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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-LAT Gamma-ray Observations of IceCube-211208A
  2. IceCube-211208A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  3. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-211209A
  4. IceCube-211208A - IceCube observation of a high-energy neutrino candidate track-like event
  5. IceCube Alert 211208.84: Global MASTER-Net observations report
  6. GRB 211207A: Swift-BAT refined analysis
  7. GRB 211207A: VLT/X-shooter redshift
  8. Chandra observation of GW170817 at ~1573 days since merger (Epoch 1 of 4)
  9. GRB 211204C: Fermi GBM detection
  10. GRB 211207A: Swift-XRT refined Analysis
  11. GRB 211207A: Enhanced Swift-XRT position
  12. Swift GRB 211207A: Global MASTER-Net observations report
  13. GRB 211207A: Swift detection of a burst with an optical counterpart
  14. GRB 211206A: Not observable by Fermi-GBM
  15. GRB 211206A: AstroSat CZTI detection
  16. GRB 211206B: AstroSat CZTI detection
  17. GRB 211204C: AstroSat CZTI detection
  18. IPN triangulation of GRB 211204C
  19. GRB 211206A: Swift/BAT-GUANO detection outside the coded FOV
  20. GRB 211206A: AGILE/MCAL detection of a burst
  21. GRB 211204C: Swift/BAT-GUANO detection outside the coded FOV
  22. GRB 211204C: GECAM detection
  23. Fermi GRB 211204C: Global MASTER-Net observations report
  24. GRB 211204C: Fermi GBM Final Real-time Localization
  25. Fermi GRB 211204B: Global MASTER-Net observations report
  26. GRB 211204B: Fermi GBM Final Real-time Localization
  27. Fermi GRB 211204A: Global MASTER-Net observations report
  28. GRB 211204A: Fermi GBM Final Real-time Localization
  29. GRB 211124A: Fermi GBM Observation
  30. Swift Trigger 1086826 (possible GRB 211203A) is likely not an astrophysical event
  31. Swift GRB 211203A: Global MASTER-Net observations report
  32. Fermi GBM Upper limits for GRB 211203A
  33. Konus-Wind detection of GRB 211130A
  34. IPN triangulation of GRB 211130A
  35. GRB 211203A: Swift detection of a burst
  36. GRB 211201A: GECAM detection
  37. GRB 211201A: Swift/BAT-GUANO detection likely outside the coded FOV
  38. GRB 211106A: Second HST Observation
  39. Fermi GRB 211201A: Global MASTER-Net observations report
  40. GRB 211201A: Fermi GBM Final Real-time Localization
  41. Fermi GRB 211130A: Global MASTER-Net observations report
  42. IceCube-211125A: No significant detection in HAWC
  43. GRB 211130A: BALROG localization (Fermi Trigger 659978192 / GRB 211130636)
  44. GRB 211130A: Fermi GBM Final Real-time Localization
  45. GRB 211106A: GECAM detection
  46. GRB 211129A: Swift-BAT refined analysis
  47. GRB 211129A: Swift-XRT refined Analysis
  48. GRB 211129A: Swift/UVOT Upper Limits
  49. GRB 211106A: HST Observations
  50. GRB 211106A: Chandra Observations
  51. IceCube-Cascade 211128A: Upper limits from a search for additional neutrino events in IceCube
  52. IceCube-211125A: Upper limits from a search for additional neutrino events in IceCube
  53. GRB 211129A: Fermi GBM observation
  54. Swift GRB 211129A: Global MASTER-Net observations report
  55. GRB 211129A: Nanshan/NEXT optical upper limit
  56. GRB 211129A: Enhanced Swift-XRT position
  57. IPN triangulation of GRB 211118A
  58. GRB 211129A: MITSuME Akeno optical upper limits
  59. GRB 211129A: Swift detection of a burst
  60. IceCube-211125A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  61. GRB 211023A: Xinglong 2.16m optical observations
  62. GRB 211023A: Xinglong 2.16m optical observations
  63. Fermi-LAT Gamma-ray Observations of IceCube-211125A
  64. GRB 211120548: Fermi GBM observation
  65. Konus-Wind detection of GRB 211120A
  66. IPN triangulation of GRB 211120A
  67. IceCube-211125A: No neutrino counterpart detected with ANTARES
  68. Chandra observations of GRB 210905A
  69. IceCube-211125A: IceCube observation of a high-energy neutrino candidate track-like event
  70. GRB 211118A: Fermi GBM detection
  71. IceCube Alert 211125.27: Global MASTER-Net observations report
  72. Fermi-LAT Gamma-ray Observations of IceCube-211123A
  73. IceCube-211123A: Upper limits from a search for additional neutrino events in IceCube
  74. IceCube-211123A: INTEGRAL was inactive at the time of the event
  75. IceCube-211123A: Upper limits from Fermi-GBM Observations
  76. IceCube-211117A: not observable by Fermi-GBM
  77. IceCube-211116A: not observable by Fermi-GBM
  78. IceCube-211023A: not observable by Fermi-GBM
  79. IPN triangulation of GRB 211124A (short)
  80. HAWC-211123A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  81. HAWC-211123A: not observable by Fermi-GBM
  82. GRB 211124A: Swift/BAT-GUANO detection of a short burst outside the coded FOV
  83. IceCube Alert 211123.60: Global MASTER-Net observations report
  84. HAWC-211123A: No neutrino counterpart detected with ANTARES
  85. IceCube-211123A - IceCube observation of a high-energy neutrino candidate track-like event
  86. Fermi trigger No 659413798: Global MASTER-Net observations report
  87. Trigger_21473: Tiled Swift observations
  88. GRB 211023B: LBT likely spectroscopic redshift of the host galaxy
  89. Alert from the HAWC Burst Monitor HAWC-211123A
  90. GRB 211120A: AGILE detection
  91. GRB 211120A: AstroSat CZTI detection
  92. Fermi trigger No 659183098: Global MASTER-Net observations report
  93. Fermi trigger No 659106591: Global MASTER-Net observations report
  94. GRB 211120B: Swift/BAT-GUANO detection outside the coded FOV
  95. GRB 211120A: GECAM detection
  96. GRB 211118A: AstroSat CZTI detection
  97. GRB 211023A: optical observations and photometric evidence of supernova
  98. Fermi-LAT Gamma-ray Observations of IceCube-211117A
  99. GRB211118A: Swift/BAT-GUANO detection outside the coded FOV
  100. Fermi trigger No 658971499: Global MASTER-Net observations report

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