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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 210610A: 1.5m OSN optical observation
  2. GRB 210610B: correction to GCN 30181
  3. HAWC Transient Monitoring Alert: Significant Spot after 3 transits
  4. GRB 210610B: NOT optical observations and tentative redshift
  5. GRB 210610B: iTelescope optical afterglow observations
  6. GRB210610B: MeerLICHT multi-colour photometry
  7. Fermi trigger No 645047470: Global MASTER-Net observations report
  8. GRB 210610B: CrAO/ZTSh optical afterglow photometry
  9. GRB 210610B: BOOTES-2/TELMA optical observation
  10. Swift GRB 210610B: Global MASTER-Net observations report
  11. GRB 210610B: CrAO/ZTSh optical observations
  12. GRB 210610B: GIT optical detection
  13. Swift GRB210610.83: Global MASTER-Net OT detection
  14. GRB 210606A: Swift-XRT afterglow detection
  15. GRB 210610B: BALROG localization (Fermi Trigger 645047470 / GRB 210610827)
  16. GRB 210610B: Swift detection of a burst with bright optical afterglow
  17. GRB 210610A: MITSuME Ishigaki optical observation
  18. GRB210610A: MeerLICHT multi-colour photometry
  19. Swift GRB 210610A: Global MASTER-Net observations report
  20. Swift GRB 210610A: MASTER optical counterpart observation
  21. GRB 210610A: Enhanced Swift-XRT position
  22. GRB 210610A: Xinglong-2.16m redshift
  23. GRB 210610A: GIT optical detection
  24. GRB 210610A: Xinglong-2.16m optical afterglow observations
  25. GRB 210610A: MITSuME Akeno optical observation
  26. GRB 210610A: Swift detection of a burst with an optical counterpart
  27. GRB 210607B: Insight-HXMT/HE detection
  28. GRB 210605A: CALET Gamma-Ray Burst Monitor detection
  29. Konus-Wind detection of GRB 210606B
  30. Fermi-LAT Gamma-ray Observations of IceCube-210608A
  31. IceCube-210608A: not observable by Fermi-GBM
  32. IPN triangulation of GRB 210606B
  33. IceCube-210608A: IceCube observation of a high-energy neutrino candidate track-like event
  34. IceCube Alert 210608.15: Global MASTER-Net observations report
  35. Fermi Gamma-ray Burst Monitor trigger 644793834 / 210607892 is not a GRB
  36. GRB 210607A/MAXI J1733-222: MAXI/GSC detection
  37. MAXI GRB210607.82: Global MASTER-Net observations report
  38. Fermi trigger No 644793834: Global MASTER-Net observations report
  39. GRB 210606B: Fermi GBM detection
  40. GRB 210605B: Swift-XRT observations
  41. Konus-Wind detection of GRB 210602A
  42. Konus-Wind detection of GRB 210605A (short/hard)
  43. IPN triangulation of GRB 210605A (short)
  44. GRB 210606B: AGILE detection
  45. GRB 210606A: 1.5m OSN optical upper limit
  46. GECAM Sub-Threshold Detection of new magnetar Swift SGR J1555.2-5402
  47. GRB 210606B: BALROG localization (Fermi Trigger 644712030 / GRB 210606945)
  48. GRB 210606B: GECAM detection
  49. Fermi trigger No 644712030: Global MASTER-Net observations report
  50. GRB 210606A: Swift ToO observations
  51. Fermi GRB 210606A: DDOTI Upper Limits on the Afterglow
  52. GRB 210606A: Swift/BAT-GUANO detection and arcminute localization
  53. GRB 210605B: Swift ToO observations
  54. Fermi GRB 210606A: Global MASTER-Net observations report
  55. GRB 210606A: Fermi GBM Final Real-time Localization
  56. GRB 210605B: Swift/BAT-GUANO detection and arcminute localization
  57. GRB 210605B: Fermi GBM Final Real-time Localization
  58. Fermi GRB 210605A: Global MASTER-Net observations report
  59. GRB 210605A: Fermi GBM Final Real-time Localization
  60. Initial results of a NICER X-ray monitoring of the magnetar, Swift J1555.2-5402
  61. Fermi GBM Sub-Threshold Detection of new Swift SGR J1555.2-5402
  62. SGR J1555.2-5402: Swift-BAT refined analysis
  63. Fermi trigger No 644449593: Global MASTER-Net observations report
  64. Swift J1555.2-5402: Swift XRT refined analysis of the new SGR
  65. NICER discovery of 3.86 s pulsations from a new magnetar: SGR J1555.2-5402
  66. Swift Detection of probable new Swift SGR J1555.2-5402
  67. MAXI GRB210602.50: Global MASTER-Net observations report
  68. Swift GRB210603.41: Global MASTER-Net observations report
  69. GRB 210602A: CALET Gamma-Ray Burst Monitor detection
  70. GRB 210602B: GECAM detection
  71. GRB 210529A: GECAM detection
  72. Fermi trigger No 644359567: Global MASTER-Net observations report
  73. GRB 210602A: MAXI/GSC detection
  74. Fermi GRB 210601A: Global MASTER-Net observations report
  75. GRB 210601A: Fermi GBM Final Real-time Localization
  76. IPN triangulation of GRB 210531A
  77. GRB210529B: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 644025222)
  78. GRB 210531A: AstroSat CZTI detection
  79. Fermi trigger No 644155206: Global MASTER-Net observations report
  80. GRB 210531A: AGILE/MCAL detection (Fermi Trigger 644155206 / GRB 210531500)
  81. GRB 210531A: BALROG localization (Fermi Trigger 644155206 / GRB 210531500)
  82. GRB 210529B: DDOTI Upper Limits on the Afterglow
  83. Fermi GRB 210529A: Global MASTER-Net observations report
  84. Fermi GRB 210529B: Global MASTER-Net observations report
  85. GRB 210529B: Fermi GBM Final Real-time Localization
  86. GRB 210529A: Fermi GBM Final Real-time Localization
  87. GRB 210528A: Fermi GBM detection
  88. GRB 210528A: AstroSat CZTI detection
  89. GRB 210528B: DDOTI Upper Limits on the Afterglow
  90. GRB 210528B: MITSuME Akeno optical upper limits
  91. MAXI GRB210528.95: Global MASTER-Net observations report
  92. GRB 210528B: MAXI/GSC detection
  93. Fermi GRB 210528A: Global MASTER-Net observations report
  94. GRB 210527A: Swift-BAT refined analysis
  95. GRB 210528A: BALROG localization (Fermi Trigger 643903431 / GRB 210528586)
  96. GRB 210528A: Fermi GBM Final Real-time Localization
  97. GRB 210527A: Swift/UVOT Observations
  98. GRB 210527A: GIT optical upper limit
  99. GRB 210527A: MITSuME Akeno optical upper limits
  100. Swift GRB 210527A: Global MASTER-Net observations report

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