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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 200922A: Chilescope optical observations
  2. IceCube-200926A: IceCube observation of a high-energy neutrino candidate event
  3. GRB 200925B: Enhanced Swift-XRT position
  4. Swift GRB 200925B: Global MASTER-Net OT detection
  5. GRB 200925B: OSN Afterglow Candidate Discovery
  6. GRB 200925B: Prompt enhanced Swift-XRT position
  7. GRB 200925B: Swift detection of a burst
  8. Swift GRB200925.91: Global MASTER-Net observations report
  9. Fermi GRB 200925A: Global MASTER-Net observations report
  10. GRB 200925A: Fermi GBM Final Real-time Localization
  11. Konus-Wind observation of GRB 200914A
  12. Fermi GRB 200924A: Global MASTER-Net observations report
  13. GRB 200924B: Fermi GBM Final Localization
  14. GRB 200922A: chance superposition between optical afterglow and archival star
  15. Fermi trigger No 622618714: Global MASTER-Net observations report
  16. GRB 200922A: Insight-HXMT/HE detection
  17. GRB 200924A: Fermi GBM Final Real-time Localization
  18. Fermi GRB 200923A: Global MASTER-Net observations report
  19. IceCube Alert 200921.80: Global MASTER-Net observations report
  20. GRB 200923A: Fermi GBM Final Real-time Localization
  21. IceCube-200921A: Upper limits from a search for additional neutrino events in IceCube
  22. GRB 200922A: Swift-BAT refined analysis
  23. Improved enhanced Swift-XRT position of GRB 200922A
  24. GRB 200922A: Swift/UVOT Detection
  25. Fermi-LAT Gamma-ray Observations of IceCube-200921A and detection of a new gamma-ray source, Fermi J1256.9+2630
  26. IceCube-200921A: no significant detection in HAWC observations
  27. Fermi GRB 200922B: Global MASTER-Net observations report
  28. GRB 200922A: LCO observations
  29. Swift GRB 200922A: Global MASTER-Net observations report
  30. GRB 200922A: Swift-XRT refined Analysis
  31. GRB 200917A: Swift/UVOT Upper Limits
  32. GRB 200922B: Fermi GBM Final Real-time Localization
  33. GRB 200922A: Enhanced Swift-XRT position
  34. GRB 200919C: Insight-HXMT/HE detection
  35. GRB 200922A: Swift detection of a burst with possible optical counterpart
  36. IceCube-200921A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  37. IceCube-200921A: Upper limits from Fermi-GBM Observations
  38. IceCube-200921A: IceCube observation of a high-energy neutrino candidate event
  39. IPN triangulation of GRB 200920B (short)
  40. GRB 200914A: Swift-XRT further observations
  41. IceCube-200916A - ZTF20acaapwk/SN2020tno classified as SN Ia
  42. GRB 200920B: AGILE/MCAL detection of a burst
  43. GRB 200920A: Fermi GBM Final Real-time Localization
  44. Fermi GRB 200919C: Global MASTER-Net observations report
  45. GRB 200919C: Fermi GBM Final Real-time Localization
  46. GRB 200919A: CrAO/ZTSh early optical upper limit
  47. Fermi GRB 200919B: Global MASTER-Net observations report
  48. GRB 200919A: Swift-BAT refined analysis
  49. GRB 200919B: Fermi GBM Final Real-time Localization
  50. GRB 200916B: MASTER optical observation
  51. Swift GRB200919.08: Global MASTER-Net observations report
  52. GRB 200919A: Swift detection of a burst
  53. IceCube-200916A: AbAO observations of optical candidates ZTF20acaapwk/AT2020tno, ZTF20acaapwo/AT2020tnp
  54. IceCube-200916A: Upper limits from a search for additional neutrino events in IceCube
  55. GRB 200916B: AstroSat CZTI detection
  56. GRB 200917A: GROWTH-India Telescope optical upper limit.
  57. Swift-XRT observations of IceCube 200916A
  58. IceCube-200916A: No significant detection in HAWC
  59. GRB 200917A: Swift-BAT refined analysis
  60. IceCube-200916A: No neutrino counterpart candidates in ANTARES search
  61. Fermi-GBM Sub-Threshold Detection of GRB 200917A
  62. GRB 200917A: Swift-XRT refined Analysis
  63. IceCube-200916A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  64. Swift GRB 200917A: Global MASTER-Net observations report
  65. IceCube-200916A: Two Candidate Counterparts from the Zwicky Transient Facility
  66. IPN triangulation of GRB 200916B (short)
  67. IceCube-200916A: Upper limits from Fermi-GBM Observations
  68. Fermi-LAT Gamma-ray Observations of IceCube-200916A
  69. IceCube Alert 200916.86: Global MASTER-Net observations report
  70. GRB 200917A: Enhanced Swift-XRT position
  71. GRB 200917A: Swift detection of a burst
  72. Swift-XRT observations of IceCube 200911A
  73. IceCube-200916A - IceCube observation of a high-energy neutrino candidate track-like event
  74. Fermi GRB 200916A: Global MASTER-Net observations report
  75. GRB 200916A: Fermi GBM Final Real-time Localization
  76. Fermi trigger No 621893860: Global MASTER-Net observations report
  77. Fermi trigger No 621833240: Global MASTER-Net observations report
  78. Integral GRB200914.53: Global MASTER-Net observations report
  79. Fermi GRB 200914A: Global MASTER-Net observations report
  80. GRB 200914A: AGILE detection
  81. GRB 200914A: Swift-XRT observations
  82. GRB 200914A: Fermi GBM observation
  83. IceCube Alert 200914.00: Global MASTER-Net observations report
  84. IceCube-200911A: No significant detection in HAWC
  85. Fermi-LAT Gamma-ray Observations of IceCube-200911A and detection of a new gamma-ray source, Fermi J0330.1+3743
  86. GRB 200914A: Swift ToO observations
  87. GRB 200914A : A long GRB detected by INTEGRAL
  88. GRB 200914A: BALROG localization (Fermi Trigger 621780515 / GRB 200914534)
  89. GRB 200914A: Fermi GBM Final Real-time Localization
  90. IceCube-200911A: Upper limits from a search for additional neutrino events in IceCube
  91. IceCube-200911A: No neutrino counterpart candidates in ANTARES search
  92. IceCube Alert 200911.60: Global MASTER-Net observations report
  93. IceCube-200911A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  94. IceCube-200911A: not observable by Fermi-GBM
  95. IceCube-200911A: IceCube observation of a high-energy neutrino candidate event
  96. GRB 200826A: uGMRT radio upper limit at 1.25 GHz
  97. IPN triangulation of GRB 200907A (short)
  98. GRB 200909B: Swift-BAT refined analysis
  99. Swift GRB200909.97: Global MASTER-Net observations report
  100. GRB 200909B: Swift detection of a burst

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