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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: HCT and GIT optical follow up observations
  2. GRB 211211A: CALET Gamma-Ray Burst Monitor detection
  3. IceCube-211208A: No neutrino counterpart detected with ANTARES
  4. Fermi GRB 211212A: Global MASTER-Net observations report
  5. GRB 211211A: incorrect E_iso value in GCN 31221
  6. GRB 211211A: Swift/UVOT detection
  7. GRB 211211A: NOT optical spectroscopy
  8. GRB 211211B: GECAM detection
  9. Fermi GRB 211212B: Global MASTER-Net observations report
  10. GRB 211211A: Afterglow detection from CAFOS/2.2m CAHA
  11. GRB 211211A: MITSuME Akeno optical observation
  12. Swift GRB 211211A: Global MASTER-Net observations report
  13. GRB 211212B: Fermi GBM Final Real-time Localization
  14. GRB 211211A: LCO Optical Observations
  15. GRB 211211A: Nanshan/NEXT optical observations
  16. GRB 211211A: Swift-XRT refined Analysis
  17. GRB 211212A: Fermi GBM Final Real-time Localization
  18. GRB 211211A: Fermi GBM observation
  19. GRB 211211A: Swift-BAT refined analysis
  20. Fermi GRB 211211B: Global MASTER-Net observations report
  21. GRB 211211B: Fermi GBM Final Real-time Localization
  22. Fermi GRB 211211A: Global MASTER-Net observations report
  23. GRB 211211A: Enhanced Swift-XRT position
  24. GRB 211207A: Swift/UVOT Detection
  25. GRB 211211A: KAIT Optical Afterglow Candidate
  26. GRB 211211A: Swift detection of a bright burst
  27. GRB 211211A: Fermi GBM Final Real-time Localization
  28. Fermi trigger No 660868196: Global MASTER-Net observations report
  29. IceCube-211208A: No significant detection in HAWC
  30. AMON NuEm-211020A: No neutrino counterpart detected with ANTARES
  31. Fermi trigger No 660736561: Global MASTER-Net observations report
  32. GRB 211130A: MeerLICHT identification of possible afterglow candidate
  33. IceCube-211208A: Upper limits from a search for additional neutrino events in IceCube
  34. Fermi-LAT Gamma-ray Observations of IceCube-211208A
  35. IceCube-211208A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  36. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-211209A
  37. IceCube-211208A - IceCube observation of a high-energy neutrino candidate track-like event
  38. IceCube Alert 211208.84: Global MASTER-Net observations report
  39. GRB 211207A: Swift-BAT refined analysis
  40. GRB 211207A: VLT/X-shooter redshift
  41. Chandra observation of GW170817 at ~1573 days since merger (Epoch 1 of 4)
  42. GRB 211204C: Fermi GBM detection
  43. GRB 211207A: Swift-XRT refined Analysis
  44. GRB 211207A: Enhanced Swift-XRT position
  45. Swift GRB 211207A: Global MASTER-Net observations report
  46. GRB 211207A: Swift detection of a burst with an optical counterpart
  47. GRB 211206A: Not observable by Fermi-GBM
  48. GRB 211206A: AstroSat CZTI detection
  49. GRB 211206B: AstroSat CZTI detection
  50. GRB 211204C: AstroSat CZTI detection
  51. IPN triangulation of GRB 211204C
  52. GRB 211206A: Swift/BAT-GUANO detection outside the coded FOV
  53. GRB 211206A: AGILE/MCAL detection of a burst
  54. GRB 211204C: Swift/BAT-GUANO detection outside the coded FOV
  55. GRB 211204C: GECAM detection
  56. Fermi GRB 211204C: Global MASTER-Net observations report
  57. GRB 211204C: Fermi GBM Final Real-time Localization
  58. Fermi GRB 211204B: Global MASTER-Net observations report
  59. GRB 211204B: Fermi GBM Final Real-time Localization
  60. Fermi GRB 211204A: Global MASTER-Net observations report
  61. GRB 211204A: Fermi GBM Final Real-time Localization
  62. GRB 211124A: Fermi GBM Observation
  63. Swift Trigger 1086826 (possible GRB 211203A) is likely not an astrophysical event
  64. Swift GRB 211203A: Global MASTER-Net observations report
  65. Fermi GBM Upper limits for GRB 211203A
  66. Konus-Wind detection of GRB 211130A
  67. IPN triangulation of GRB 211130A
  68. GRB 211203A: Swift detection of a burst
  69. GRB 211201A: GECAM detection
  70. GRB 211201A: Swift/BAT-GUANO detection likely outside the coded FOV
  71. GRB 211106A: Second HST Observation
  72. Fermi GRB 211201A: Global MASTER-Net observations report
  73. GRB 211201A: Fermi GBM Final Real-time Localization
  74. Fermi GRB 211130A: Global MASTER-Net observations report
  75. IceCube-211125A: No significant detection in HAWC
  76. GRB 211130A: BALROG localization (Fermi Trigger 659978192 / GRB 211130636)
  77. GRB 211130A: Fermi GBM Final Real-time Localization
  78. GRB 211106A: GECAM detection
  79. GRB 211129A: Swift-BAT refined analysis
  80. GRB 211129A: Swift-XRT refined Analysis
  81. GRB 211129A: Swift/UVOT Upper Limits
  82. GRB 211106A: HST Observations
  83. GRB 211106A: Chandra Observations
  84. IceCube-Cascade 211128A: Upper limits from a search for additional neutrino events in IceCube
  85. IceCube-211125A: Upper limits from a search for additional neutrino events in IceCube
  86. GRB 211129A: Fermi GBM observation
  87. Swift GRB 211129A: Global MASTER-Net observations report
  88. GRB 211129A: Nanshan/NEXT optical upper limit
  89. GRB 211129A: Enhanced Swift-XRT position
  90. IPN triangulation of GRB 211118A
  91. GRB 211129A: MITSuME Akeno optical upper limits
  92. GRB 211129A: Swift detection of a burst
  93. IceCube-211125A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  94. GRB 211023A: Xinglong 2.16m optical observations
  95. GRB 211023A: Xinglong 2.16m optical observations
  96. Fermi-LAT Gamma-ray Observations of IceCube-211125A
  97. GRB 211120548: Fermi GBM observation
  98. Konus-Wind detection of GRB 211120A
  99. IPN triangulation of GRB 211120A
  100. IceCube-211125A: No neutrino counterpart detected with ANTARES

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