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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"

8295 results found.

  1. IceCube-210922A: Upper limits from Fermi-GBM Observations
  2. IceCube-210922A: No Candidate Counterparts from the Zwicky Transient Facility
  3. Konus-Wind detection of a burst from SGR 1935+2154 on 2021 September 22
  4. IceCube-210922A - IceCube observation of a high-energy neutrino candidate track-like event
  5. GRB 210919A: Swift detection of a short burst
  6. Swift trigger 1073821: detection of IGR J16418-4532
  7. GRB 210912A: BOOTES-5/JGT optical afterglow candidate (Correction to GCNC 30823)
  8. Fermi GBM observation of another bright burst in the direction of SGR 1935+2154
  9. GRB 210912A: Host-galaxy candidate in PanSTARRS
  10. GRB 210912A: BOOTES-5/JGT optical afterglow candidate
  11. Fermi GBM observation of a bright flare in the direction of SGR 1935+2154
  12. GRB 210826A: further Swift-XRT observations
  13. Swift detection of a burst from SGR Swift J1555.2-5402
  14. Fermi GBM Sub-Threshold Detection of GRB 210905A
  15. GRB 210905A: Swift detection of a burst
  16. Fermi GBM observation of a burst from SGR J1555.2-5402
  17. GRB 210901A: Swift detection of a burst
  18. GRB 210827A: further Swift-XRT observations
  19. GRB 210827A: Swift/UVOT Upper Limits
  20. GRB 210827A: Swift ToO observations
  21. GRB 210826A: Swift/UVOT Upper Limits
  22. POLAR detection of a SGR-like burst
  23. GRB 210826A: Swift-XRT observations
  24. GRB 210826A: Tiled Swift observations
  25. Swift detection of an outburst from SGR Swift J1555.2-5402
  26. GRB 210824A: Swift detection of a burst
  27. GRB 210822A: Swift detection of a burst with an optical afterglow
  28. GRB 210820A: Swift detection of a burst with an optical counterpart
  29. GRB 210818A: Swift-BAT refined analysis
  30. Konus-Wind detection of GRB 210818A
  31. GRB 210818A: Swift detection of a burst with an optical counterpart
  32. IceCube-210811A: Upper limits from a search for additional neutrino events in IceCube
  33. IceCube-210730A: not observable by Fermi-GBM
  34. IceCube-210811A: Upper limits from Fermi-GBM Observations
  35. IceCube-210811A: No Candidate Counterparts from the Zwicky Transient Facility
  36. GRB 210730A: Tautenburg observations
  37. IceCube-210811A - IceCube observation of a high-energy neutrino candidate track-like event
  38. GRB 210802A: Further Swift/XRT observation and afterglow confirmation
  39. GRB 210807C: Swift detection of a burst
  40. GRB 210807A: Swift detection of a burst with an optical counterpart
  41. GRB 210803A: Fermi GBM observation
  42. GRB 210802A: DDOTI Upper Limits
  43. GRB 210802A: Tiled Swift observations
  44. GRB 210731A: MeerLICHT optical afterglow detection
  45. GRB 210731A: Swift detection of a burst
  46. GRB 210730A: Campo Imperatore optical observations
  47. IceCube-210730A - IceCube observation of a high-energy neutrino candidate track-like event
  48. GRB 210724A: Early CAHA 2.2m limit
  49. GRB 210730A: Swift detection of a burst near M82
  50. GRB 210724A: Corrected Swift-XRT enhanced position
  51. Fermi GBM Sub-Threshold Detection of GRB 210725B
  52. GRB 210726A: Deep CAHA 2.2m limit
  53. Fermi GBM Sub-Threshold Detection of GRB 210726A
  54. GRB 210714A: Fermi GBM observation
  55. GRB 210726A: RATIR Optical Upper Limits and Candidate Host Galaxy
  56. GRB 210726A: Swift detection of a burst
  57. GRB 210724A: Zeiss-1000 of Koshka observatory, optical upper limit
  58. GRB 210724A: Afterglow candidate from OSIRIS/GTC
  59. GRB 210725B: Swift detection of a burst
  60. GRB 210725A: KAIT Optical Upper Limit
  61. GRB 210725A: Swift detection of a burst
  62. GRB 210724A: Swift detection of a burst
  63. GRB 210723A: Swift detection of a burst
  64. GRB 210722A: Swift detection of a burst with a bright optical counterpart
  65. IceCube-210717A: IceCube observation of a high-energy neutrino candidate track-like event
  66. Konus-Wind detection of GRB 210714A
  67. GRB 210712A: Swift detection of a burst
  68. GRB 210704A: Continued Gemini-North NIR K-band Detections
  69. GRB 210704A: OSIRIS/GTC Observations and Archival Detection of the Possible Host Galaxy
  70. GRB 210704A: Gemini-North Infrared Source Detection
  71. GRB 210704A: further TNG optical observations
  72. GRB 210706A: Swift/XRT afterglow confirmation
  73. Fermi GBM Sub-Threshold Detection of GRB 210708A
  74. Fermi GBM Sub-Threshold Detection of GRB 210707A
  75. IceCube-210629A - Spectroscopic observation of AT2021osi
  76. GRB 210706A: optical upper limit of Sintesz-Newton/CrAO and AS-32/AbAO
  77. GRB 210706A: Swift ToO observations
  78. GRB 210704A: RATIR optical upper limits
  79. GRB 210704A: TNG detection of the optical afterglow candidate
  80. GRB 210704A: Assy optical afterglow candidate
  81. GRB 210704A: Swift ToO observations
  82. GRB 210702A, Swift-BAT refined analysis
  83. Konus-Wind detection of GRB 210702A
  84. GRB 210702A: CALET Gamma-Ray Burst Monitor detection
  85. GRB 210702A: Swift detection of a burst with a bright optical counterpart
  86. IceCube-210629A: Upper limits from a search for additional neutrino events in IceCube
  87. IceCube-210629A: One Candidate Counterpart from the Zwicky Transient Facility
  88. IceCube-210629A: Upper limits from Fermi-GBM Observations
  89. IceCube-210629A - IceCube observation of a high-energy neutrino candidate track-like event
  90. GRB 210626A: Swift/XRT afterglow confirmation
  91. GRB 210626A: CAHA 2.2m telescope optical limit
  92. GRB 210626A: Ondrejov D50 optical limit
  93. GRB 210626A: GIT optical upper limit
  94. GRB 210626A: Swift ToO observations
  95. Fermi GBM observation of a bright burst in the direction of SGR 1935+2154
  96. GRB 210622A: Swift ToO observations
  97. Swift Trigger 1057131: detection of a burst from SGR Swift J1555.2-5402
  98. GRB 210619B: SRG/ART-XC detection
  99. GRB 210619B: Swift detection of a bright burst and optical counterpart
  100. GRB 210618A: Swift-XRT observations

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