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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. X-ray transient EP240315a: orphan FXT?
  2. GRB 240317A: Fermi GBM Final Real-time Localization
  3. X-ray transient EP240315a: Kinder follow-up observations for AT 2024eju with Lulin observatory
  4. X-ray transient EP240315a: GROND J-band detection
  5. X-ray transient EP240315a: VLT/X-shooter spectroscopic redshift of z = 4.859
  6. X-ray transient EP240315a: Nanshan/HMT optical upper limit
  7. Fermi trigger No 732299243: Global MASTER-Net observations report
  8. AT2024eju: followup observations with Liverpool Telescope suggest a fading transient
  9. X-ray transient EP240315a: ATLAS detection of a possible optical counterpart AT2024eju
  10. Einstein Probe detected of a fast X-ray transient EP240315a
  11. GRID detection of GRB 240306A
  12. Changes to the Fermi-GBM Triggering Thresholds
  13. Swift Triggers 1220155, 1220156, 1220157, 1220158, 1220160 and 1220161 were not astrophysical
  14. GRB 240315A: Fermi GBM Final Real-time Localization
  15. Swift Triggers 1220093, 1220094, 1220095 and 1220096 are not astrophysical
  16. Swift Triggers 1220090, 1220091 and 1220092 are not astrophysical
  17. Fermi GRB 240314A: Global MASTER-Net observations report
  18. GRB 240314A: Fermi GBM Final Real-time Localization
  19. GRB240204A: VIRT optical upper limit
  20. GRB 240312A: Glowbug gamma-ray detection
  21. Swift triggers 1219917, 1219917 and 1219922 were not astrophysical
  22. Swift Trigger 1219909 and 1219910 are not a astrophysical
  23. Swift Trigger 1219905 is not a GRB
  24. GRB 240312A: GECAM detection of a long burst
  25. Swift Trigger 1219874 is not astrophysical
  26. GRB 240303C: VZLUSAT-2 detection
  27. GRB 240310A: MASTER OT J200702.72-263928.7 inside 3sigma
  28. Fermi trigger No 731839490: Global MASTER-Net observations report
  29. Fermi-LAT gamma-ray observations of IceCube-240307A
  30. GRB 240310B: Glowbug gamma-ray detection
  31. Fermi GRB 240310A: Global MASTER-Net observations report
  32. Swift GRB240309.61: Global MASTER-Net observations report
  33. GRB 240310A: Fermi GBM Final Real-time Localization
  34. GRB 240309A: MAXI/GSC detection
  35. Swift Trigger 1219325 is not a GRB
  36. IceCube-240307A: Upper limits from a search for additional neutrino events in IceCube
  37. GRID detection of GRB 240229A (Updated Report)
  38. GRID detection of GRB 240229A
  39. GRB 240308A: Fermi GBM Final Localization
  40. Fermi trigger No 731571927: Global MASTER-Net observations report
  41. GRB 231215A: further radio observations with the VLA
  42. GRB 240306A: Fermi GBM observation
  43. IceCube-240307A - IceCube observation of a high-energy neutrino candidate track-like event
  44. GRB 240229A: Glowbug gamma-ray detection
  45. GRB 240227A (short): Glowbug gamma-ray detection
  46. IceCube Alert 240307.32: Global MASTER-Net observations report
  47. GRB 240229A: GRBAlpha detection
  48. Konus-Wind detection of GRB 231118A
  49. GRB 240306A: AstroSat CZTI detection
  50. Fermi GRB 240306A: Global MASTER-Net observations report
  51. Fermi GRB 240305A: Global MASTER-Net observations report
  52. GRB 240306A: Swift/BAT-GUANO detection of a burst
  53. GRB 240305A: Fermi GBM observation
  54. Fermi-LAT gamma-ray observations of IceCube-240229A
  55. GRB 240305C: AstroSat CZTI detection of a short burst
  56. GRB 240306A: Fermi GBM Final Real-time Localization
  57. Swift GRB240305.18: Global MASTER-Net observations report
  58. Swift GRB240305.16: Global MASTER-Net observations report
  59. Fermi GRB 240305C: Global MASTER-Net observations report
  60. GRB 240305C: Fermi GBM Final Real-time Localization
  61. GRB 240305A: Swift/BAT-GUANO arcminute localization of a burst
  62. GRB 231028C: Glowbug gamma-ray confirmation of a prior burst
  63. GRB 240218A: ALMA detection
  64. GRB 240218A: Chandra Detection and Jet Break Confirmation
  65. GRB 240305B: Fermi GBM Final Localization
  66. Fermi trigger No 731303574: Global MASTER-Net observations report
  67. Konus-Wind detection of GRB 240227A (short/hard)
  68. GRB 240303B: VZLUSAT-2 detection
  69. GRB 240229A: VZLUSAT-2 detection
  70. Improved IPN triangulation of GRB 240227A (short)
  71. IPN triangulation of GRB 240229A
  72. GRB 240305A: Fermi GBM Final Real-time Localization
  73. Swift Trigger 1218701: Yes, we triggered on Swift J151857.0-572147 again
  74. Swift Trigger 1218696: Another trigger on Swift J151857.0-572147
  75. GRB240218A: ATCA observation of the radio counterpart
  76. Transient EPW20240219aa: Optical observations with LDT
  77. Konus-Wind detection of GRB 240303B
  78. Swift Trigger 1218645: Another detection of Swift J151857.0-572147
  79. IPN triangulation of GRB 240303B
  80. Swift J151857.0-572147: Swift-BAT refined analysis
  81. GRB 240303B: Fermi GBM Detection
  82. GRB 240225B: Swift-XRT afterglow detection
  83. Swift detection of Swift J151857.0-572147
  84. GRB 240303B: CALET Gamma-Ray Burst Monitor detection
  85. Fermi trigger No 731161136: Global MASTER-Net observations report
  86. GRB 240303C: BALROG localization (Fermi Trigger 731189113 / GRB 240303837)
  87. Swift GRB 240303A: Global MASTER-Net observations report
  88. Swift J151857.0-572147: Confirmation of a new galactic transient
  89. GRB 240215A: Swift-XRT afterglow detection
  90. GRB 240303B: BALROG localization (Fermi Trigger 731161136 / GRB 240303513)
  91. GRB 240303B: Fermi GBM Final Localization
  92. GRB 240303A: Swift detection of a burst
  93. GRB 240225B: Glowbug gamma-ray detection
  94. IceCube-240229A: Upper limits from a search for additional neutrino events in IceCube
  95. GRB 240225C: Glowbug gamma-ray detection
  96. GRB 240225A (short): Glowbug gamma-ray detection
  97. GRB 240229A: DDOTI Upper Limits on the Afterglow
  98. GRB 240218A: NOEMA upper limit
  99. GRB 240229A: CALET Gamma-Ray Burst Monitor detection
  100. IceCube-240229A - IceCube observation of a high-energy neutrino candidate track-like event

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