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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"

7448 results found.

  1. GRB 210120A : 1.3m DFOT optical observations
  2. GRB 210120A(MASTER OT J105242.66+152355.0 / AT2021axc): Mondy optical observations
  3. GECAM detection of a short GRB 210119A or a new SGR candidate Swift J1851.2-6148
  4. GRB 210112A: 1.3m DFOT Optical upper limit
  5. NuEm-210111A : No neutrino counterpart in ANTARES
  6. GRB 210112A: Kitab a optical upper limit
  7. GRB 210112A: Swift detection of a burst with an optical counterpart
  8. GRB 210102B: Assy optical afterglow identification
  9. GW170817: HST observations at 3.4 years from merger
  10. GRB 210102B: Tiled Swift observations
  11. GRB 210104B: Swift detection of a burst
  12. GRB 210104A: Swift detection of a burst with a bright optical counterpart
  13. GRB 210102B: Tiled Swift observations
  14. GRB 201229A: AbAO optical afterglow detection, TSHAO optical upper limit
  15. GRB 201229A: Swift detection of a burst with a possible optical counterpart
  16. GRB 201227A: Tiled Swift observations
  17. GRB 201227A: Swift ToO observations
  18. IceCube-201222A: No Candidate Counterparts from the Zwicky Transient Facility
  19. GRB 201223A: Swift detection of a burst with a bright optical counterpart
  20. GRB 201221D: SMA submm observation
  21. GRB 201221D: LCOGT upper limits
  22. IceCube-201222A: not observable by Fermi-GBM
  23. GRB 201221D: Archival PS1 Imaging of the Putative Host Galaxy
  24. GRB 201221D: Lowell Discovery Telescope afterglow observations
  25. GRB 201221D: FRAM-ORM optical limit
  26. IceCube-201222A: IceCube observation of a high-energy neutrino candidate event
  27. GRB 201221D: candidate optical counterpart from the NOT
  28. GRB 201221D: Swift detection of a bright short burst
  29. Swift Trigger 1014012: possible GRB 201221C
  30. IceCube-201221A: not observable by Fermi-GBM
  31. IceCube-201221A: IceCube observation of a high-energy neutrino candidate event
  32. GRB 201221A: Swift detection of a burst
  33. GRB 201214A: 1.3m DFOT, optical upper limits
  34. GRB 201216C: VLT afterglow candidate discovery
  35. GRB 201216A: Swift ToO observations
  36. Chandra observations of GW170817 at ~3.3 years since merger (Full report)
  37. VLA observations of GW170817 at ~3.3 years post-merger
  38. GRB 201214B: Swift ToO observations
  39. Potential X-ray KN afterglow from Chandra observations of GW170817 ~3.3 years since merger (3 Epochs of 4)
  40. GRB 201214A: Swift ToO observations
  41. IceCube-201209A: No Candidate Counterparts from the Zwicky Transient Facility
  42. GRB 201203A: 1.3m DFOT, optical upper limits
  43. IceCube-201209A: Upper limits from Fermi-GBM Observations
  44. IceCube-201209A: No neutrino counterpart candidates in ANTARES search
  45. Chandra observations of GW170817 at ~3.3 years since merger (Observation 1 of 4)
  46. GRB 201208A: LCO observations
  47. IceCube-201209A: IceCube observation of a high-energy neutrino candidate event
  48. IceCube-201130A: Optical and NIR Imaging Follow-up by Kanata Telescope
  49. GRB 201209A: KAIT Optical Upper Limit
  50. GRB 201209A: Swift detection of a burst
  51. GRB 201208A: Swift ToO observations
  52. IceCube-201130A: No Candidate Counterparts from the Zwicky Transient Facility
  53. GRB 201203A: KAIT Optical Upper Limit
  54. GRB 201203A: Swift detection of a burst
  55. IceCube-201130A: Not observable by Fermi-GBM
  56. GRB 201128B: Swift ToO observations
  57. IceCube-201130A: IceCube observation of a high-energy neutrino candidate event
  58. GRB 201128A: Swift detection of a burst
  59. IceCube-201114A: Updated photometry for three DECam candidate optical counterparts
  60. AMON IC_HAWC NuEm-201124A: No Neutrino Counterpart detected with ANTARES
  61. IceCube-201114A: DECam observations and candidate optical counterpart
  62. IceCube-201120A: Upper limits from Fermi-GBM Observations
  63. IceCube-201120A: IceCube observation of a high-energy neutrino candidate event
  64. GRB 201116A: NOT optical observations
  65. GRB 201116A: OSN Afterglow Candidate
  66. Swift Trigger 1006917 is Be/X-ray binary pulsar 1A 0535+262
  67. GRB 201116A: Tiled Swift observations
  68. IceCube-201115A: No neutrino counterpart candidates in ANTARES search
  69. IceCube-201115A: not observable by Fermi-GBM
  70. Swift XRT observations of the Fermi-LAT source 4FGL J0658.6+0636, positionally consistent with the IceCube high-energy neutrino alert
  71. IceCube-201114A: Upper limits from Fermi GBM Observations
  72. VLASS identifies possible radio counterparts to IceCube-201115A, including a bright BL Lac candidate
  73. IceCube-201114A: No neutrino counterpart candidates in ANTARES search
  74. IceCube-201115A: IceCube observation of a high-energy neutrino candidate event
  75. IceCube-201114A - IceCube observation of a high-energy neutrino candidate event
  76. GRB 201104A: Swift-XRT observations
  77. Swift XRT and UVOT detection of ZTF20acozryr/AT2020yxz/GRB201103B
  78. GRB 201104C: Swift ToO observations
  79. ZTF20acozryr/AT2020yxz: Zwicky Transient Facility discovery of a fast optical transient with no associated GRB
  80. GRB 201104A: Tiled Swift observations
  81. GRB 201029A: Swift detection of a burst
  82. GRB 201020A: 1.3m DFOT, optical upper limits
  83. GRB 201027A: Swift detection of a burst
  84. GRB 201026A: Swift detection of a burst
  85. GRB 201024A: Swift detection of a burst with an optical afterglow
  86. IceCube-201021A: One candidate counterpart from the Zwicky Transient Facility
  87. Fermi-LAT Gamma-ray Observations of IceCube-201021A and detection of a new gamma-ray source, Fermi J1725.5+1312
  88. GRB 201014A: 2.0m HCT upper limit
  89. IceCube-201021A: No neutrino counterpart candidates in ANTARES search
  90. IceCube-201021A: Upper limits from Fermi-GBM Observations
  91. GRB 201021C: Swift detection of a burst with an optical counterpart
  92. HAWC-201019A: No Neutrino Counterpart detected with ANTARES
  93. GRB200826A: GMOS-N detection of a supernova bump
  94. GRB 201020B: Swift ToO observations
  95. IceCube-201021A: IceCube observation of a high-energy neutrino candidate event
  96. GRB 201020A: Swift detection of a burst with an optical counterpart.
  97. GRB 201015A: 6 GHz VLA radio afterglow candidate detection
  98. GRB 201013A: 3.6m DOT Optical Observations
  99. GRB 201017A: Assy and Mondy optical observations, possible afterglow detection
  100. GRB 201017A: Swift detection of a burst

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