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

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