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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. GRB 240229A: VZLUSAT-2 detection
  2. Improved IPN triangulation of GRB 240227A (short)
  3. IPN triangulation of GRB 240229A
  4. GRB 240305A: Fermi GBM Final Real-time Localization
  5. Swift Trigger 1218701: Yes, we triggered on Swift J151857.0-572147 again
  6. Swift Trigger 1218696: Another trigger on Swift J151857.0-572147
  7. GRB240218A: ATCA observation of the radio counterpart
  8. Transient EPW20240219aa: Optical observations with LDT
  9. Konus-Wind detection of GRB 240303B
  10. Swift Trigger 1218645: Another detection of Swift J151857.0-572147
  11. IPN triangulation of GRB 240303B
  12. Swift J151857.0-572147: Swift-BAT refined analysis
  13. GRB 240303B: Fermi GBM Detection
  14. GRB 240225B: Swift-XRT afterglow detection
  15. Swift detection of Swift J151857.0-572147
  16. GRB 240303B: CALET Gamma-Ray Burst Monitor detection
  17. Fermi trigger No 731161136: Global MASTER-Net observations report
  18. GRB 240303C: BALROG localization (Fermi Trigger 731189113 / GRB 240303837)
  19. Swift GRB 240303A: Global MASTER-Net observations report
  20. Swift J151857.0-572147: Confirmation of a new galactic transient
  21. GRB 240215A: Swift-XRT afterglow detection
  22. GRB 240303B: BALROG localization (Fermi Trigger 731161136 / GRB 240303513)
  23. GRB 240303B: Fermi GBM Final Localization
  24. GRB 240303A: Swift detection of a burst
  25. GRB 240225B: Glowbug gamma-ray detection
  26. IceCube-240229A: Upper limits from a search for additional neutrino events in IceCube
  27. GRB 240225C: Glowbug gamma-ray detection
  28. GRB 240225A (short): Glowbug gamma-ray detection
  29. GRB 240229A: DDOTI Upper Limits on the Afterglow
  30. GRB 240218A: NOEMA upper limit
  31. GRB 240229A: CALET Gamma-Ray Burst Monitor detection
  32. IceCube-240229A - IceCube observation of a high-energy neutrino candidate track-like event
  33. Swift BAT Triggers 1218081 and 1218082 are not astrophysical
  34. GRB 240225B: further SAO RAS optical observations
  35. Fermi GRB 240229A: Global MASTER-Net observations report
  36. IceCube Alert 240229.66: Global MASTER-Net observations report
  37. GRB 240225B: Swift ToO observations
  38. Konus-Wind detection of GRB 240225B (long)
  39. GRB 240229A: BALROG localization (Fermi Trigger 730908432 / GRB 240229588)
  40. GRB 240229A: Fermi GBM Final Real-time Localization
  41. GRB 240225B: VLT/X-shooter redshift
  42. GRB 240225B : MITSuME Akeno optical afterglow candidate detection
  43. GRB 240225B: 3.6m DOT observation
  44. GRB 240225B: WINTER near-IR observations and upper limits
  45. GRB 240225B: SAO RAS optical observations
  46. GRB 240226A: GRBAlpha detection
  47. GRB 240225B: Mondy afterglow observations
  48. Fermi GRB 240227A: Global MASTER-Net observations report
  49. GRB 240225B: Liverpool Telescope afterglow observations
  50. Swift J1727.8-1613 (GRB 230824A): Madrona Peak Observatory - optical follow-up
  51. Swift Trigger 1217799 is not a GRB
  52. IPN triangulation of GRB 240227A (short)
  53. GRB 240225B: Liverpool Telescope optical afterglow observations
  54. GRB 240225B: NOT optical observations
  55. GRB 240218A: CMO SAI NIR upper limit
  56. Fermi GRB 240226A: Global MASTER-Net observations report
  57. Swift-BAT triggers 1217733 - 1217736 are not astrophysical events
  58. Swift-BAT triggers 1217729-1217732 are not astrophysical
  59. GRB 240227A: Fermi GBM Final Real-time Localization
  60. Fermi Gamma-ray Burst Monitor trigger 730618809/240226236 is not a GRB
  61. GRB 240225B: Nanshan/HMT optical afterglow detection
  62. GRB 240225B: CALET Gamma-Ray Burst Monitor detection
  63. GRB 240225B: Swift-XRT observations
  64. GRB 240226B: Fermi GBM Final Real-time Localization
  65. Transient EPW20240219aa: Kp-band imaging observations with NIRES
  66. Transient EPW20240219aa: J-band upper limits from WINTER
  67. GRB 240225C: CALET Gamma-Ray Burst Monitor detection
  68. GRB 240225B: GOTO detection of a candidate optical afterglow
  69. GRB 240226A: Fermi GBM Final Real-time Localization
  70. Transient EPW20240219aa: REM optical/NIR upper limits
  71. GRB 240225C: GRBAlpha detection
  72. GRB 240222A: ATCA radio observations
  73. Fermi trigger No 730618809: Global MASTER-Net observations report
  74. GRB 240225C: AstroSat CZTI detection
  75. GRB 240225B: AstroSat CZTI detection
  76. GRB 240225B: Tiled Swift observations
  77. GRB 240225B: MAXI/GSC detection
  78. Transient EPW20240219aa: Xinglong-2.16m optical upper limit
  79. GRB 240218A: VLA detection
  80. GRB 240225A: Swift/BAT-GUANO detection of a short burst
  81. GRB 240222A: GRBAlpha detection
  82. Transient EPW20240219aa: GECKO: LOAO Optical Upper Limits
  83. Transient EPW20240219aa: 7DT Optical Upper Limits
  84. Swift-BAT triggers 1217218-1217222 are not astrophysical
  85. VLA X-band observation of EPW20240219aa
  86. Transient EPW20240219aa: Mondy optical observations
  87. Transient EPW20240219aa: upper limit in gamma-ray range from SPI-ACS/INTEGRAL observations
  88. Insight-HXMT/HE Sub-Threshold Detection of Transient EPW20240219aa
  89. Swift BAT Sub-Threshold Detection of EPW20240219aa
  90. Transient EPW20240219aa: Liverpool Telescope non-detection and limiting magnitude
  91. GRB 240222A: GECAM detection of a burst
  92. GRB 240222A: Swift-BAT refined analysis
  93. GRB 240222A: Swift-XRT refined Analysis
  94. Swift-BAT triggers 1216907-1216911 are not astrophysical
  95. GRB 240222A: Fermi GBM Observation
  96. GRB 240222A: Swift/UVOT Upper Limits
  97. Fermi GBM Sub-Threshold Detection of EPW20240219aa as a likely GRB
  98. Swift GRB 240222A: Global MASTER-Net observations report
  99. Fermi GRB 240222A: Global MASTER-Net observations report
  100. EPW20240219aa is Likely a GRB Event

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