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

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