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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"

8294 results found.

  1. GRB 210207B: Swift detection of a burst with a bright optical counterpart
  2. GRB 210204A: Swift ToO observations
  3. GRB 210205A: Swift detection of a burst
  4. GRB 210120A : 1.3m DFOT optical observations
  5. GRB 210120A(MASTER OT J105242.66+152355.0 / AT2021axc): Mondy optical observations
  6. GRB 210119A (Swift J1851.2-6148): Swift-BAT refined analysis
  7. GECAM detection of a short GRB 210119A or a new SGR candidate Swift J1851.2-6148
  8. GRB 210112A: 1.3m DFOT Optical upper limit
  9. GRB 210112A: OSN Reddened Afterglow Detection
  10. NuEm-210111A : No neutrino counterpart in ANTARES
  11. GRB 210112A: Kitab a optical upper limit
  12. GRB 210112A: Swift detection of a burst with an optical counterpart
  13. GRB 210102B: Assy optical afterglow identification
  14. GRB 210102B: Tiled Swift observations
  15. GRB 210104B: Swift detection of a burst
  16. GRB 210104A: Swift detection of a burst with a bright optical counterpart
  17. GRB 210102B: Tiled Swift observations
  18. Swift Trigger 1015615 is not a GRB
  19. GRB 201229A: AbAO optical afterglow detection, TSHAO optical upper limit
  20. GRB 201229A: Swift detection of a burst with a possible optical counterpart
  21. GRB 201227A: Tiled Swift observations
  22. GRB 201227A: Swift ToO observations
  23. IceCube-201222A: No Candidate Counterparts from the Zwicky Transient Facility
  24. GRB 201223A: Swift detection of a burst with a bright optical counterpart
  25. IceCube-201222A: Upper limits from a search for additional neutrino events in IceCube
  26. IceCube-201221A: Upper limits from a search for additional neutrino events in IceCube
  27. IceCube-201222A: No significant detection in HAWC
  28. IceCube-201221A: No significant detection in HAWC
  29. GRB 201221D: SMA submm observation
  30. GRB 201221D: LCOGT upper limits
  31. IceCube-201222A: not observable by Fermi-GBM
  32. GRB 201221D: Archival PS1 Imaging of the Putative Host Galaxy
  33. GRB 201221D: Lowell Discovery Telescope afterglow observations
  34. GRB 201221D: FRAM-ORM optical limit
  35. IceCube-201222A: IceCube observation of a high-energy neutrino candidate event
  36. GRB 201221D: candidate optical counterpart from the NOT
  37. GRB 201221D: Swift detection of a bright short burst
  38. Fermi GBM Sub-Threshold Detection of GRB 201221A
  39. Swift Trigger 1014012: possible GRB 201221C
  40. IceCube-201221A: not observable by Fermi-GBM
  41. IceCube-201221A: IceCube observation of a high-energy neutrino candidate event
  42. GRB 201221A: Swift detection of a burst
  43. GRB 201214A: 1.3m DFOT, optical upper limits
  44. GRB 201216C: VLT afterglow candidate discovery
  45. GRB 201216A: Swift ToO observations
  46. GRB 201214B: Swift ToO observations
  47. IceCube-201209: No significant detection in HAWC
  48. GRB 201214A: Swift ToO observations
  49. IceCube-201209A: No Candidate Counterparts from the Zwicky Transient Facility
  50. GRB 201203A: 1.3m DFOT, optical upper limits
  51. IceCube-201209A: Upper limits from a search for additional neutrino events in IceCube
  52. IceCube-201209A: Upper limits from Fermi-GBM Observations
  53. IceCube-201209A: No neutrino counterpart candidates in ANTARES search
  54. GRB 201208A: LCO observations
  55. IceCube-201209A: IceCube observation of a high-energy neutrino candidate event
  56. IceCube-201130A: Optical and NIR Imaging Follow-up by Kanata Telescope
  57. GRB 201209A: KAIT Optical Upper Limit
  58. GRB 201209A: Swift detection of a burst
  59. GRB 201208A: Swift ToO observations
  60. IceCube-201130A: No Candidate Counterparts from the Zwicky Transient Facility
  61. GRB 201203A: KAIT Optical Upper Limit
  62. GRB 201203A: Swift detection of a burst
  63. IceCube-201130A: No significant detection in HAWC
  64. IceCube-201130A: Upper limits from a search for additional neutrino events in IceCube
  65. IceCube-201130A: Not observable by Fermi-GBM
  66. GRB 201128B: Swift ToO observations
  67. IceCube-201130A: IceCube observation of a high-energy neutrino candidate event
  68. GRB 201128A: Swift detection of a burst
  69. IceCube-201114A: Updated photometry for three DECam candidate optical counterparts
  70. AMON IC_HAWC NuEm-201124A: No Neutrino Counterpart detected with ANTARES
  71. IceCube-201120A in the Cygnus region: No enhanced TeV gamma-ray flux detected by HAWC
  72. IceCube-201114A: DECam observations and candidate optical counterpart
  73. IceCube-201120A: Upper limits from a search for additional neutrino events in IceCube
  74. GRB 201015A radio afterglow with e-MERLIN
  75. IceCube-201120A: Upper limits from Fermi-GBM Observations
  76. IceCube-201120A: IceCube observation of a high-energy neutrino candidate event
  77. GRB 201116A: NOT optical observations
  78. GRB 201116A: OSN Afterglow Candidate
  79. IceCube-201115A: Upper limits from a search for additional neutrino events in IceCube
  80. IceCube-201114A: Upper limits from a search for additional neutrino events in IceCube
  81. IceCube-201115A: No significant detection in HAWC
  82. IceCube-201114A: No significant detection in HAWC
  83. GRB 201116A: Tiled Swift observations
  84. IceCube-201115A: No neutrino counterpart candidates in ANTARES search
  85. IceCube-201115A: not observable by Fermi-GBM
  86. Swift XRT observations of the Fermi-LAT source 4FGL J0658.6+0636, positionally consistent with the IceCube high-energy neutrino alert
  87. IceCube-201114A: Upper limits from Fermi GBM Observations
  88. VLASS identifies possible radio counterparts to IceCube-201115A, including a bright BL Lac candidate
  89. IceCube-201114A: No neutrino counterpart candidates in ANTARES search
  90. IceCube-201115A: IceCube observation of a high-energy neutrino candidate event
  91. IceCube-201114A - IceCube observation of a high-energy neutrino candidate event
  92. Konus-Wind detection of GRB 201105A
  93. GRB 201104A: Swift-XRT observations
  94. Swift XRT and UVOT detection of ZTF20acozryr/AT2020yxz/GRB201103B
  95. GRB 201104C: Swift ToO observations
  96. GRB 201105A: Swift detected burst and BAT refined analysis
  97. ZTF20acozryr/AT2020yxz: Zwicky Transient Facility discovery of a fast optical transient with no associated GRB
  98. GRB 201104A: Tiled Swift observations
  99. GRB 201029A: Swift detection of a burst
  100. GRB 201020A: 1.3m DFOT, optical upper limits

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