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

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