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

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