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

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