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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 210105A: Fermi GBM Final Real-time Localization
  2. GRB 210104A: Swift-XRT refined Analysis
  3. GRB 210104B: Swift/UVOT Upper Limits
  4. Konus-Wind detection of GRB 210104A
  5. GRB 210104A: 1.3m DFOT Optical Afterglow Detection
  6. GRB 210104B: Swift-XRT refined Analysis
  7. GRB 210104B: Assy optical upper limit
  8. GRB 210104A: DOAO optical afterglow observations
  9. GRB 210104B: Enhanced Swift-XRT position
  10. GRB 210104A: Nanshan/NEXT optical powerlaw decay
  11. GRB 210104A: Swift-BAT refined analysis
  12. GRB 210104B: Nanshan/NEXT optical upper limit
  13. GRB 210104B: BOOTES network optical upper limit
  14. GRB 210104A: MASTER OT rebrightening detection
  15. GRB 210104A: Swift/UVOT Detection
  16. GRB 210104A: Fermi GBM detection
  17. GRB 210104A: Enhanced Swift-XRT position
  18. GRB 210102B: Tiled Swift observations
  19. GRB 210104B: Swift detection of a burst
  20. Swift GRB210104.88: Global MASTER-Net observations report
  21. GRB 210104A: MITSuME Ishigaki optical observation
  22. GRB 210102B: Assy optical observations
  23. Fermi GRB 210104A: Global MASTER-Net observations report
  24. GRB 210104A: Assy optical observations
  25. GRB 210104A: MITSuME Akeno optical observation
  26. GRB 210104A: BOOTES-4/MET early optical afterglow detection
  27. GRB 210104A: GWAC-F60A optical afterglow observations
  28. GRB 210104A: BALROG localization (Fermi Trigger 631452424 / GRB 210104477)
  29. GRB 210104A: Swift detection of a burst with a bright optical counterpart
  30. GRB 210104A: Fermi GBM Final Real-time Localization
  31. GRB 210102C: Swift-BAT refined analysis
  32. GRB 210102B: Swift-XRT observations
  33. Fermi GRB 210102C: Global MASTER-Net observations report
  34. GRB 210102C: Fermi GBM detection
  35. Swift GRB 210102C: Global MASTER-Net observations report
  36. GRB 210102C: Swift detection of a burst
  37. MAXI GRB210102.38: Global MASTER-Net observations report
  38. GRB 210102B: Tiled Swift observations
  39. GRB 210102B: MAXI/GSC detection
  40. Fermi GRB 210101A: Global MASTER-Net observations report
  41. INTEGRAL Weak #8913: AROMA-N Optical Observation
  42. Swift Trigger 1015615 is not a GRB
  43. Swift GRB210102.01: Global MASTER-Net observations report
  44. Fermi trigger No 631226368: Global MASTER-Net observations report
  45. Fermi trigger No 631119348: Global MASTER-Net observations report
  46. GRB 210101A: BALROG localization (Fermi Trigger 631205591 / GRB 210101620)
  47. GRB 210101A: Fermi GBM Final Real-time Localization
  48. Fermi trigger No 631113166: Global MASTER-Net observations report
  49. GRB 201229A: Swift/UVOT Detection
  50. Fermi trigger No 631118376: Global MASTER-Net observations report
  51. Fermi trigger No 631104264: Global MASTER-Net observations report
  52. GRB 201216C: TSHAO, Terskol, Mondy optical upper limits
  53. Baksan Neutrino Observatory Alert 201230.40: Global MASTER-Net observations report
  54. GRB 201227A: Chilescope optical observations, possible optical counterpart
  55. GRB 201227A: GRAWITA VST-ESO PARANAL observations
  56. GRB 201227A: Fermi GBM observation
  57. GRB 201229A: AbAO optical afterglow detection, TSHAO optical upper limit
  58. GRB 201229A: SAO RAS optical observations
  59. GRB 201229A: Nanshan/NEXT optical upper limit
  60. GRB 201227A: Swift-XRT observations
  61. GRB 201223A: SVOM-GWAC detected the optical counterpart during prompt emission phase
  62. GRB 201229A: Swift-XRT refined Analysis
  63. GRB 201229A: Swift-BAT refined analysis
  64. GRB 201104B: Maidanak and CrAO optical observations
  65. Fermi GRB 201229B: Global MASTER-Net observations report
  66. Konus-Wind observation of GRB 201227A
  67. GRB 201229B: BALROG localization (Fermi Trigger 630948017 / GRB 201229639)
  68. GRB 201229B: Fermi GBM Final Real-time Localization
  69. GRB 201229A: Enhanced Swift-XRT position
  70. GRB 201229A: Swift detection of a burst with a possible optical counterpart
  71. GRB 201020B: Assy, Koshka, Mondy and Maidanak optical observations
  72. Baksan Neutrino Observatory Alert 201228.36: Global MASTER-Net observations report
  73. Fermi GRB 201228B: Global MASTER-Net observations report
  74. GRB 201228B: Fermi GBM Final Real-time Localization
  75. GRB 201227A: Insight-HXMT/HE detection
  76. GRB 201226A: Insight-HXMT/HE detection
  77. GRB 201227A: Tiled Swift observations
  78. GRB 201227A: Swift ToO observations
  79. GRB 201228A: Fermi GBM Final Real-time Localization
  80. IPN triangulation of GRB 201227A (short)
  81. ZTF20acozryr/AT2020yxz (GRB 201103B): Maidanak optical observations
  82. GRB 201223A: AROMA-N Optical Observation
  83. GRB 201227A: AGILE detection of a burst
  84. Fermi trigger No 630681391: Global MASTER-Net observations report
  85. GRB 201223A: Swift/UVOT Detection
  86. GRB 201223A: HCT optical upper limit
  87. Baksan Neutrino Observatory Alert 201225.54: Global MASTER-Net observations report
  88. GRB 201223A: AbAO optical observations
  89. GRB 201223A: 1.3m DFOT and 1.04m ST optical observations
  90. IceCube-201222A: No Candidate Counterparts from the Zwicky Transient Facility
  91. GRB 201223A: Swift-XRT refined Analysis
  92. GRB 201223A: Enhanced Swift-XRT position
  93. GRB 201223A: NOT optical upper limit and NEXT powerlaw decay
  94. GRB 201223A: GROWTH-India Telescope (GIT) photometric follow-up.
  95. GRB 201223A: Mondy and Kitab optical observations
  96. GRB 201223A: GWAC-F60A optical afterglow observations
  97. GRB 201223A: iTelescope optical afterglow observations
  98. GRB 201223A: MITSuME Akeno optical observation
  99. GRB 201223A: Swift-BAT refined analysis
  100. Baksan Neutrino Observatory Alert 201223.60: Global MASTER-Net observations report

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