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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 201216C: TSHAO, Terskol, Mondy optical upper limits
  2. Baksan Neutrino Observatory Alert 201230.40: Global MASTER-Net observations report
  3. GRB 201227A: Chilescope optical observations, possible optical counterpart
  4. GRB 201227A: GRAWITA VST-ESO PARANAL observations
  5. GRB 201227A: Fermi GBM observation
  6. GRB 201229A: AbAO optical afterglow detection, TSHAO optical upper limit
  7. GRB 201229A: SAO RAS optical observations
  8. GRB 201229A: Nanshan/NEXT optical upper limit
  9. GRB 201227A: Swift-XRT observations
  10. GRB 201223A: SVOM-GWAC detected the optical counterpart during prompt emission phase
  11. GRB 201229A: Swift-XRT refined Analysis
  12. GRB 201229A: Swift-BAT refined analysis
  13. GRB 201104B: Maidanak and CrAO optical observations
  14. Fermi GRB 201229B: Global MASTER-Net observations report
  15. Konus-Wind observation of GRB 201227A
  16. GRB 201229B: BALROG localization (Fermi Trigger 630948017 / GRB 201229639)
  17. GRB 201229B: Fermi GBM Final Real-time Localization
  18. GRB 201229A: Enhanced Swift-XRT position
  19. GRB 201229A: Swift detection of a burst with a possible optical counterpart
  20. GRB 201020B: Assy, Koshka, Mondy and Maidanak optical observations
  21. Baksan Neutrino Observatory Alert 201228.36: Global MASTER-Net observations report
  22. Fermi GRB 201228B: Global MASTER-Net observations report
  23. GRB 201228B: Fermi GBM Final Real-time Localization
  24. GRB 201227A: Insight-HXMT/HE detection
  25. GRB 201226A: Insight-HXMT/HE detection
  26. GRB 201227A: Tiled Swift observations
  27. GRB 201227A: Swift ToO observations
  28. GRB 201228A: Fermi GBM Final Real-time Localization
  29. IPN triangulation of GRB 201227A (short)
  30. ZTF20acozryr/AT2020yxz (GRB 201103B): Maidanak optical observations
  31. GRB 201223A: AROMA-N Optical Observation
  32. GRB 201227A: AGILE detection of a burst
  33. Fermi trigger No 630681391: Global MASTER-Net observations report
  34. GRB 201223A: Swift/UVOT Detection
  35. GRB 201223A: HCT optical upper limit
  36. Baksan Neutrino Observatory Alert 201225.54: Global MASTER-Net observations report
  37. GRB 201223A: AbAO optical observations
  38. GRB 201223A: 1.3m DFOT and 1.04m ST optical observations
  39. IceCube-201222A: No Candidate Counterparts from the Zwicky Transient Facility
  40. GRB 201223A: Swift-XRT refined Analysis
  41. GRB 201223A: Enhanced Swift-XRT position
  42. GRB 201223A: NOT optical upper limit and NEXT powerlaw decay
  43. GRB 201223A: GROWTH-India Telescope (GIT) photometric follow-up.
  44. GRB 201223A: Mondy and Kitab optical observations
  45. GRB 201223A: GWAC-F60A optical afterglow observations
  46. GRB 201223A: iTelescope optical afterglow observations
  47. GRB 201223A: MITSuME Akeno optical observation
  48. GRB 201223A: Swift-BAT refined analysis
  49. Baksan Neutrino Observatory Alert 201223.60: Global MASTER-Net observations report
  50. GRB 201223A: Fermi GBM Detection
  51. GRB 201223A: BOOTES-4/MET early optical observation
  52. GRB 201223A: Nanshan/NEXT early optical afterglow detection
  53. GRB 201223A: Swift detection of a burst with a bright optical counterpart
  54. Swift GRB201223.75: Global MASTER-Net OT detection
  55. Swift GRB201223.75: Global MASTER-Net observations report
  56. Swift-XRT observations of Icecube 201222A
  57. IceCube-201222A: Upper limits from a search for additional neutrino events in IceCube
  58. IceCube-201221A: Upper limits from a search for additional neutrino events in IceCube
  59. IceCube-201222A: No significant detection in HAWC
  60. IceCube-201221A: No significant detection in HAWC
  61. GRB 201221A: Konus-Wind detection and joint Konus-Wind + Swift-BAT spectral analysis
  62. GRB 201221A: REM early-time afterglow detection
  63. GRB 201221D: 3.6m DOT optical observations
  64. GRB 201221B: Insight-HXMT/HE detection
  65. IceCube-201221A: Upper limits from Insight-HXMT/HE observations
  66. Fermi trigger No 630389391: Global MASTER-Net observations report
  67. GRB 201221D: SMA submm observation
  68. Fermi GRB 201222B: Global MASTER-Net observations report
  69. GRB 201221D: MMT MMIRS detection of marginally extended source
  70. GRB 201221D: LCOGT upper limits
  71. GRB 201221D: Fermi GBM detection
  72. GRB 201221D: Swift-BAT refined analysis
  73. Swift Trigger 1014012 (possible GRB 201221C) is likely not an astrophysical event
  74. GRB 201216A - further Swift-XRT observations
  75. Fermi-LAT Gamma-ray Observations of IceCube-201222A
  76. Fermi-LAT Gamma-ray Observations of IceCube-201221A
  77. IceCube-201222A: not observable by Fermi-GBM
  78. GRB 201221D: Archival PS1 Imaging of the Putative Host Galaxy
  79. Short GRB201221D: High Redshift from OSIRIS/GTC
  80. IceCube-201222A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  81. Konus-Wind detection of GRB 201221D (short)
  82. GRB 201221D: Swift/UVOT Upper Limits
  83. GRB 201221D: Lowell Discovery Telescope afterglow observations
  84. GRB 201222B: BALROG localization (Fermi Trigger / GRB 201222461)
  85. GRB 201222B: Fermi GBM Final Real-time Localization
  86. GRB 201221D: FRAM-ORM optical limit
  87. GRB 201221D: Swift-XRT refined Analysis
  88. IceCube Alert 201222.04: Global MASTER-Net observations report
  89. Swift GRB 201221D: Global MASTER-Net observations report
  90. Fermi GRB 201221E: Global MASTER-Net observations report
  91. IceCube-201222A: IceCube observation of a high-energy neutrino candidate event
  92. GRB 201221D: Enhanced Swift-XRT position
  93. GRB 201221D: Nanshan/NEXT early optical upper limit
  94. GRB 201221D: candidate optical counterpart from the NOT
  95. GRB 201221A: Swift-BAT refined analysis
  96. GRB 201222A: Fermi GBM Final Real-time Localization
  97. GRB 201221E: Fermi GBM Final Real-time Localization
  98. GRB 201221D: Prompt enhanced Swift-XRT position
  99. GRB 201221D: Swift detection of a bright short burst
  100. correction to GCN 29110 - Fermi GBM Sub-Threshold Detection of GRB 201221A

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