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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 211225A: MITSuME Akeno optical upper limits
  2. GRB 211226A: AGILE/MCAL detection of a burst
  3. Swift GRB 211225B: Global MASTER-Net observations report
  4. Fermi GRB 211225C: Global MASTER-Net observations report
  5. GRB 211225C: Fermi GBM Final Real-time Localization
  6. GRB 211225B: Swift detection of a burst
  7. MAXI GRB211225.14: Global MASTER-Net observations report
  8. GRB 211225A/MAXI J0827-071: MAXI/GSC detection
  9. Fermi trigger No 662084433: Global MASTER-Net observations report
  10. GRB 211224A: Fermi GBM Final Real-time Localization
  11. GRB 211106A: Third HST Observation
  12. GRB 211211A: observations with the 3.6m Devasthal Optical Telescope
  13. Fermi trigger No 662010159: Global MASTER-Net observations report
  14. GRB 211223C: Swift-BAT refined analysis
  15. AGILE observations of a bright burst from SGR 1935+2154
  16. GRB 211223C: BOOTES-4/MET optical upper limit
  17. Swift GRB 211223C: Global MASTER-Net observations report
  18. GRB 211223A: Insight-HXMT/HE detection
  19. Fermi GRB 211223B: Global MASTER-Net observations report
  20. Fermi GBM Sub-Threshold Detection of GRB 211221A
  21. Fermi GBM Sub-Threshold Detection of GRB 211207A
  22. GRB 211221A: Swift-BAT refined analysis
  23. GRB 211223C: Swift detection of a burst
  24. GRB 211223B: Fermi GBM Final Real-time Localization
  25. GRB 211223A: GECAM detection
  26. GRB 211221A: NUTTelA-TAO / BSTI Early Optical Limits (Preliminary)
  27. GRB 211219B: AstroSat CZTI detection
  28. GRB 211219A: AstroSat CZTI detection
  29. Fermi GRB 211222A: Global MASTER-Net observations report
  30. GRB 211221A: Swift-XRT refined Analysis
  31. GRB 211222A: Fermi GBM Final Real-time Localization
  32. GRB 211221A: BOOTES-4/MET optical upper limit
  33. GRB 211218A: MITSuME Akeno optical upper limits
  34. GRB 211221A: MeerLICHT optical limits
  35. GRB 211221A: NOT optical limits
  36. GRB 211221A: Enhanced Swift-XRT position
  37. Swift GRB 211221A: Global MASTER-Net observations report
  38. GRB 211221A: Swift detection of a burst
  39. IceCube-211216B: No significant detection in HAWC
  40. IceCube-211216A: No significant detection in HAWC
  41. GRB 211219A: AGILE detection
  42. GRB 211219A: Swift/BAT-GUANO detection outside the coded FOV
  43. Fermi GRB 211219B: Global MASTER-Net observations report
  44. GRB 211219B: Fermi GBM Final Real-time Localization
  45. Fermi GRB 211219A: Global MASTER-Net observations report
  46. GRB 211219A: Fermi GBM Final Real-time Localization
  47. GRB 211211A: MMT/MMIRS Observations Indicate Fading of K-band Source
  48. GRB 211216A: Fermi GBM observation
  49. IceCube-211216B: No neutrino counterpart candidates in ANTARES search
  50. GRB 211218A, MAXI J0909-041: MAXI/GSC detection
  51. MAXI GRB211218.04: Global MASTER-Net observations report
  52. GRB 211106A: XMM-Newton monitoring campaign detections
  53. Fermi-LAT Gamma-ray Observations of IceCube-211216B
  54. Fermi-LAT Gamma-ray Observations of IceCube-211216A
  55. IceCube-211216B: Upper limits from Fermi-GBM Observations
  56. IceCube-211216A: Upper limits from Fermi-GBM Observations
  57. IceCube-211216A: Upper limits from a search for additional neutrino events in IceCube
  58. Fermi trigger No 661417475: Global MASTER-Net observations report
  59. IceCube-211216A: No neutrino counterpart candidates in ANTARES search
  60. GRB 211217A: GECAM detection
  61. GRB 211216A: Swift/BAT-GUANO detection outside the coded FOV
  62. IceCube-211216B - IceCube observation of a high-energy neutrino candidate track-like event
  63. IceCube Alert 211216.99: Global MASTER-Net observations report
  64. Fermi GRB 211216B: Global MASTER-Net observations report
  65. GRB 211216B: GECAM detection
  66. IceCube Alert 211216.30: Global MASTER-Net observations report
  67. GRB 211216B: Fermi GBM Final Real-time Localization
  68. IceCube-211216A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  69. GRB 211211A: TNG NIR observations
  70. IceCube-211216A - IceCube observation of a high-energy neutrino candidate track-like event
  71. GRB 211216A: GECAM detection
  72. GRB 211216A: BALROG localization (Fermi Trigger 661329957 / GRB 211216282)
  73. Fermi GRB 211216A: Global MASTER-Net observations report
  74. GRB 211216A: Fermi GBM Final Real-time Localization
  75. GRB 211211A: Insight-HXMT/HE detection
  76. GRB 211211A - Gemini K-band detection
  77. GRB 211211A: SAO RAS optical observations
  78. GRB 211211A: AbAO optical observations
  79. GRB 211211A: GMG upper limit
  80. Chandra observation of GW170817 at ~1575 days since merger (all epochs)
  81. GRB 211211A: redshift estimation and SPI-ACS/INTEGRAL detection
  82. GRB 211211A: Very fast decay observed from CAFOS/2.2mCAHA
  83. GRB 211211A: Further observations from CAFOS/2.2m CAHA
  84. GRB 211211A: HCT and GIT optical follow up observations
  85. GRB 211211A: CALET Gamma-Ray Burst Monitor detection
  86. IceCube-211208A: No neutrino counterpart detected with ANTARES
  87. Fermi GRB 211212A: Global MASTER-Net observations report
  88. GRB 211211A: incorrect E_iso value in GCN 31221
  89. GRB 211211A: Swift/UVOT detection
  90. GRB 211211A: NOT optical spectroscopy
  91. GRB 211211B: GECAM detection
  92. Fermi GRB 211212B: Global MASTER-Net observations report
  93. GRB 211211A: Afterglow detection from CAFOS/2.2m CAHA
  94. GRB 211211A: MITSuME Akeno optical observation
  95. Swift GRB 211211A: Global MASTER-Net observations report
  96. GRB 211212B: Fermi GBM Final Real-time Localization
  97. GRB 211211A: LCO Optical Observations
  98. GRB 211211A: Nanshan/NEXT optical observations
  99. GRB 211211A: Swift-XRT refined Analysis
  100. GRB 211212A: Fermi GBM Final Real-time Localization

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