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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 211223C: Swift detection of a burst
  2. GRB 211223B: Fermi GBM Final Real-time Localization
  3. GRB 211223A: GECAM detection
  4. GRB 211221A: NUTTelA-TAO / BSTI Early Optical Limits (Preliminary)
  5. GRB 211219B: AstroSat CZTI detection
  6. GRB 211219A: AstroSat CZTI detection
  7. Fermi GRB 211222A: Global MASTER-Net observations report
  8. GRB 211221A: Swift-XRT refined Analysis
  9. GRB 211222A: Fermi GBM Final Real-time Localization
  10. GRB 211221A: BOOTES-4/MET optical upper limit
  11. GRB 211218A: MITSuME Akeno optical upper limits
  12. GRB 211221A: MeerLICHT optical limits
  13. GRB 211221A: NOT optical limits
  14. GRB 211221A: Enhanced Swift-XRT position
  15. Swift GRB 211221A: Global MASTER-Net observations report
  16. GRB 211221A: Swift detection of a burst
  17. IceCube-211216B: No significant detection in HAWC
  18. IceCube-211216A: No significant detection in HAWC
  19. GRB 211219A: AGILE detection
  20. GRB 211219A: Swift/BAT-GUANO detection outside the coded FOV
  21. Fermi GRB 211219B: Global MASTER-Net observations report
  22. GRB 211219B: Fermi GBM Final Real-time Localization
  23. Fermi GRB 211219A: Global MASTER-Net observations report
  24. GRB 211219A: Fermi GBM Final Real-time Localization
  25. GRB 211211A: MMT/MMIRS Observations Indicate Fading of K-band Source
  26. GRB 211216A: Fermi GBM observation
  27. IceCube-211216B: No neutrino counterpart candidates in ANTARES search
  28. GRB 211218A, MAXI J0909-041: MAXI/GSC detection
  29. MAXI GRB211218.04: Global MASTER-Net observations report
  30. GRB 211106A: XMM-Newton monitoring campaign detections
  31. Fermi-LAT Gamma-ray Observations of IceCube-211216B
  32. Fermi-LAT Gamma-ray Observations of IceCube-211216A
  33. IceCube-211216B: Upper limits from Fermi-GBM Observations
  34. IceCube-211216A: Upper limits from Fermi-GBM Observations
  35. IceCube-211216A: Upper limits from a search for additional neutrino events in IceCube
  36. Fermi trigger No 661417475: Global MASTER-Net observations report
  37. IceCube-211216A: No neutrino counterpart candidates in ANTARES search
  38. GRB 211217A: GECAM detection
  39. GRB 211216A: Swift/BAT-GUANO detection outside the coded FOV
  40. IceCube-211216B - IceCube observation of a high-energy neutrino candidate track-like event
  41. IceCube Alert 211216.99: Global MASTER-Net observations report
  42. Fermi GRB 211216B: Global MASTER-Net observations report
  43. GRB 211216B: GECAM detection
  44. IceCube Alert 211216.30: Global MASTER-Net observations report
  45. GRB 211216B: Fermi GBM Final Real-time Localization
  46. IceCube-211216A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  47. GRB 211211A: TNG NIR observations
  48. IceCube-211216A - IceCube observation of a high-energy neutrino candidate track-like event
  49. GRB 211216A: GECAM detection
  50. GRB 211216A: BALROG localization (Fermi Trigger 661329957 / GRB 211216282)
  51. Fermi GRB 211216A: Global MASTER-Net observations report
  52. GRB 211216A: Fermi GBM Final Real-time Localization
  53. GRB 211211A: Insight-HXMT/HE detection
  54. GRB 211211A - Gemini K-band detection
  55. GRB 211211A: SAO RAS optical observations
  56. GRB 211211A: AbAO optical observations
  57. GRB 211211A: GMG upper limit
  58. Chandra observation of GW170817 at ~1575 days since merger (all epochs)
  59. GRB 211211A: redshift estimation and SPI-ACS/INTEGRAL detection
  60. GRB 211211A: Very fast decay observed from CAFOS/2.2mCAHA
  61. GRB 211211A: Further observations from CAFOS/2.2m CAHA
  62. GRB 211211A: HCT and GIT optical follow up observations
  63. GRB 211211A: CALET Gamma-Ray Burst Monitor detection
  64. IceCube-211208A: No neutrino counterpart detected with ANTARES
  65. Fermi GRB 211212A: Global MASTER-Net observations report
  66. GRB 211211A: incorrect E_iso value in GCN 31221
  67. GRB 211211A: Swift/UVOT detection
  68. GRB 211211A: NOT optical spectroscopy
  69. GRB 211211B: GECAM detection
  70. Fermi GRB 211212B: Global MASTER-Net observations report
  71. GRB 211211A: Afterglow detection from CAFOS/2.2m CAHA
  72. GRB 211211A: MITSuME Akeno optical observation
  73. Swift GRB 211211A: Global MASTER-Net observations report
  74. GRB 211212B: Fermi GBM Final Real-time Localization
  75. GRB 211211A: LCO Optical Observations
  76. GRB 211211A: Nanshan/NEXT optical observations
  77. GRB 211211A: Swift-XRT refined Analysis
  78. GRB 211212A: Fermi GBM Final Real-time Localization
  79. GRB 211211A: Fermi GBM observation
  80. GRB 211211A: Swift-BAT refined analysis
  81. Fermi GRB 211211B: Global MASTER-Net observations report
  82. GRB 211211B: Fermi GBM Final Real-time Localization
  83. Fermi GRB 211211A: Global MASTER-Net observations report
  84. GRB 211211A: Enhanced Swift-XRT position
  85. GRB 211207A: Swift/UVOT Detection
  86. GRB 211211A: KAIT Optical Afterglow Candidate
  87. GRB 211211A: Swift detection of a bright burst
  88. GRB 211211A: Fermi GBM Final Real-time Localization
  89. Fermi trigger No 660868196: Global MASTER-Net observations report
  90. IceCube-211208A: No significant detection in HAWC
  91. AMON NuEm-211020A: No neutrino counterpart detected with ANTARES
  92. Fermi trigger No 660736561: Global MASTER-Net observations report
  93. GRB 211130A: MeerLICHT identification of possible afterglow candidate
  94. IceCube-211208A: Upper limits from a search for additional neutrino events in IceCube
  95. Fermi-LAT Gamma-ray Observations of IceCube-211208A
  96. IceCube-211208A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  97. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-211209A
  98. IceCube-211208A - IceCube observation of a high-energy neutrino candidate track-like event
  99. IceCube Alert 211208.84: Global MASTER-Net observations report
  100. GRB 211207A: Swift-BAT refined analysis

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