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

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