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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. IceCube-211216A: No significant detection in HAWC
  2. GRB 211219A: AGILE detection
  3. GRB 211219A: Swift/BAT-GUANO detection outside the coded FOV
  4. Fermi GRB 211219B: Global MASTER-Net observations report
  5. GRB 211219B: Fermi GBM Final Real-time Localization
  6. Fermi GRB 211219A: Global MASTER-Net observations report
  7. GRB 211219A: Fermi GBM Final Real-time Localization
  8. GRB 211211A: MMT/MMIRS Observations Indicate Fading of K-band Source
  9. GRB 211216A: Fermi GBM observation
  10. IceCube-211216B: No neutrino counterpart candidates in ANTARES search
  11. GRB 211218A, MAXI J0909-041: MAXI/GSC detection
  12. MAXI GRB211218.04: Global MASTER-Net observations report
  13. GRB 211106A: XMM-Newton monitoring campaign detections
  14. Fermi-LAT Gamma-ray Observations of IceCube-211216B
  15. Fermi-LAT Gamma-ray Observations of IceCube-211216A
  16. IceCube-211216B: Upper limits from Fermi-GBM Observations
  17. IceCube-211216A: Upper limits from Fermi-GBM Observations
  18. IceCube-211216A: Upper limits from a search for additional neutrino events in IceCube
  19. Fermi trigger No 661417475: Global MASTER-Net observations report
  20. IceCube-211216A: No neutrino counterpart candidates in ANTARES search
  21. GRB 211217A: GECAM detection
  22. GRB 211216A: Swift/BAT-GUANO detection outside the coded FOV
  23. IceCube-211216B - IceCube observation of a high-energy neutrino candidate track-like event
  24. IceCube Alert 211216.99: Global MASTER-Net observations report
  25. Fermi GRB 211216B: Global MASTER-Net observations report
  26. GRB 211216B: GECAM detection
  27. IceCube Alert 211216.30: Global MASTER-Net observations report
  28. GRB 211216B: Fermi GBM Final Real-time Localization
  29. IceCube-211216A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  30. GRB 211211A: TNG NIR observations
  31. IceCube-211216A - IceCube observation of a high-energy neutrino candidate track-like event
  32. GRB 211216A: GECAM detection
  33. GRB 211216A: BALROG localization (Fermi Trigger 661329957 / GRB 211216282)
  34. Fermi GRB 211216A: Global MASTER-Net observations report
  35. GRB 211216A: Fermi GBM Final Real-time Localization
  36. GRB 211211A: Insight-HXMT/HE detection
  37. GRB 211211A - Gemini K-band detection
  38. GRB 211211A: SAO RAS optical observations
  39. GRB 211211A: AbAO optical observations
  40. GRB 211211A: GMG upper limit
  41. Chandra observation of GW170817 at ~1575 days since merger (all epochs)
  42. GRB 211211A: redshift estimation and SPI-ACS/INTEGRAL detection
  43. GRB 211211A: Very fast decay observed from CAFOS/2.2mCAHA
  44. GRB 211211A: Further observations from CAFOS/2.2m CAHA
  45. GRB 211211A: HCT and GIT optical follow up observations
  46. GRB 211211A: CALET Gamma-Ray Burst Monitor detection
  47. IceCube-211208A: No neutrino counterpart detected with ANTARES
  48. Fermi GRB 211212A: Global MASTER-Net observations report
  49. GRB 211211A: incorrect E_iso value in GCN 31221
  50. GRB 211211A: Swift/UVOT detection
  51. GRB 211211A: NOT optical spectroscopy
  52. GRB 211211B: GECAM detection
  53. Fermi GRB 211212B: Global MASTER-Net observations report
  54. GRB 211211A: Afterglow detection from CAFOS/2.2m CAHA
  55. GRB 211211A: MITSuME Akeno optical observation
  56. Swift GRB 211211A: Global MASTER-Net observations report
  57. GRB 211212B: Fermi GBM Final Real-time Localization
  58. GRB 211211A: LCO Optical Observations
  59. GRB 211211A: Nanshan/NEXT optical observations
  60. GRB 211211A: Swift-XRT refined Analysis
  61. GRB 211212A: Fermi GBM Final Real-time Localization
  62. GRB 211211A: Fermi GBM observation
  63. GRB 211211A: Swift-BAT refined analysis
  64. Fermi GRB 211211B: Global MASTER-Net observations report
  65. GRB 211211B: Fermi GBM Final Real-time Localization
  66. Fermi GRB 211211A: Global MASTER-Net observations report
  67. GRB 211211A: Enhanced Swift-XRT position
  68. GRB 211207A: Swift/UVOT Detection
  69. GRB 211211A: KAIT Optical Afterglow Candidate
  70. GRB 211211A: Swift detection of a bright burst
  71. GRB 211211A: Fermi GBM Final Real-time Localization
  72. Fermi trigger No 660868196: Global MASTER-Net observations report
  73. IceCube-211208A: No significant detection in HAWC
  74. AMON NuEm-211020A: No neutrino counterpart detected with ANTARES
  75. Fermi trigger No 660736561: Global MASTER-Net observations report
  76. GRB 211130A: MeerLICHT identification of possible afterglow candidate
  77. IceCube-211208A: Upper limits from a search for additional neutrino events in IceCube
  78. Fermi-LAT Gamma-ray Observations of IceCube-211208A
  79. IceCube-211208A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  80. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-211209A
  81. IceCube-211208A - IceCube observation of a high-energy neutrino candidate track-like event
  82. IceCube Alert 211208.84: Global MASTER-Net observations report
  83. GRB 211207A: Swift-BAT refined analysis
  84. GRB 211207A: VLT/X-shooter redshift
  85. Chandra observation of GW170817 at ~1573 days since merger (Epoch 1 of 4)
  86. GRB 211204C: Fermi GBM detection
  87. GRB 211207A: Swift-XRT refined Analysis
  88. GRB 211207A: Enhanced Swift-XRT position
  89. Swift GRB 211207A: Global MASTER-Net observations report
  90. GRB 211207A: Swift detection of a burst with an optical counterpart
  91. GRB 211206A: Not observable by Fermi-GBM
  92. GRB 211206A: AstroSat CZTI detection
  93. GRB 211206B: AstroSat CZTI detection
  94. GRB 211204C: AstroSat CZTI detection
  95. IPN triangulation of GRB 211204C
  96. GRB 211206A: Swift/BAT-GUANO detection outside the coded FOV
  97. GRB 211206A: AGILE/MCAL detection of a burst
  98. GRB 211204C: Swift/BAT-GUANO detection outside the coded FOV
  99. GRB 211204C: GECAM detection
  100. Fermi GRB 211204C: Global MASTER-Net observations report

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