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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 210619B: 1.5m OSN optical observation
  2. GRB 210619B: iTelescope optical afterglow observation
  3. GRB 210619B: SAO RAS optical observations
  4. GRB 210619B: SEDM Optical Observations
  5. GRB 210619B: TNG NIR observations of the afterglow
  6. GRB 210619B: REM optical/NIR afterglow detection
  7. Fermi GRB 210621A: Global MASTER-Net observations report
  8. GRB 210619B: GIT optical follow-up and confirmation of jet-break
  9. GRB 210621A: Fermi GBM Final Real-time Localization
  10. GRB 210619B: CALET Gamma-Ray Burst Monitor detection
  11. GRB 210619B: SRG/ART-XC detection
  12. GRB 210619B: Swift-BAT refined analysis
  13. GRB 210619B: steepening of the decay observed at the D50
  14. GRB 210619B: Liverpool Telescope First Hour Observations
  15. GRB 210619B: Fermi GBM detection
  16. GRB 210619B: Swift/UVOT Detection
  17. GRB 210619B: Xinglong TNT optical observations
  18. Konus-Wind detection of GRB 210619B
  19. GRB 210619B: CAHA 2.2m photometric monitoring
  20. GRB 210619B: Liverpool Telescope r'-band observations
  21. GRB 210619B: KAIT Optical Detection
  22. GRB 210619B: Redshift from OSIRIS/GTC
  23. GRB 210619B: Liverpool telescope imaging of a red afterglow
  24. GRB 210619B: Fermi-LAT detection
  25. GRB 210619B: Swift-XRT refined Analysis
  26. GRB 210619B: SARA-KP 0.9m Optical Afterglow Detection
  27. GRB 210619B: Enhanced Swift-XRT position
  28. Fermi trigger No 645857659: Global MASTER-Net observations report
  29. GRB 210619B: iTelescope T18 detection
  30. GECAM detection of GRB 210619B
  31. GRB 210619B: Ondrejov D50 detection
  32. Swift GRB210619.99: Global MASTER-Net OT detection
  33. GRB 210619B: Swift detection of a bright burst and optical counterpart
  34. Swift GRB210619.99: Global MASTER-Net observations report
  35. Swift GRB210619.99: Global MASTER-Net OT detection
  36. GRB 210619A: BALROG localization (Fermi Trigger 645799548 / GRB 210619532)
  37. GRB 210619A: Fermi GBM Final Real-time Localization
  38. GRB 210618A: Swift/UVOT Upper Limits
  39. GRB 210618A: BOOTES-2/TELMA optical upper limit
  40. GRB 210618A: Swift-BAT refined analysis
  41. GRB 210618A: Fermi GBM observation
  42. GRB 210618A: Swift-XRT observations
  43. GRB 210618A: DDOTI upper limit for the optical afterglow
  44. GRB 210618A: Swift detection of a burst
  45. Swift GRB210618.07: Global MASTER-Net observations report
  46. GRB 210618A: Fermi GBM Final Real-time Localization
  47. GRB 210610B: Swift/UVOT Detection
  48. GRB 210610A: Swift/UVOT Detection
  49. GRB 210610B: CrAO/ZTSH continued optical observations and light curve
  50. Fermi trigger No 645485036: Global MASTER-Net observations report
  51. GRB 210610B: AbAO optical observations
  52. GRB 201008A: Fermi GBM observation
  53. GRB 210323B: Fermi GBM observation
  54. Fermi GRB 210615A: Global MASTER-Net observations report
  55. GRB 210615A: Fermi GBM Final Real-time Localization
  56. GRB 210610B: REM optical/NIR observations of the afterglow
  57. Swift-BAT Trigger 1055000/GRB210612.54: MASTER optical source observation
  58. Follow-up on HAWC Transient Monitoring Alert J0020+3108
  59. Swift ToO Observations of HAWC transient J0020+3108
  60. GRB 210605B: Swift-XRT afterglow detection
  61. GRB 210610A: Fermi GBM observations
  62. GRB 210610A: CAHA 2.2m Second Epoch
  63. GRB 210610B: iTelescope optical afterglow observations
  64. GRB 210610B: Further SAO RAS optical observations
  65. GRB 210610A: SAO RAS optical observations
  66. GRB 210610B: optical observations from Burke-Gaffney Observatory and Abbey Ridge Observatory
  67. GRB 210610B: Continued KAIT Optical Detection
  68. GRB 210610B: optical photometry of afterglow at INASAN/Simeiz
  69. GRB 210421B: Fermi GBM detection
  70. Swift GRB210612.54: Global MASTER-Net observations report
  71. GRB 210607C: AstroSat CZTI detection
  72. Swift-BAT Trigger 1055000: Swift detection of an outburst from 4U 1543-47
  73. GRB210610B: SARA-KP 0.9m Optical Afterglow Detection
  74. GRB 210610B: MITSuME Akeno optical observation
  75. GRB 201228B: Fermi GBM observation
  76. GRB 210610B: VLA detection
  77. GRB 210610B: ALMA detection
  78. GRB 210610B: Liverpool Telescope optical photometry
  79. GRB 210610B: CrAO/ZTSH optical observations and light curve
  80. GRB 210610A: CrAO/ZTSH optical observations
  81. GRB 210610B: CrAO/ZTSH optical observations (correction to the GCN circ. 30212)
  82. GRB 210610A: CrAO/ZTSH optical observations
  83. GRB 210610A: CAHA 2.2m observations and light-curve behavior
  84. GRB 210606A: Fermi GBM detection
  85. GRB 210605B: Fermi GBM detection
  86. GRB 210610B: Swift-XRT refined Analysis
  87. GRB 210610B: Swift-BAT refined analysis
  88. GRB 210610B: Zwicky Transient Facility afterglow detection
  89. GRB 210610B: optical afterglow observations
  90. GRB 210610B: KAIT Optical Detection
  91. GRB 210610A: KAIT Optical Detection
  92. GRB 210607C: Insight-HXMT/HE detection
  93. GRB 210610B: Spectroscopy and redshift confirmation with the Himalayan Chandra Telescope
  94. GRB 210610A: Spectroscopy and redshift confirmation with the Himalayan Chandra Telescope
  95. GRB 210610B: Fermi GBM detection
  96. GRB 210610B: University of Siena Observatory optical photometry of the afterglow
  97. Konus-Wind detection of GRB 210610A
  98. Konus-Wind detection of GRB 210610B
  99. GRB 210610B: AGILE detection
  100. GRB 210610B: Redshift confirmation from GTC

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