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

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