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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 201227A: Insight-HXMT/HE detection
  2. GRB 201226A: Insight-HXMT/HE detection
  3. GRB 201227A: Tiled Swift observations
  4. GRB 201227A: Swift ToO observations
  5. GRB 201228A: Fermi GBM Final Real-time Localization
  6. IPN triangulation of GRB 201227A (short)
  7. ZTF20acozryr/AT2020yxz (GRB 201103B): Maidanak optical observations
  8. GRB 201223A: AROMA-N Optical Observation
  9. GRB 201227A: AGILE detection of a burst
  10. Fermi trigger No 630681391: Global MASTER-Net observations report
  11. GRB 201223A: Swift/UVOT Detection
  12. GRB 201223A: HCT optical upper limit
  13. Baksan Neutrino Observatory Alert 201225.54: Global MASTER-Net observations report
  14. GRB 201223A: AbAO optical observations
  15. GRB 201223A: 1.3m DFOT and 1.04m ST optical observations
  16. IceCube-201222A: No Candidate Counterparts from the Zwicky Transient Facility
  17. GRB 201223A: Swift-XRT refined Analysis
  18. GRB 201223A: Enhanced Swift-XRT position
  19. GRB 201223A: NOT optical upper limit and NEXT powerlaw decay
  20. GRB 201223A: GROWTH-India Telescope (GIT) photometric follow-up.
  21. GRB 201223A: Mondy and Kitab optical observations
  22. GRB 201223A: GWAC-F60A optical afterglow observations
  23. GRB 201223A: iTelescope optical afterglow observations
  24. GRB 201223A: MITSuME Akeno optical observation
  25. GRB 201223A: Swift-BAT refined analysis
  26. Baksan Neutrino Observatory Alert 201223.60: Global MASTER-Net observations report
  27. GRB 201223A: Fermi GBM Detection
  28. GRB 201223A: BOOTES-4/MET early optical observation
  29. GRB 201223A: Nanshan/NEXT early optical afterglow detection
  30. GRB 201223A: Swift detection of a burst with a bright optical counterpart
  31. Swift GRB201223.75: Global MASTER-Net OT detection
  32. Swift GRB201223.75: Global MASTER-Net observations report
  33. Swift-XRT observations of Icecube 201222A
  34. IceCube-201222A: Upper limits from a search for additional neutrino events in IceCube
  35. IceCube-201221A: Upper limits from a search for additional neutrino events in IceCube
  36. IceCube-201222A: No significant detection in HAWC
  37. IceCube-201221A: No significant detection in HAWC
  38. GRB 201221A: Konus-Wind detection and joint Konus-Wind + Swift-BAT spectral analysis
  39. GRB 201221A: REM early-time afterglow detection
  40. GRB 201221D: 3.6m DOT optical observations
  41. GRB 201221B: Insight-HXMT/HE detection
  42. IceCube-201221A: Upper limits from Insight-HXMT/HE observations
  43. Fermi trigger No 630389391: Global MASTER-Net observations report
  44. GRB 201221D: SMA submm observation
  45. Fermi GRB 201222B: Global MASTER-Net observations report
  46. GRB 201221D: MMT MMIRS detection of marginally extended source
  47. GRB 201221D: LCOGT upper limits
  48. GRB 201221D: Fermi GBM detection
  49. GRB 201221D: Swift-BAT refined analysis
  50. Swift Trigger 1014012 (possible GRB 201221C) is likely not an astrophysical event
  51. GRB 201216A - further Swift-XRT observations
  52. Fermi-LAT Gamma-ray Observations of IceCube-201222A
  53. Fermi-LAT Gamma-ray Observations of IceCube-201221A
  54. IceCube-201222A: not observable by Fermi-GBM
  55. GRB 201221D: Archival PS1 Imaging of the Putative Host Galaxy
  56. Short GRB201221D: High Redshift from OSIRIS/GTC
  57. IceCube-201222A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  58. Konus-Wind detection of GRB 201221D (short)
  59. GRB 201221D: Swift/UVOT Upper Limits
  60. GRB 201221D: Lowell Discovery Telescope afterglow observations
  61. GRB 201222B: BALROG localization (Fermi Trigger / GRB 201222461)
  62. GRB 201222B: Fermi GBM Final Real-time Localization
  63. GRB 201221D: FRAM-ORM optical limit
  64. GRB 201221D: Swift-XRT refined Analysis
  65. IceCube Alert 201222.04: Global MASTER-Net observations report
  66. Swift GRB 201221D: Global MASTER-Net observations report
  67. Fermi GRB 201221E: Global MASTER-Net observations report
  68. IceCube-201222A: IceCube observation of a high-energy neutrino candidate event
  69. GRB 201221D: Enhanced Swift-XRT position
  70. GRB 201221D: Nanshan/NEXT early optical upper limit
  71. GRB 201221D: candidate optical counterpart from the NOT
  72. GRB 201221A: Swift-BAT refined analysis
  73. GRB 201222A: Fermi GBM Final Real-time Localization
  74. GRB 201221E: Fermi GBM Final Real-time Localization
  75. GRB 201221D: Prompt enhanced Swift-XRT position
  76. GRB 201221D: Swift detection of a bright short burst
  77. correction to GCN 29110 - Fermi GBM Sub-Threshold Detection of GRB 201221A
  78. Fermi GBM Sub-Threshold Detection of GRB 201221A
  79. GRB 201221A: Swift/UVOT Upper Limits
  80. GRB 201221A: Swift-XRT refined Analysis
  81. GRB 201221C: MASTER optical observtion
  82. Swift Trigger 1014012: possible GRB 201221C
  83. GRB 201221A: Enhanced Swift-XRT position
  84. IceCube-201221A: not observable by Fermi-GBM
  85. IceCube-201221A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  86. IceCube-201221A: IceCube observation of a high-energy neutrino candidate event
  87. GRB 201221B: Fermi GBM Final Real-time Localization
  88. GRB 201221A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 5.7
  89. GRB 201221A: FRAM-Auger optical limit
  90. Swift GRB 201221A: Global MASTER-Net observations report
  91. GRB 201221A: Prompt enhanced Swift-XRT position
  92. GRB 201221A: Swift detection of a burst
  93. Konus-Wind observation of GRB 201218A
  94. GRB 201209A: Mondy optical observations, afterglow confirmation
  95. GRB 201214A: TSHAO optical upper limit
  96. GRB 201214A: Swift-XRT afterglow detection
  97. GRB 201214A: 1.3m DFOT, optical upper limits
  98. IPN triangulation of GRB 201218A
  99. Fermi GRB 201218B: Global MASTER-Net observations report
  100. GRB 201218B: Fermi GBM Final Real-time Localization

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