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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 211211A: Global MASTER-Net observations report
  2. GRB 211211A: Enhanced Swift-XRT position
  3. GRB 211207A: Swift/UVOT Detection
  4. GRB 211211A: KAIT Optical Afterglow Candidate
  5. GRB 211211A: Swift detection of a bright burst
  6. GRB 211211A: Fermi GBM Final Real-time Localization
  7. Fermi trigger No 660868196: Global MASTER-Net observations report
  8. IceCube-211208A: No significant detection in HAWC
  9. AMON NuEm-211020A: No neutrino counterpart detected with ANTARES
  10. Fermi trigger No 660736561: Global MASTER-Net observations report
  11. GRB 211130A: MeerLICHT identification of possible afterglow candidate
  12. IceCube-211208A: Upper limits from a search for additional neutrino events in IceCube
  13. Fermi-LAT Gamma-ray Observations of IceCube-211208A
  14. IceCube-211208A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  15. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-211209A
  16. IceCube-211208A - IceCube observation of a high-energy neutrino candidate track-like event
  17. IceCube Alert 211208.84: Global MASTER-Net observations report
  18. GRB 211207A: Swift-BAT refined analysis
  19. GRB 211207A: VLT/X-shooter redshift
  20. Chandra observation of GW170817 at ~1573 days since merger (Epoch 1 of 4)
  21. GRB 211204C: Fermi GBM detection
  22. GRB 211207A: Swift-XRT refined Analysis
  23. GRB 211207A: Enhanced Swift-XRT position
  24. Swift GRB 211207A: Global MASTER-Net observations report
  25. GRB 211207A: Swift detection of a burst with an optical counterpart
  26. GRB 211206A: Not observable by Fermi-GBM
  27. GRB 211206A: AstroSat CZTI detection
  28. GRB 211206B: AstroSat CZTI detection
  29. GRB 211204C: AstroSat CZTI detection
  30. IPN triangulation of GRB 211204C
  31. GRB 211206A: Swift/BAT-GUANO detection outside the coded FOV
  32. GRB 211206A: AGILE/MCAL detection of a burst
  33. GRB 211204C: Swift/BAT-GUANO detection outside the coded FOV
  34. GRB 211204C: GECAM detection
  35. Fermi GRB 211204C: Global MASTER-Net observations report
  36. GRB 211204C: Fermi GBM Final Real-time Localization
  37. Fermi GRB 211204B: Global MASTER-Net observations report
  38. GRB 211204B: Fermi GBM Final Real-time Localization
  39. Fermi GRB 211204A: Global MASTER-Net observations report
  40. GRB 211204A: Fermi GBM Final Real-time Localization
  41. GRB 211124A: Fermi GBM Observation
  42. Swift Trigger 1086826 (possible GRB 211203A) is likely not an astrophysical event
  43. Swift GRB 211203A: Global MASTER-Net observations report
  44. Fermi GBM Upper limits for GRB 211203A
  45. Konus-Wind detection of GRB 211130A
  46. IPN triangulation of GRB 211130A
  47. GRB 211203A: Swift detection of a burst
  48. GRB 211201A: GECAM detection
  49. GRB 211201A: Swift/BAT-GUANO detection likely outside the coded FOV
  50. GRB 211106A: Second HST Observation
  51. Fermi GRB 211201A: Global MASTER-Net observations report
  52. GRB 211201A: Fermi GBM Final Real-time Localization
  53. Fermi GRB 211130A: Global MASTER-Net observations report
  54. IceCube-211125A: No significant detection in HAWC
  55. GRB 211130A: BALROG localization (Fermi Trigger 659978192 / GRB 211130636)
  56. GRB 211130A: Fermi GBM Final Real-time Localization
  57. GRB 211106A: GECAM detection
  58. GRB 211129A: Swift-BAT refined analysis
  59. GRB 211129A: Swift-XRT refined Analysis
  60. GRB 211129A: Swift/UVOT Upper Limits
  61. GRB 211106A: HST Observations
  62. GRB 211106A: Chandra Observations
  63. IceCube-Cascade 211128A: Upper limits from a search for additional neutrino events in IceCube
  64. IceCube-211125A: Upper limits from a search for additional neutrino events in IceCube
  65. GRB 211129A: Fermi GBM observation
  66. Swift GRB 211129A: Global MASTER-Net observations report
  67. GRB 211129A: Nanshan/NEXT optical upper limit
  68. GRB 211129A: Enhanced Swift-XRT position
  69. IPN triangulation of GRB 211118A
  70. GRB 211129A: MITSuME Akeno optical upper limits
  71. GRB 211129A: Swift detection of a burst
  72. IceCube-211125A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  73. GRB 211023A: Xinglong 2.16m optical observations
  74. GRB 211023A: Xinglong 2.16m optical observations
  75. Fermi-LAT Gamma-ray Observations of IceCube-211125A
  76. GRB 211120548: Fermi GBM observation
  77. Konus-Wind detection of GRB 211120A
  78. IPN triangulation of GRB 211120A
  79. IceCube-211125A: No neutrino counterpart detected with ANTARES
  80. Chandra observations of GRB 210905A
  81. IceCube-211125A: IceCube observation of a high-energy neutrino candidate track-like event
  82. GRB 211118A: Fermi GBM detection
  83. IceCube Alert 211125.27: Global MASTER-Net observations report
  84. Fermi-LAT Gamma-ray Observations of IceCube-211123A
  85. IceCube-211123A: Upper limits from a search for additional neutrino events in IceCube
  86. IceCube-211123A: INTEGRAL was inactive at the time of the event
  87. IceCube-211123A: Upper limits from Fermi-GBM Observations
  88. IceCube-211117A: not observable by Fermi-GBM
  89. IceCube-211116A: not observable by Fermi-GBM
  90. IceCube-211023A: not observable by Fermi-GBM
  91. IPN triangulation of GRB 211124A (short)
  92. HAWC-211123A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  93. HAWC-211123A: not observable by Fermi-GBM
  94. GRB 211124A: Swift/BAT-GUANO detection of a short burst outside the coded FOV
  95. IceCube Alert 211123.60: Global MASTER-Net observations report
  96. HAWC-211123A: No neutrino counterpart detected with ANTARES
  97. IceCube-211123A - IceCube observation of a high-energy neutrino candidate track-like event
  98. Fermi trigger No 659413798: Global MASTER-Net observations report
  99. Trigger_21473: Tiled Swift observations
  100. GRB 211023B: LBT likely spectroscopic redshift of the host galaxy

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