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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 201228A: Fermi GBM Final Real-time Localization
  2. IPN triangulation of GRB 201227A (short)
  3. ZTF20acozryr/AT2020yxz (GRB 201103B): Maidanak optical observations
  4. GRB 201223A: AROMA-N Optical Observation
  5. GRB 201227A: AGILE detection of a burst
  6. Fermi trigger No 630681391: Global MASTER-Net observations report
  7. GRB 201223A: Swift/UVOT Detection
  8. GRB 201223A: HCT optical upper limit
  9. Baksan Neutrino Observatory Alert 201225.54: Global MASTER-Net observations report
  10. GRB 201223A: AbAO optical observations
  11. GRB 201223A: 1.3m DFOT and 1.04m ST optical observations
  12. IceCube-201222A: No Candidate Counterparts from the Zwicky Transient Facility
  13. GRB 201223A: Swift-XRT refined Analysis
  14. GRB 201223A: Enhanced Swift-XRT position
  15. GRB 201223A: NOT optical upper limit and NEXT powerlaw decay
  16. GRB 201223A: GROWTH-India Telescope (GIT) photometric follow-up.
  17. GRB 201223A: Mondy and Kitab optical observations
  18. GRB 201223A: GWAC-F60A optical afterglow observations
  19. GRB 201223A: iTelescope optical afterglow observations
  20. GRB 201223A: MITSuME Akeno optical observation
  21. GRB 201223A: Swift-BAT refined analysis
  22. Baksan Neutrino Observatory Alert 201223.60: Global MASTER-Net observations report
  23. GRB 201223A: Fermi GBM Detection
  24. GRB 201223A: BOOTES-4/MET early optical observation
  25. GRB 201223A: Nanshan/NEXT early optical afterglow detection
  26. GRB 201223A: Swift detection of a burst with a bright optical counterpart
  27. Swift GRB201223.75: Global MASTER-Net OT detection
  28. Swift GRB201223.75: Global MASTER-Net observations report
  29. Swift-XRT observations of Icecube 201222A
  30. IceCube-201222A: Upper limits from a search for additional neutrino events in IceCube
  31. IceCube-201221A: Upper limits from a search for additional neutrino events in IceCube
  32. IceCube-201222A: No significant detection in HAWC
  33. IceCube-201221A: No significant detection in HAWC
  34. GRB 201221A: Konus-Wind detection and joint Konus-Wind + Swift-BAT spectral analysis
  35. GRB 201221A: REM early-time afterglow detection
  36. GRB 201221D: 3.6m DOT optical observations
  37. GRB 201221B: Insight-HXMT/HE detection
  38. IceCube-201221A: Upper limits from Insight-HXMT/HE observations
  39. Fermi trigger No 630389391: Global MASTER-Net observations report
  40. GRB 201221D: SMA submm observation
  41. Fermi GRB 201222B: Global MASTER-Net observations report
  42. GRB 201221D: MMT MMIRS detection of marginally extended source
  43. GRB 201221D: LCOGT upper limits
  44. GRB 201221D: Fermi GBM detection
  45. GRB 201221D: Swift-BAT refined analysis
  46. Swift Trigger 1014012 (possible GRB 201221C) is likely not an astrophysical event
  47. GRB 201216A - further Swift-XRT observations
  48. Fermi-LAT Gamma-ray Observations of IceCube-201222A
  49. Fermi-LAT Gamma-ray Observations of IceCube-201221A
  50. IceCube-201222A: not observable by Fermi-GBM
  51. GRB 201221D: Archival PS1 Imaging of the Putative Host Galaxy
  52. Short GRB201221D: High Redshift from OSIRIS/GTC
  53. IceCube-201222A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  54. Konus-Wind detection of GRB 201221D (short)
  55. GRB 201221D: Swift/UVOT Upper Limits
  56. GRB 201221D: Lowell Discovery Telescope afterglow observations
  57. GRB 201222B: BALROG localization (Fermi Trigger / GRB 201222461)
  58. GRB 201222B: Fermi GBM Final Real-time Localization
  59. GRB 201221D: FRAM-ORM optical limit
  60. GRB 201221D: Swift-XRT refined Analysis
  61. IceCube Alert 201222.04: Global MASTER-Net observations report
  62. Swift GRB 201221D: Global MASTER-Net observations report
  63. Fermi GRB 201221E: Global MASTER-Net observations report
  64. IceCube-201222A: IceCube observation of a high-energy neutrino candidate event
  65. GRB 201221D: Enhanced Swift-XRT position
  66. GRB 201221D: Nanshan/NEXT early optical upper limit
  67. GRB 201221D: candidate optical counterpart from the NOT
  68. GRB 201221A: Swift-BAT refined analysis
  69. GRB 201222A: Fermi GBM Final Real-time Localization
  70. GRB 201221E: Fermi GBM Final Real-time Localization
  71. GRB 201221D: Prompt enhanced Swift-XRT position
  72. GRB 201221D: Swift detection of a bright short burst
  73. correction to GCN 29110 - Fermi GBM Sub-Threshold Detection of GRB 201221A
  74. Fermi GBM Sub-Threshold Detection of GRB 201221A
  75. GRB 201221A: Swift/UVOT Upper Limits
  76. GRB 201221A: Swift-XRT refined Analysis
  77. GRB 201221C: MASTER optical observtion
  78. Swift Trigger 1014012: possible GRB 201221C
  79. GRB 201221A: Enhanced Swift-XRT position
  80. IceCube-201221A: not observable by Fermi-GBM
  81. IceCube-201221A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  82. IceCube-201221A: IceCube observation of a high-energy neutrino candidate event
  83. GRB 201221B: Fermi GBM Final Real-time Localization
  84. GRB 201221A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 5.7
  85. GRB 201221A: FRAM-Auger optical limit
  86. Swift GRB 201221A: Global MASTER-Net observations report
  87. GRB 201221A: Prompt enhanced Swift-XRT position
  88. GRB 201221A: Swift detection of a burst
  89. Konus-Wind observation of GRB 201218A
  90. GRB 201209A: Mondy optical observations, afterglow confirmation
  91. GRB 201214A: TSHAO optical upper limit
  92. GRB 201214A: Swift-XRT afterglow detection
  93. GRB 201214A: 1.3m DFOT, optical upper limits
  94. IPN triangulation of GRB 201218A
  95. Fermi GRB 201218B: Global MASTER-Net observations report
  96. GRB 201218B: Fermi GBM Final Real-time Localization
  97. Fermi GRB 201218A: Global MASTER-Net observations report
  98. GRB201216C: No significant detection in HAWC
  99. GRB 201216C: Liverpool Telescope First Hour Observations
  100. Konus-Wind detection of GRB 201216C

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