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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 200924A: Fermi GBM Final Real-time Localization
  2. Fermi GRB 200923A: Global MASTER-Net observations report
  3. IceCube Alert 200921.80: Global MASTER-Net observations report
  4. GRB 200923A: Fermi GBM Final Real-time Localization
  5. IceCube-200921A: Upper limits from a search for additional neutrino events in IceCube
  6. GRB 200922A: Swift-BAT refined analysis
  7. Improved enhanced Swift-XRT position of GRB 200922A
  8. GRB 200922A: Swift/UVOT Detection
  9. Fermi-LAT Gamma-ray Observations of IceCube-200921A and detection of a new gamma-ray source, Fermi J1256.9+2630
  10. IceCube-200921A: no significant detection in HAWC observations
  11. Fermi GRB 200922B: Global MASTER-Net observations report
  12. GRB 200922A: LCO observations
  13. Swift GRB 200922A: Global MASTER-Net observations report
  14. GRB 200922A: Swift-XRT refined Analysis
  15. GRB 200917A: Swift/UVOT Upper Limits
  16. GRB 200922B: Fermi GBM Final Real-time Localization
  17. GRB 200922A: Enhanced Swift-XRT position
  18. GRB 200919C: Insight-HXMT/HE detection
  19. GRB 200922A: Swift detection of a burst with possible optical counterpart
  20. IceCube-200921A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  21. IceCube-200921A: Upper limits from Fermi-GBM Observations
  22. IceCube-200921A: IceCube observation of a high-energy neutrino candidate event
  23. IPN triangulation of GRB 200920B (short)
  24. GRB 200914A: Swift-XRT further observations
  25. IceCube-200916A - ZTF20acaapwk/SN2020tno classified as SN Ia
  26. GRB 200920B: AGILE/MCAL detection of a burst
  27. GRB 200920A: Fermi GBM Final Real-time Localization
  28. Fermi GRB 200919C: Global MASTER-Net observations report
  29. GRB 200919C: Fermi GBM Final Real-time Localization
  30. GRB 200919A: CrAO/ZTSh early optical upper limit
  31. Fermi GRB 200919B: Global MASTER-Net observations report
  32. GRB 200919A: Swift-BAT refined analysis
  33. GRB 200919B: Fermi GBM Final Real-time Localization
  34. GRB 200916B: MASTER optical observation
  35. Swift GRB200919.08: Global MASTER-Net observations report
  36. GRB 200919A: Swift detection of a burst
  37. IceCube-200916A: AbAO observations of optical candidates ZTF20acaapwk/AT2020tno, ZTF20acaapwo/AT2020tnp
  38. IceCube-200916A: Upper limits from a search for additional neutrino events in IceCube
  39. GRB 200916B: AstroSat CZTI detection
  40. GRB 200917A: GROWTH-India Telescope optical upper limit.
  41. Swift-XRT observations of IceCube 200916A
  42. IceCube-200916A: No significant detection in HAWC
  43. GRB 200917A: Swift-BAT refined analysis
  44. IceCube-200916A: No neutrino counterpart candidates in ANTARES search
  45. Fermi-GBM Sub-Threshold Detection of GRB 200917A
  46. GRB 200917A: Swift-XRT refined Analysis
  47. IceCube-200916A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  48. Swift GRB 200917A: Global MASTER-Net observations report
  49. IceCube-200916A: Two Candidate Counterparts from the Zwicky Transient Facility
  50. IPN triangulation of GRB 200916B (short)
  51. IceCube-200916A: Upper limits from Fermi-GBM Observations
  52. Fermi-LAT Gamma-ray Observations of IceCube-200916A
  53. IceCube Alert 200916.86: Global MASTER-Net observations report
  54. GRB 200917A: Enhanced Swift-XRT position
  55. GRB 200917A: Swift detection of a burst
  56. Swift-XRT observations of IceCube 200911A
  57. IceCube-200916A - IceCube observation of a high-energy neutrino candidate track-like event
  58. Fermi GRB 200916A: Global MASTER-Net observations report
  59. GRB 200916A: Fermi GBM Final Real-time Localization
  60. Fermi trigger No 621893860: Global MASTER-Net observations report
  61. Fermi trigger No 621833240: Global MASTER-Net observations report
  62. Integral GRB200914.53: Global MASTER-Net observations report
  63. Fermi GRB 200914A: Global MASTER-Net observations report
  64. GRB 200914A: AGILE detection
  65. GRB 200914A: Swift-XRT observations
  66. GRB 200914A: Fermi GBM observation
  67. IceCube Alert 200914.00: Global MASTER-Net observations report
  68. IceCube-200911A: No significant detection in HAWC
  69. Fermi-LAT Gamma-ray Observations of IceCube-200911A and detection of a new gamma-ray source, Fermi J0330.1+3743
  70. GRB 200914A: Swift ToO observations
  71. GRB 200914A : A long GRB detected by INTEGRAL
  72. GRB 200914A: BALROG localization (Fermi Trigger 621780515 / GRB 200914534)
  73. GRB 200914A: Fermi GBM Final Real-time Localization
  74. IceCube-200911A: Upper limits from a search for additional neutrino events in IceCube
  75. IceCube-200911A: No neutrino counterpart candidates in ANTARES search
  76. IceCube Alert 200911.60: Global MASTER-Net observations report
  77. IceCube-200911A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  78. IceCube-200911A: not observable by Fermi-GBM
  79. IceCube-200911A: IceCube observation of a high-energy neutrino candidate event
  80. GRB 200826A: uGMRT radio upper limit at 1.25 GHz
  81. IPN triangulation of GRB 200907A (short)
  82. GRB 200909B: Swift-BAT refined analysis
  83. Swift GRB200909.97: Global MASTER-Net observations report
  84. GRB 200909B: Swift detection of a burst
  85. GRB 200909A: AstroSat CZTI detection
  86. GRB 200829A: T100 observations
  87. Fermi GRB 200909A: Global MASTER-Net observations report
  88. GRB 200909A: BALROG localization (Fermi Trigger 621316887 / GRB 200909168)
  89. GRB 200909A: Fermi GBM Final Real-time Localization
  90. GRB 200907B: Swift/UVOT Upper Limits
  91. Fermi GRB 200908A: Global MASTER-Net observations report
  92. GRB 200907B: Swift-BAT refined analysis
  93. Konus-Wind detection of GRB 200903E
  94. GRB 200908A: Fermi GBM Final Real-time Localization
  95. GRB 200907B: AstroSat CZTI detection
  96. GRB 200907B: Swift-XRT refined Analysis
  97. GRB 200907B: MITSuME Okayama optical upper limits
  98. Swift GRB 200907B: Global MASTER-Net observations report
  99. GRB 200907B: Enhanced Swift-XRT position
  100. Fermi GRB 200907C: Global MASTER-Net observations report

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