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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. Fermi GRB 240229A: Global MASTER-Net observations report
  2. IceCube Alert 240229.66: Global MASTER-Net observations report
  3. GRB 240225B: Swift ToO observations
  4. Konus-Wind detection of GRB 240225B (long)
  5. GRB 240229A: BALROG localization (Fermi Trigger 730908432 / GRB 240229588)
  6. GRB 240229A: Fermi GBM Final Real-time Localization
  7. GRB 240225B: VLT/X-shooter redshift
  8. GRB 240225B : MITSuME Akeno optical afterglow candidate detection
  9. GRB 240225B: 3.6m DOT observation
  10. GRB 240225B: WINTER near-IR observations and upper limits
  11. GRB 240225B: SAO RAS optical observations
  12. GRB 240226A: GRBAlpha detection
  13. GRB 240225B: Mondy afterglow observations
  14. Fermi GRB 240227A: Global MASTER-Net observations report
  15. GRB 240225B: Liverpool Telescope afterglow observations
  16. Swift J1727.8-1613 (GRB 230824A): Madrona Peak Observatory - optical follow-up
  17. Swift Trigger 1217799 is not a GRB
  18. IPN triangulation of GRB 240227A (short)
  19. GRB 240225B: Liverpool Telescope optical afterglow observations
  20. GRB 240225B: NOT optical observations
  21. GRB 240218A: CMO SAI NIR upper limit
  22. Fermi GRB 240226A: Global MASTER-Net observations report
  23. Swift-BAT triggers 1217733 - 1217736 are not astrophysical events
  24. Swift-BAT triggers 1217729-1217732 are not astrophysical
  25. GRB 240227A: Fermi GBM Final Real-time Localization
  26. Fermi Gamma-ray Burst Monitor trigger 730618809/240226236 is not a GRB
  27. GRB 240225B: Nanshan/HMT optical afterglow detection
  28. GRB 240225B: CALET Gamma-Ray Burst Monitor detection
  29. GRB 240225B: Swift-XRT observations
  30. GRB 240226B: Fermi GBM Final Real-time Localization
  31. Transient EPW20240219aa: Kp-band imaging observations with NIRES
  32. Transient EPW20240219aa: J-band upper limits from WINTER
  33. GRB 240225C: CALET Gamma-Ray Burst Monitor detection
  34. GRB 240225B: GOTO detection of a candidate optical afterglow
  35. GRB 240226A: Fermi GBM Final Real-time Localization
  36. Transient EPW20240219aa: REM optical/NIR upper limits
  37. GRB 240225C: GRBAlpha detection
  38. GRB 240222A: ATCA radio observations
  39. Fermi trigger No 730618809: Global MASTER-Net observations report
  40. GRB 240225C: AstroSat CZTI detection
  41. GRB 240225B: AstroSat CZTI detection
  42. GRB 240225B: Tiled Swift observations
  43. GRB 240225B: MAXI/GSC detection
  44. Transient EPW20240219aa: Xinglong-2.16m optical upper limit
  45. GRB 240218A: VLA detection
  46. GRB 240225A: Swift/BAT-GUANO detection of a short burst
  47. GRB 240222A: GRBAlpha detection
  48. Transient EPW20240219aa: GECKO: LOAO Optical Upper Limits
  49. Transient EPW20240219aa: 7DT Optical Upper Limits
  50. Swift-BAT triggers 1217218-1217222 are not astrophysical
  51. VLA X-band observation of EPW20240219aa
  52. Transient EPW20240219aa: Mondy optical observations
  53. Transient EPW20240219aa: upper limit in gamma-ray range from SPI-ACS/INTEGRAL observations
  54. Insight-HXMT/HE Sub-Threshold Detection of Transient EPW20240219aa
  55. Swift BAT Sub-Threshold Detection of EPW20240219aa
  56. Transient EPW20240219aa: Liverpool Telescope non-detection and limiting magnitude
  57. GRB 240222A: GECAM detection of a burst
  58. GRB 240222A: Swift-BAT refined analysis
  59. GRB 240222A: Swift-XRT refined Analysis
  60. Swift-BAT triggers 1216907-1216911 are not astrophysical
  61. GRB 240222A: Fermi GBM Observation
  62. GRB 240222A: Swift/UVOT Upper Limits
  63. Fermi GBM Sub-Threshold Detection of EPW20240219aa as a likely GRB
  64. Swift GRB 240222A: Global MASTER-Net observations report
  65. Fermi GRB 240222A: Global MASTER-Net observations report
  66. EPW20240219aa is Likely a GRB Event
  67. Swift Trigger 1216864 is not an astrophysical event
  68. GRB 240222A: REM optical and NIR early-time observations
  69. GRB 240222A: Swift detection of a burst
  70. GRB 240222A: Fermi GBM Final Real-time Localization
  71. Swift-BAT triggers 1216751 and 1216753 are not astrophysical events
  72. Swift-BAT triggers 1216743-1216748 are not astrophysical
  73. Swift GRB240221.92: Global MASTER-Net observations report
  74. GRB 240218A: MeerLICHT upper limits
  75. GRB 240216A: Glowbug gamma-ray detection
  76. GRB 240215B: Fermi GBM Observation
  77. GRB 240218A: LBT H-band detection
  78. GRB 240218A: Swift-BAT refined analysis
  79. Fermi GRB 240220A: Global MASTER-Net observations report
  80. GRB 240220A: Fermi GBM Final Real-time Localization
  81. Konus-Wind detection of GRB 240218A
  82. GRB 240218A: Swift-XRT refined Analysis
  83. GRB 240218A: VLT/X-shooter redshift of z = 6.782
  84. GRB 240218A: Fermi GBM Detection
  85. GRB 240215A: Fermi GBM Observation
  86. GRB 240216A: GRBAlpha detection
  87. GRB 240215B: GRBAlpha detection
  88. IPN triangulation of GRB 240209A
  89. Fermi trigger No 729914426: Global MASTER-Net observations report
  90. GRB 240218A: VLT/FORS2 z-band detection
  91. GRB 240218A: Enhanced Swift-XRT position
  92. GRB 240218A: REM detection of a NIR afterglow candidate
  93. Gamma-ray flaring activity from the blazar 1ES 1959+650 observed by the Fermi-LAT
  94. GRB 240213A: GRBAlpha detection
  95. GRB 240218A : r-band upper limit from Observatoire de Haute-Provence
  96. GRB240218A: VLT/X-shooter upper limits
  97. GRB 240218A: Swift detection of a burst
  98. Swift GRB240218.08: Global MASTER-Net observations report
  99. GRB 240215C: Fermi GBM Final Real-time Localization
  100. GRB 240215B: Swift/BAT-GUANO detection of a burst outside the coded FOV

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