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

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