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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 240303A: Swift detection of a burst
  2. GRB 240225B: Glowbug gamma-ray detection
  3. IceCube-240229A: Upper limits from a search for additional neutrino events in IceCube
  4. GRB 240225C: Glowbug gamma-ray detection
  5. GRB 240225A (short): Glowbug gamma-ray detection
  6. GRB 240229A: DDOTI Upper Limits on the Afterglow
  7. GRB 240218A: NOEMA upper limit
  8. GRB 240229A: CALET Gamma-Ray Burst Monitor detection
  9. IceCube-240229A - IceCube observation of a high-energy neutrino candidate track-like event
  10. Swift BAT Triggers 1218081 and 1218082 are not astrophysical
  11. GRB 240225B: further SAO RAS optical observations
  12. Fermi GRB 240229A: Global MASTER-Net observations report
  13. IceCube Alert 240229.66: Global MASTER-Net observations report
  14. GRB 240225B: Swift ToO observations
  15. Konus-Wind detection of GRB 240225B (long)
  16. GRB 240229A: BALROG localization (Fermi Trigger 730908432 / GRB 240229588)
  17. GRB 240229A: Fermi GBM Final Real-time Localization
  18. GRB 240225B: VLT/X-shooter redshift
  19. GRB 240225B : MITSuME Akeno optical afterglow candidate detection
  20. GRB 240225B: 3.6m DOT observation
  21. GRB 240225B: WINTER near-IR observations and upper limits
  22. GRB 240225B: SAO RAS optical observations
  23. GRB 240226A: GRBAlpha detection
  24. GRB 240225B: Mondy afterglow observations
  25. Fermi GRB 240227A: Global MASTER-Net observations report
  26. GRB 240225B: Liverpool Telescope afterglow observations
  27. Swift J1727.8-1613 (GRB 230824A): Madrona Peak Observatory - optical follow-up
  28. Swift Trigger 1217799 is not a GRB
  29. IPN triangulation of GRB 240227A (short)
  30. GRB 240225B: Liverpool Telescope optical afterglow observations
  31. GRB 240225B: NOT optical observations
  32. GRB 240218A: CMO SAI NIR upper limit
  33. Fermi GRB 240226A: Global MASTER-Net observations report
  34. Swift-BAT triggers 1217733 - 1217736 are not astrophysical events
  35. Swift-BAT triggers 1217729-1217732 are not astrophysical
  36. GRB 240227A: Fermi GBM Final Real-time Localization
  37. Fermi Gamma-ray Burst Monitor trigger 730618809/240226236 is not a GRB
  38. GRB 240225B: Nanshan/HMT optical afterglow detection
  39. GRB 240225B: CALET Gamma-Ray Burst Monitor detection
  40. GRB 240225B: Swift-XRT observations
  41. GRB 240226B: Fermi GBM Final Real-time Localization
  42. Transient EPW20240219aa: Kp-band imaging observations with NIRES
  43. Transient EPW20240219aa: J-band upper limits from WINTER
  44. GRB 240225C: CALET Gamma-Ray Burst Monitor detection
  45. GRB 240225B: GOTO detection of a candidate optical afterglow
  46. GRB 240226A: Fermi GBM Final Real-time Localization
  47. Transient EPW20240219aa: REM optical/NIR upper limits
  48. GRB 240225C: GRBAlpha detection
  49. GRB 240222A: ATCA radio observations
  50. Fermi trigger No 730618809: Global MASTER-Net observations report
  51. GRB 240225C: AstroSat CZTI detection
  52. GRB 240225B: AstroSat CZTI detection
  53. GRB 240225B: Tiled Swift observations
  54. GRB 240225B: MAXI/GSC detection
  55. Transient EPW20240219aa: Xinglong-2.16m optical upper limit
  56. GRB 240218A: VLA detection
  57. GRB 240225A: Swift/BAT-GUANO detection of a short burst
  58. GRB 240222A: GRBAlpha detection
  59. Transient EPW20240219aa: GECKO: LOAO Optical Upper Limits
  60. Transient EPW20240219aa: 7DT Optical Upper Limits
  61. Swift-BAT triggers 1217218-1217222 are not astrophysical
  62. VLA X-band observation of EPW20240219aa
  63. Transient EPW20240219aa: Mondy optical observations
  64. Transient EPW20240219aa: upper limit in gamma-ray range from SPI-ACS/INTEGRAL observations
  65. Insight-HXMT/HE Sub-Threshold Detection of Transient EPW20240219aa
  66. Swift BAT Sub-Threshold Detection of EPW20240219aa
  67. Transient EPW20240219aa: Liverpool Telescope non-detection and limiting magnitude
  68. GRB 240222A: GECAM detection of a burst
  69. GRB 240222A: Swift-BAT refined analysis
  70. GRB 240222A: Swift-XRT refined Analysis
  71. Swift-BAT triggers 1216907-1216911 are not astrophysical
  72. GRB 240222A: Fermi GBM Observation
  73. GRB 240222A: Swift/UVOT Upper Limits
  74. Fermi GBM Sub-Threshold Detection of EPW20240219aa as a likely GRB
  75. Swift GRB 240222A: Global MASTER-Net observations report
  76. Fermi GRB 240222A: Global MASTER-Net observations report
  77. EPW20240219aa is Likely a GRB Event
  78. Swift Trigger 1216864 is not an astrophysical event
  79. GRB 240222A: REM optical and NIR early-time observations
  80. GRB 240222A: Swift detection of a burst
  81. GRB 240222A: Fermi GBM Final Real-time Localization
  82. Swift-BAT triggers 1216751 and 1216753 are not astrophysical events
  83. Swift-BAT triggers 1216743-1216748 are not astrophysical
  84. Swift GRB240221.92: Global MASTER-Net observations report
  85. GRB 240218A: MeerLICHT upper limits
  86. GRB 240216A: Glowbug gamma-ray detection
  87. GRB 240215B: Fermi GBM Observation
  88. GRB 240218A: LBT H-band detection
  89. GRB 240218A: Swift-BAT refined analysis
  90. Fermi GRB 240220A: Global MASTER-Net observations report
  91. GRB 240220A: Fermi GBM Final Real-time Localization
  92. Konus-Wind detection of GRB 240218A
  93. GRB 240218A: Swift-XRT refined Analysis
  94. GRB 240218A: VLT/X-shooter redshift of z = 6.782
  95. GRB 240218A: Fermi GBM Detection
  96. GRB 240215A: Fermi GBM Observation
  97. GRB 240216A: GRBAlpha detection
  98. GRB 240215B: GRBAlpha detection
  99. IPN triangulation of GRB 240209A
  100. Fermi trigger No 729914426: Global MASTER-Net observations report

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