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

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