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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 211225B: Swift detection of a burst
  2. MAXI GRB211225.14: Global MASTER-Net observations report
  3. GRB 211225A/MAXI J0827-071: MAXI/GSC detection
  4. Fermi trigger No 662084433: Global MASTER-Net observations report
  5. GRB 211224A: Fermi GBM Final Real-time Localization
  6. GRB 211106A: Third HST Observation
  7. GRB 211211A: observations with the 3.6m Devasthal Optical Telescope
  8. Fermi trigger No 662010159: Global MASTER-Net observations report
  9. GRB 211223C: Swift-BAT refined analysis
  10. AGILE observations of a bright burst from SGR 1935+2154
  11. GRB 211223C: BOOTES-4/MET optical upper limit
  12. Swift GRB 211223C: Global MASTER-Net observations report
  13. GRB 211223A: Insight-HXMT/HE detection
  14. Fermi GRB 211223B: Global MASTER-Net observations report
  15. Fermi GBM Sub-Threshold Detection of GRB 211221A
  16. Fermi GBM Sub-Threshold Detection of GRB 211207A
  17. GRB 211221A: Swift-BAT refined analysis
  18. GRB 211223C: Swift detection of a burst
  19. GRB 211223B: Fermi GBM Final Real-time Localization
  20. GRB 211223A: GECAM detection
  21. GRB 211221A: NUTTelA-TAO / BSTI Early Optical Limits (Preliminary)
  22. GRB 211219B: AstroSat CZTI detection
  23. GRB 211219A: AstroSat CZTI detection
  24. Fermi GRB 211222A: Global MASTER-Net observations report
  25. GRB 211221A: Swift-XRT refined Analysis
  26. GRB 211222A: Fermi GBM Final Real-time Localization
  27. GRB 211221A: BOOTES-4/MET optical upper limit
  28. GRB 211218A: MITSuME Akeno optical upper limits
  29. GRB 211221A: MeerLICHT optical limits
  30. GRB 211221A: NOT optical limits
  31. GRB 211221A: Enhanced Swift-XRT position
  32. Swift GRB 211221A: Global MASTER-Net observations report
  33. GRB 211221A: Swift detection of a burst
  34. IceCube-211216B: No significant detection in HAWC
  35. IceCube-211216A: No significant detection in HAWC
  36. GRB 211219A: AGILE detection
  37. GRB 211219A: Swift/BAT-GUANO detection outside the coded FOV
  38. Fermi GRB 211219B: Global MASTER-Net observations report
  39. GRB 211219B: Fermi GBM Final Real-time Localization
  40. Fermi GRB 211219A: Global MASTER-Net observations report
  41. GRB 211219A: Fermi GBM Final Real-time Localization
  42. GRB 211211A: MMT/MMIRS Observations Indicate Fading of K-band Source
  43. GRB 211216A: Fermi GBM observation
  44. IceCube-211216B: No neutrino counterpart candidates in ANTARES search
  45. GRB 211218A, MAXI J0909-041: MAXI/GSC detection
  46. MAXI GRB211218.04: Global MASTER-Net observations report
  47. GRB 211106A: XMM-Newton monitoring campaign detections
  48. Fermi-LAT Gamma-ray Observations of IceCube-211216B
  49. Fermi-LAT Gamma-ray Observations of IceCube-211216A
  50. IceCube-211216B: Upper limits from Fermi-GBM Observations
  51. IceCube-211216A: Upper limits from Fermi-GBM Observations
  52. IceCube-211216A: Upper limits from a search for additional neutrino events in IceCube
  53. Fermi trigger No 661417475: Global MASTER-Net observations report
  54. IceCube-211216A: No neutrino counterpart candidates in ANTARES search
  55. GRB 211217A: GECAM detection
  56. GRB 211216A: Swift/BAT-GUANO detection outside the coded FOV
  57. IceCube-211216B - IceCube observation of a high-energy neutrino candidate track-like event
  58. IceCube Alert 211216.99: Global MASTER-Net observations report
  59. Fermi GRB 211216B: Global MASTER-Net observations report
  60. GRB 211216B: GECAM detection
  61. IceCube Alert 211216.30: Global MASTER-Net observations report
  62. GRB 211216B: Fermi GBM Final Real-time Localization
  63. IceCube-211216A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  64. GRB 211211A: TNG NIR observations
  65. IceCube-211216A - IceCube observation of a high-energy neutrino candidate track-like event
  66. GRB 211216A: GECAM detection
  67. GRB 211216A: BALROG localization (Fermi Trigger 661329957 / GRB 211216282)
  68. Fermi GRB 211216A: Global MASTER-Net observations report
  69. GRB 211216A: Fermi GBM Final Real-time Localization
  70. GRB 211211A: Insight-HXMT/HE detection
  71. GRB 211211A - Gemini K-band detection
  72. GRB 211211A: SAO RAS optical observations
  73. GRB 211211A: AbAO optical observations
  74. GRB 211211A: GMG upper limit
  75. Chandra observation of GW170817 at ~1575 days since merger (all epochs)
  76. GRB 211211A: redshift estimation and SPI-ACS/INTEGRAL detection
  77. GRB 211211A: Very fast decay observed from CAFOS/2.2mCAHA
  78. GRB 211211A: Further observations from CAFOS/2.2m CAHA
  79. GRB 211211A: HCT and GIT optical follow up observations
  80. GRB 211211A: CALET Gamma-Ray Burst Monitor detection
  81. IceCube-211208A: No neutrino counterpart detected with ANTARES
  82. Fermi GRB 211212A: Global MASTER-Net observations report
  83. GRB 211211A: incorrect E_iso value in GCN 31221
  84. GRB 211211A: Swift/UVOT detection
  85. GRB 211211A: NOT optical spectroscopy
  86. GRB 211211B: GECAM detection
  87. Fermi GRB 211212B: Global MASTER-Net observations report
  88. GRB 211211A: Afterglow detection from CAFOS/2.2m CAHA
  89. GRB 211211A: MITSuME Akeno optical observation
  90. Swift GRB 211211A: Global MASTER-Net observations report
  91. GRB 211212B: Fermi GBM Final Real-time Localization
  92. GRB 211211A: LCO Optical Observations
  93. GRB 211211A: Nanshan/NEXT optical observations
  94. GRB 211211A: Swift-XRT refined Analysis
  95. GRB 211212A: Fermi GBM Final Real-time Localization
  96. GRB 211211A: Fermi GBM observation
  97. GRB 211211A: Swift-BAT refined analysis
  98. Fermi GRB 211211B: Global MASTER-Net observations report
  99. GRB 211211B: Fermi GBM Final Real-time Localization
  100. Fermi GRB 211211A: Global MASTER-Net observations report

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