  66. GRB 210619B: steepening of the decay observed at the D50
  67. GRB 210619B: Liverpool Telescope First Hour Observations
  68. GRB 210619B: Fermi GBM detection
  69. GRB 210619B: Swift/UVOT Detection
  70. GRB 210619B: Xinglong TNT optical observations
  71. Konus-Wind detection of GRB 210619B
  72. GRB 210619B: CAHA 2.2m photometric monitoring
  73. GRB 210619B: Liverpool Telescope r'-band observations
  74. GRB 210619B: KAIT Optical Detection
  75. GRB 210619B: Redshift from OSIRIS/GTC
  76. GRB 210619B: Liverpool telescope imaging of a red afterglow
  77. GRB 210619B: Fermi-LAT detection
  78. GRB 210619B: Swift-XRT refined Analysis
  79. GRB 210619B: SARA-KP 0.9m Optical Afterglow Detection
  80. GRB 210619B: Enhanced Swift-XRT position
  81. Fermi trigger No 645857659: Global MASTER-Net observations report
  82. GRB 210619B: iTelescope T18 detection
  83. GECAM detection of GRB 210619B
  84. GRB 210619B: Ondrejov D50 detection
  85. Swift GRB210619.99: Global MASTER-Net OT detection
  86. GRB 210619B: Swift detection of a bright burst and optical counterpart
  87. Swift GRB210619.99: Global MASTER-Net observations report
  88. Swift GRB210619.99: Global MASTER-Net OT detection
  89. GRB 210619A: BALROG localization (Fermi Trigger 645799548 / GRB 210619532)
  90. GRB 210619A: Fermi GBM Final Real-time Localization
  91. GRB 210618A: Swift/UVOT Upper Limits
  92. GRB 210618A: BOOTES-2/TELMA optical upper limit
  93. GRB 210618A: Swift-BAT refined analysis
  94. GRB 210618A: Fermi GBM observation
  95. GRB 210618A: Swift-XRT observations
  96. GRB 210618A: DDOTI upper limit for the optical afterglow
  97. GRB 210618A: Swift detection of a burst
  98. Swift GRB210618.07: Global MASTER-Net observations report
  99. GRB 210618A: Fermi GBM Final Real-time Localization
  100. GRB 210610B: Swift/UVOT Detection

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