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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 211106A: Swift/UVOT upper limits
  2. IPN triangulation of GRB 211106A (short)
  3. GRB 211112A: Fermi GBM Final Real-time Localization
  4. GRB 211110A: AstroSat CZTI detection
  5. Short GRB 211106A: spectroscopy of galaxies in the field
  6. GRB 211110A: GECAM detection
  7. Fermi trigger No 658214822: Global MASTER-Net observations report
  8. GRB 211107B: Swift-XRT afterglow detection
  9. GRB 211107A: GECAM detection
  10. GRB 211106A: VLT/FORS2 optical observations
  11. GRB 211106A, GROND observations
  12. GRB 211106A: Swift-XRT afterglow detection
  13. Fermi GRB 211109B: Global MASTER-Net observations report
  14. GRB 211023A: SAO RAS optical observations
  15. GRB 211107B: Swift-XRT observations
  16. MeerLICHT follow-up of GRB 211106A
  17. GRB 211109C: GECAM detection
  18. GRB 211107B: Swift ToO observations
  19. GRB 211109B: Fermi GBM Final Real-time Localization
  20. Fermi GRB 211109A: Global MASTER-Net observations report
  21. GRB 211109A: Fermi GBM Final Real-time Localization
  22. GRB 211107B: Swift/BAT detection
  23. GRB 211023A: A BdHN of type I
  24. Fermi GBM Sub-Threshold Detection of GRB 211106A
  25. Konus-Wind detection of GRB 211106A
  26. GRB 211023A: BTA spectroscopic redshift
  27. GRB 211107A: Fermi GBM Final Real-time Localization
  28. GRB 211106A: Swift-XRT observations
  29. GRB 211106A: Swift ToO observations
  30. GRB 211106A: Swift/BAT-GUANO candidate arcminute localization of a short burst
  31. GRB 211105A: MASTER optical inspection
  32. GRB 211105A: Swift/BAT-GUANO detection outside the coded FOV
  33. GRB 211105A: GECAM detection
  34. Swift Trigger 1082569 is probably not a GRB
  35. GRB 211105A: AGILE detection of a burst
  36. Fermi GBM trigger 657780594/211105201 is not a GRB
  37. GRB 211023A: optical detection by SBT in Ondrejov
  38. GRB 211023A: continued 1.3m DFOT Optical Observations and possible jet break
  39. Fermi trigger No 657742914: Global MASTER-Net observations report
  40. GRB 211104A: Fermi GBM Final Real-time Localization
  41. GRB 211023B: Subaru optical observation
  42. GRB 211024A: MITSuME Akeno optical observation
  43. GCN Viewer Now Available
  44. GRB 211102B: GECAM detection
  45. Fermi GRB 211102A: Global MASTER-Net observations report
  46. GRB 211102B: BALROG localization (Fermi Trigger 657554740 / GRB 211102587)
  47. GRB 211102B: Fermi GBM Final Real-time Localization
  48. GRB 211023B: MITSuME Akeno optical upper limits
  49. GRB 211102A: BALROG localization (Fermi Trigger 657533168 / GRB 211102338)
  50. GRB 211102A: Fermi GBM Final Real-time Localization
  51. GRB 211024B: Optical afterglow observation by Ondrejov D50
  52. GRB 211024A: 1.3m DFOT observations
  53. Fermi GRB 211031A: Global MASTER-Net observations report
  54. GRB 211031A: Fermi GBM Final Real-time Localization
  55. IPN triangulation of GRB 211022A
  56. GRB 211023A: 1.3m DFOT Optical Observations
  57. Konus-Wind detection of GRB 211023A
  58. GRB 2121023B: 6 GHz VLA radio upper limit
  59. GRB 211023A: Terskol optical observations
  60. AMON NuEm-211020A: No Candidate Counterparts from Swift-XRT follow up observations
  61. GRB 211023A: continued Mondy optical observations
  62. GRB 211024A: Swift-XRT source 4 is not an afterglow.
  63. GRB 211023B: NUTTelA-TAO / BSTI Early Optical Limits (Preliminary)
  64. Fermi GRB 211027A: Global MASTER-Net observations report
  65. GRB 211024A: Possible afterglow candidate from GIT
  66. GRB 211024A: Swift-XRT observations
  67. GRB 211027A: Fermi GBM Final Real-time Localization
  68. GRB 211024A: Fermi GBM detection
  69. GRB 211018A: Swift-XRT observations
  70. GRB 211025A: Optical Afterglow Detection
  71. GRB211023A: optical afterglow detection from Konkoly Observatory
  72. GRB 211024A: Swift ToO observations
  73. GRB 211024A: Swift/BAT-GUANO detection and candidate arcminute localization of a short burst
  74. GRB 211024B: Swift/UVOT detection
  75. GRB 211023A: Mondy optical observations
  76. GRB 211023B: Mondy optical afterglow confirmation
  77. GRB 211023B: Gemini-North Optical Observations
  78. Swift GRB 211025A: Global MASTER-Net observations report
  79. GRB 211023B: LDT Optical Afterglow Detection
  80. IceCube-211023A: Upper limits from a search for additional neutrino events in IceCube
  81. Correction to GCN 30965: GRB 211023A: Fermi GBM detection
  82. GRB 211025A: Swift-BAT refined analysis
  83. GRB 211025A: Swift-XRT refined Analysis
  84. GRB 211024B: CAHA 2.2m Detection; ultra-long GRB?
  85. GRB 211024B: Swift-XRT refined Analysis
  86. IPN Triangulation of GRB 211019A
  87. Possible Short GRB 211023B: CAHA 2.2m Detection
  88. GRB 211025A: Swift/UVOT Detection
  89. GRB 211023A: 1.5m OSN optical observation
  90. GRB 211024B: Swift-BAT refined analysis
  91. GRB 210610B: Sintesz-Newton/CrAO optical observations
  92. GRB 211025A: Enhanced Swift-XRT position
  93. GRB 211025A: Swift detection of a burst
  94. GECAM detection of a short burst probably from SGR J1555.2-5402
  95. GRB 211024B: Nanshan/NEXT optical afterglow detection
  96. GRB 210919A: FORS2/VLT observations
  97. GRB 211023A: OAJ Bright Afterglow Confirmation
  98. Swift GRB 211024B: Global MASTER-Net observations report
  99. GRB 211024B: Swift detection of a burst
  100. GRB 211023B: Swift-BAT refined analysis

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