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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"

7452 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. Continued Chandra observations of GW170817 at ~3.3 years since merger
  5. GRB 210120A : 1.3m DFOT optical observations
  6. GRB 210120A(MASTER OT J105242.66+152355.0 / AT2021axc): Mondy optical observations
  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. NuEm-210111A : No neutrino counterpart in ANTARES
  10. GRB 210112A: Kitab a optical upper limit
  11. GRB 210112A: Swift detection of a burst with an optical counterpart
  12. GRB 210102B: Assy optical afterglow identification
  13. GW170817: HST observations at 3.4 years from merger
  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. GRB 201229A: AbAO optical afterglow detection, TSHAO optical upper limit
  19. GRB 201229A: Swift detection of a burst with a possible optical counterpart
  20. GRB 201227A: Tiled Swift observations
  21. GRB 201227A: Swift ToO observations
  22. IceCube-201222A: No Candidate Counterparts from the Zwicky Transient Facility
  23. GRB 201223A: Swift detection of a burst with a bright optical counterpart
  24. GRB 201221D: SMA submm observation
  25. GRB 201221D: LCOGT upper limits
  26. IceCube-201222A: not observable by Fermi-GBM
  27. GRB 201221D: Archival PS1 Imaging of the Putative Host Galaxy
  28. GRB 201221D: Lowell Discovery Telescope afterglow observations
  29. GRB 201221D: FRAM-ORM optical limit
  30. IceCube-201222A: IceCube observation of a high-energy neutrino candidate event
  31. GRB 201221D: candidate optical counterpart from the NOT
  32. GRB 201221D: Swift detection of a bright short burst
  33. Swift Trigger 1014012: possible GRB 201221C
  34. IceCube-201221A: not observable by Fermi-GBM
  35. IceCube-201221A: IceCube observation of a high-energy neutrino candidate event
  36. GRB 201221A: Swift detection of a burst
  37. GRB 201214A: 1.3m DFOT, optical upper limits
  38. GRB 201216C: VLT afterglow candidate discovery
  39. GRB 201216A: Swift ToO observations
  40. Chandra observations of GW170817 at ~3.3 years since merger (Full report)
  41. VLA observations of GW170817 at ~3.3 years post-merger
  42. GRB 201214B: Swift ToO observations
  43. Potential X-ray KN afterglow from Chandra observations of GW170817 ~3.3 years since merger (3 Epochs of 4)
  44. GRB 201214A: Swift ToO observations
  45. IceCube-201209A: No Candidate Counterparts from the Zwicky Transient Facility
  46. GRB 201203A: 1.3m DFOT, optical upper limits
  47. IceCube-201209A: Upper limits from Fermi-GBM Observations
  48. IceCube-201209A: No neutrino counterpart candidates in ANTARES search
  49. Chandra observations of GW170817 at ~3.3 years since merger (Observation 1 of 4)
  50. GRB 201208A: LCO observations
  51. IceCube-201209A: IceCube observation of a high-energy neutrino candidate event
  52. IceCube-201130A: Optical and NIR Imaging Follow-up by Kanata Telescope
  53. GRB 201209A: KAIT Optical Upper Limit
  54. GRB 201209A: Swift detection of a burst
  55. GRB 201208A: Swift ToO observations
  56. IceCube-201130A: No Candidate Counterparts from the Zwicky Transient Facility
  57. GRB 201203A: KAIT Optical Upper Limit
  58. GRB 201203A: Swift detection of a burst
  59. IceCube-201130A: Not observable by Fermi-GBM
  60. GRB 201128B: Swift ToO observations
  61. IceCube-201130A: IceCube observation of a high-energy neutrino candidate event
  62. GRB 201128A: Swift detection of a burst
  63. IceCube-201114A: Updated photometry for three DECam candidate optical counterparts
  64. AMON IC_HAWC NuEm-201124A: No Neutrino Counterpart detected with ANTARES
  65. IceCube-201114A: DECam observations and candidate optical counterpart
  66. IceCube-201120A: Upper limits from Fermi-GBM Observations
  67. IceCube-201120A: IceCube observation of a high-energy neutrino candidate event
  68. GRB 201116A: NOT optical observations
  69. GRB 201116A: OSN Afterglow Candidate
  70. Swift Trigger 1006917 is Be/X-ray binary pulsar 1A 0535+262
  71. GRB 201116A: Tiled Swift observations
  72. IceCube-201115A: No neutrino counterpart candidates in ANTARES search
  73. IceCube-201115A: not observable by Fermi-GBM
  74. Swift XRT observations of the Fermi-LAT source 4FGL J0658.6+0636, positionally consistent with the IceCube high-energy neutrino alert
  75. IceCube-201114A: Upper limits from Fermi GBM Observations
  76. VLASS identifies possible radio counterparts to IceCube-201115A, including a bright BL Lac candidate
  77. IceCube-201114A: No neutrino counterpart candidates in ANTARES search
  78. IceCube-201115A: IceCube observation of a high-energy neutrino candidate event
  79. IceCube-201114A - IceCube observation of a high-energy neutrino candidate event
  80. GRB 201104A: Swift-XRT observations
  81. Swift XRT and UVOT detection of ZTF20acozryr/AT2020yxz/GRB201103B
  82. GRB 201104C: Swift ToO observations
  83. ZTF20acozryr/AT2020yxz: Zwicky Transient Facility discovery of a fast optical transient with no associated GRB
  84. GRB 201104A: Tiled Swift observations
  85. GRB 201029A: Swift detection of a burst
  86. GRB 201020A: 1.3m DFOT, optical upper limits
  87. GRB 201027A: Swift detection of a burst
  88. GRB 201026A: Swift detection of a burst
  89. GRB 201024A: Swift detection of a burst with an optical afterglow
  90. IceCube-201021A: One candidate counterpart from the Zwicky Transient Facility
  91. Fermi-LAT Gamma-ray Observations of IceCube-201021A and detection of a new gamma-ray source, Fermi J1725.5+1312
  92. GRB 201014A: 2.0m HCT upper limit
  93. IceCube-201021A: No neutrino counterpart candidates in ANTARES search
  94. IceCube-201021A: Upper limits from Fermi-GBM Observations
  95. GRB 201021C: Swift detection of a burst with an optical counterpart
  96. HAWC-201019A: No Neutrino Counterpart detected with ANTARES
  97. GRB200826A: GMOS-N detection of a supernova bump
  98. GRB 201020B: Swift ToO observations
  99. IceCube-201021A: IceCube observation of a high-energy neutrino candidate event
  100. GRB 201020A: Swift detection of a burst with an optical counterpart.

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