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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 211207A: VLT/X-shooter redshift
  2. Chandra observation of GW170817 at ~1573 days since merger (Epoch 1 of 4)
  3. GRB 211204C: Fermi GBM detection
  4. GRB 211207A: Swift-XRT refined Analysis
  5. GRB 211207A: Enhanced Swift-XRT position
  6. Swift GRB 211207A: Global MASTER-Net observations report
  7. GRB 211207A: Swift detection of a burst with an optical counterpart
  8. GRB 211206A: Not observable by Fermi-GBM
  9. GRB 211206A: AstroSat CZTI detection
  10. GRB 211206B: AstroSat CZTI detection
  11. GRB 211204C: AstroSat CZTI detection
  12. IPN triangulation of GRB 211204C
  13. GRB 211206A: Swift/BAT-GUANO detection outside the coded FOV
  14. GRB 211206A: AGILE/MCAL detection of a burst
  15. GRB 211204C: Swift/BAT-GUANO detection outside the coded FOV
  16. GRB 211204C: GECAM detection
  17. Fermi GRB 211204C: Global MASTER-Net observations report
  18. GRB 211204C: Fermi GBM Final Real-time Localization
  19. Fermi GRB 211204B: Global MASTER-Net observations report
  20. GRB 211204B: Fermi GBM Final Real-time Localization
  21. Fermi GRB 211204A: Global MASTER-Net observations report
  22. GRB 211204A: Fermi GBM Final Real-time Localization
  23. GRB 211124A: Fermi GBM Observation
  24. Swift Trigger 1086826 (possible GRB 211203A) is likely not an astrophysical event
  25. Swift GRB 211203A: Global MASTER-Net observations report
  26. Fermi GBM Upper limits for GRB 211203A
  27. Konus-Wind detection of GRB 211130A
  28. IPN triangulation of GRB 211130A
  29. GRB 211203A: Swift detection of a burst
  30. GRB 211201A: GECAM detection
  31. GRB 211201A: Swift/BAT-GUANO detection likely outside the coded FOV
  32. GRB 211106A: Second HST Observation
  33. Fermi GRB 211201A: Global MASTER-Net observations report
  34. GRB 211201A: Fermi GBM Final Real-time Localization
  35. Fermi GRB 211130A: Global MASTER-Net observations report
  36. IceCube-211125A: No significant detection in HAWC
  37. GRB 211130A: BALROG localization (Fermi Trigger 659978192 / GRB 211130636)
  38. GRB 211130A: Fermi GBM Final Real-time Localization
  39. GRB 211106A: GECAM detection
  40. GRB 211129A: Swift-BAT refined analysis
  41. GRB 211129A: Swift-XRT refined Analysis
  42. GRB 211129A: Swift/UVOT Upper Limits
  43. GRB 211106A: HST Observations
  44. GRB 211106A: Chandra Observations
  45. IceCube-Cascade 211128A: Upper limits from a search for additional neutrino events in IceCube
  46. IceCube-211125A: Upper limits from a search for additional neutrino events in IceCube
  47. GRB 211129A: Fermi GBM observation
  48. Swift GRB 211129A: Global MASTER-Net observations report
  49. GRB 211129A: Nanshan/NEXT optical upper limit
  50. GRB 211129A: Enhanced Swift-XRT position
  51. IPN triangulation of GRB 211118A
  52. GRB 211129A: MITSuME Akeno optical upper limits
  53. GRB 211129A: Swift detection of a burst
  54. IceCube-211125A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  55. GRB 211023A: Xinglong 2.16m optical observations
  56. GRB 211023A: Xinglong 2.16m optical observations
  57. Fermi-LAT Gamma-ray Observations of IceCube-211125A
  58. GRB 211120548: Fermi GBM observation
  59. Konus-Wind detection of GRB 211120A
  60. IPN triangulation of GRB 211120A
  61. IceCube-211125A: No neutrino counterpart detected with ANTARES
  62. Chandra observations of GRB 210905A
  63. IceCube-211125A: IceCube observation of a high-energy neutrino candidate track-like event
  64. GRB 211118A: Fermi GBM detection
  65. IceCube Alert 211125.27: Global MASTER-Net observations report
  66. Fermi-LAT Gamma-ray Observations of IceCube-211123A
  67. IceCube-211123A: Upper limits from a search for additional neutrino events in IceCube
  68. IceCube-211123A: INTEGRAL was inactive at the time of the event
  69. IceCube-211123A: Upper limits from Fermi-GBM Observations
  70. IceCube-211117A: not observable by Fermi-GBM
  71. IceCube-211116A: not observable by Fermi-GBM
  72. IceCube-211023A: not observable by Fermi-GBM
  73. IPN triangulation of GRB 211124A (short)
  74. HAWC-211123A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  75. HAWC-211123A: not observable by Fermi-GBM
  76. GRB 211124A: Swift/BAT-GUANO detection of a short burst outside the coded FOV
  77. IceCube Alert 211123.60: Global MASTER-Net observations report
  78. HAWC-211123A: No neutrino counterpart detected with ANTARES
  79. IceCube-211123A - IceCube observation of a high-energy neutrino candidate track-like event
  80. Fermi trigger No 659413798: Global MASTER-Net observations report
  81. Trigger_21473: Tiled Swift observations
  82. GRB 211023B: LBT likely spectroscopic redshift of the host galaxy
  83. Alert from the HAWC Burst Monitor HAWC-211123A
  84. GRB 211120A: AGILE detection
  85. GRB 211120A: AstroSat CZTI detection
  86. Fermi trigger No 659183098: Global MASTER-Net observations report
  87. Fermi trigger No 659106591: Global MASTER-Net observations report
  88. GRB 211120B: Swift/BAT-GUANO detection outside the coded FOV
  89. GRB 211120A: GECAM detection
  90. GRB 211118A: AstroSat CZTI detection
  91. GRB 211023A: optical observations and photometric evidence of supernova
  92. Fermi-LAT Gamma-ray Observations of IceCube-211117A
  93. GRB211118A: Swift/BAT-GUANO detection outside the coded FOV
  94. Fermi trigger No 658971499: Global MASTER-Net observations report
  95. Search for counterpart to IceCube-211117A with ANTARES
  96. IceCube-211117A : IceCube observation of a high-energy neutrino candidate track-like event
  97. IceCube-211116A: Upper limits from a search for additional neutrino events in IceCube
  98. Fermi-LAT Gamma-ray Observations of IceCube-211116A
  99. IceCube-211116A: No neutrino counterpart detected with ANTARES
  100. IceCube Alert 211116.44: Global MASTER-Net observations report

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