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

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