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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 211219B: AstroSat CZTI detection
  2. GRB 211219A: AstroSat CZTI detection
  3. Fermi GRB 211222A: Global MASTER-Net observations report
  4. GRB 211221A: Swift-XRT refined Analysis
  5. GRB 211222A: Fermi GBM Final Real-time Localization
  6. GRB 211221A: BOOTES-4/MET optical upper limit
  7. GRB 211218A: MITSuME Akeno optical upper limits
  8. GRB 211221A: MeerLICHT optical limits
  9. GRB 211221A: NOT optical limits
  10. GRB 211221A: Enhanced Swift-XRT position
  11. Swift GRB 211221A: Global MASTER-Net observations report
  12. GRB 211221A: Swift detection of a burst
  13. IceCube-211216B: No significant detection in HAWC
  14. IceCube-211216A: No significant detection in HAWC
  15. GRB 211219A: AGILE detection
  16. GRB 211219A: Swift/BAT-GUANO detection outside the coded FOV
  17. Fermi GRB 211219B: Global MASTER-Net observations report
  18. GRB 211219B: Fermi GBM Final Real-time Localization
  19. Fermi GRB 211219A: Global MASTER-Net observations report
  20. GRB 211219A: Fermi GBM Final Real-time Localization
  21. GRB 211211A: MMT/MMIRS Observations Indicate Fading of K-band Source
  22. GRB 211216A: Fermi GBM observation
  23. IceCube-211216B: No neutrino counterpart candidates in ANTARES search
  24. GRB 211218A, MAXI J0909-041: MAXI/GSC detection
  25. MAXI GRB211218.04: Global MASTER-Net observations report
  26. GRB 211106A: XMM-Newton monitoring campaign detections
  27. Fermi-LAT Gamma-ray Observations of IceCube-211216B
  28. Fermi-LAT Gamma-ray Observations of IceCube-211216A
  29. IceCube-211216B: Upper limits from Fermi-GBM Observations
  30. IceCube-211216A: Upper limits from Fermi-GBM Observations
  31. IceCube-211216A: Upper limits from a search for additional neutrino events in IceCube
  32. Fermi trigger No 661417475: Global MASTER-Net observations report
  33. IceCube-211216A: No neutrino counterpart candidates in ANTARES search
  34. GRB 211217A: GECAM detection
  35. GRB 211216A: Swift/BAT-GUANO detection outside the coded FOV
  36. IceCube-211216B - IceCube observation of a high-energy neutrino candidate track-like event
  37. IceCube Alert 211216.99: Global MASTER-Net observations report
  38. Fermi GRB 211216B: Global MASTER-Net observations report
  39. GRB 211216B: GECAM detection
  40. IceCube Alert 211216.30: Global MASTER-Net observations report
  41. GRB 211216B: Fermi GBM Final Real-time Localization
  42. IceCube-211216A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  43. GRB 211211A: TNG NIR observations
  44. IceCube-211216A - IceCube observation of a high-energy neutrino candidate track-like event
  45. GRB 211216A: GECAM detection
  46. GRB 211216A: BALROG localization (Fermi Trigger 661329957 / GRB 211216282)
  47. Fermi GRB 211216A: Global MASTER-Net observations report
  48. GRB 211216A: Fermi GBM Final Real-time Localization
  49. GRB 211211A: Insight-HXMT/HE detection
  50. GRB 211211A - Gemini K-band detection
  51. GRB 211211A: SAO RAS optical observations
  52. GRB 211211A: AbAO optical observations
  53. GRB 211211A: GMG upper limit
  54. Chandra observation of GW170817 at ~1575 days since merger (all epochs)
  55. GRB 211211A: redshift estimation and SPI-ACS/INTEGRAL detection
  56. GRB 211211A: Very fast decay observed from CAFOS/2.2mCAHA
  57. GRB 211211A: Further observations from CAFOS/2.2m CAHA
  58. GRB 211211A: HCT and GIT optical follow up observations
  59. GRB 211211A: CALET Gamma-Ray Burst Monitor detection
  60. IceCube-211208A: No neutrino counterpart detected with ANTARES
  61. Fermi GRB 211212A: Global MASTER-Net observations report
  62. GRB 211211A: incorrect E_iso value in GCN 31221
  63. GRB 211211A: Swift/UVOT detection
  64. GRB 211211A: NOT optical spectroscopy
  65. GRB 211211B: GECAM detection
  66. Fermi GRB 211212B: Global MASTER-Net observations report
  67. GRB 211211A: Afterglow detection from CAFOS/2.2m CAHA
  68. GRB 211211A: MITSuME Akeno optical observation
  69. Swift GRB 211211A: Global MASTER-Net observations report
  70. GRB 211212B: Fermi GBM Final Real-time Localization
  71. GRB 211211A: LCO Optical Observations
  72. GRB 211211A: Nanshan/NEXT optical observations
  73. GRB 211211A: Swift-XRT refined Analysis
  74. GRB 211212A: Fermi GBM Final Real-time Localization
  75. GRB 211211A: Fermi GBM observation
  76. GRB 211211A: Swift-BAT refined analysis
  77. Fermi GRB 211211B: Global MASTER-Net observations report
  78. GRB 211211B: Fermi GBM Final Real-time Localization
  79. Fermi GRB 211211A: Global MASTER-Net observations report
  80. GRB 211211A: Enhanced Swift-XRT position
  81. GRB 211207A: Swift/UVOT Detection
  82. GRB 211211A: KAIT Optical Afterglow Candidate
  83. GRB 211211A: Swift detection of a bright burst
  84. GRB 211211A: Fermi GBM Final Real-time Localization
  85. Fermi trigger No 660868196: Global MASTER-Net observations report
  86. IceCube-211208A: No significant detection in HAWC
  87. AMON NuEm-211020A: No neutrino counterpart detected with ANTARES
  88. Fermi trigger No 660736561: Global MASTER-Net observations report
  89. GRB 211130A: MeerLICHT identification of possible afterglow candidate
  90. IceCube-211208A: Upper limits from a search for additional neutrino events in IceCube
  91. Fermi-LAT Gamma-ray Observations of IceCube-211208A
  92. IceCube-211208A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  93. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-211209A
  94. IceCube-211208A - IceCube observation of a high-energy neutrino candidate track-like event
  95. IceCube Alert 211208.84: Global MASTER-Net observations report
  96. GRB 211207A: Swift-BAT refined analysis
  97. GRB 211207A: VLT/X-shooter redshift
  98. Chandra observation of GW170817 at ~1573 days since merger (Epoch 1 of 4)
  99. GRB 211204C: Fermi GBM detection
  100. GRB 211207A: Swift-XRT refined Analysis

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