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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. Fermi GRB 210606A: DDOTI Upper Limits on the Afterglow
  2. GRB 210606A: Swift/BAT-GUANO detection and arcminute localization
  3. GRB 210605B: Swift ToO observations
  4. Fermi GRB 210606A: Global MASTER-Net observations report
  5. GRB 210606A: Fermi GBM Final Real-time Localization
  6. GRB 210605B: Swift/BAT-GUANO detection and arcminute localization
  7. GRB 210605B: Fermi GBM Final Real-time Localization
  8. Fermi GRB 210605A: Global MASTER-Net observations report
  9. GRB 210605A: Fermi GBM Final Real-time Localization
  10. Initial results of a NICER X-ray monitoring of the magnetar, Swift J1555.2-5402
  11. Fermi GBM Sub-Threshold Detection of new Swift SGR J1555.2-5402
  12. SGR J1555.2-5402: Swift-BAT refined analysis
  13. Fermi trigger No 644449593: Global MASTER-Net observations report
  14. Swift J1555.2-5402: Swift XRT refined analysis of the new SGR
  15. NICER discovery of 3.86 s pulsations from a new magnetar: SGR J1555.2-5402
  16. Swift Detection of probable new Swift SGR J1555.2-5402
  17. MAXI GRB210602.50: Global MASTER-Net observations report
  18. Swift GRB210603.41: Global MASTER-Net observations report
  19. GRB 210602A: CALET Gamma-Ray Burst Monitor detection
  20. GRB 210602B: GECAM detection
  21. GRB 210529A: GECAM detection
  22. Fermi trigger No 644359567: Global MASTER-Net observations report
  23. GRB 210602A: MAXI/GSC detection
  24. Fermi GRB 210601A: Global MASTER-Net observations report
  25. GRB 210601A: Fermi GBM Final Real-time Localization
  26. IPN triangulation of GRB 210531A
  27. GRB210529B: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 644025222)
  28. GRB 210531A: AstroSat CZTI detection
  29. Fermi trigger No 644155206: Global MASTER-Net observations report
  30. GRB 210531A: AGILE/MCAL detection (Fermi Trigger 644155206 / GRB 210531500)
  31. GRB 210531A: BALROG localization (Fermi Trigger 644155206 / GRB 210531500)
  32. GRB 210529B: DDOTI Upper Limits on the Afterglow
  33. Fermi GRB 210529A: Global MASTER-Net observations report
  34. Fermi GRB 210529B: Global MASTER-Net observations report
  35. GRB 210529B: Fermi GBM Final Real-time Localization
  36. GRB 210529A: Fermi GBM Final Real-time Localization
  37. GRB 210528A: Fermi GBM detection
  38. GRB 210528A: AstroSat CZTI detection
  39. GRB 210528B: DDOTI Upper Limits on the Afterglow
  40. GRB 210528B: MITSuME Akeno optical upper limits
  41. MAXI GRB210528.95: Global MASTER-Net observations report
  42. GRB 210528B: MAXI/GSC detection
  43. Fermi GRB 210528A: Global MASTER-Net observations report
  44. GRB 210527A: Swift-BAT refined analysis
  45. GRB 210528A: BALROG localization (Fermi Trigger 643903431 / GRB 210528586)
  46. GRB 210528A: Fermi GBM Final Real-time Localization
  47. GRB 210527A: Swift/UVOT Observations
  48. GRB 210527A: GIT optical upper limit
  49. GRB 210527A: MITSuME Akeno optical upper limits
  50. Swift GRB 210527A: Global MASTER-Net observations report
  51. GRB 210527A: Swift-XRT refined Analysis
  52. GRB 210527A: RATIR Optical and NIR Observations
  53. GRB 210527A: Enhanced Swift-XRT position
  54. GRB 210527A: Swift-XRT observations
  55. GRB 210527A: Swift detection of a burst
  56. GRB 210306A: LBT observations of the likely host galaxy
  57. ZTF21aayokph (AT2021lfa): LBT optical observations
  58. Fermi GRB 210524B: DDOTI Upper Limits on the Afterglow
  59. Konus-Wind detection of GRB 210524A
  60. IPN triangulation of GRB 210524A
  61. Fermi trigger No 643548039: Global MASTER-Net observations report
  62. GRB 210524B: Fermi GBM Final Real-time Localization
  63. GRB 210524A: BALROG localization (Fermi Trigger 643525204 / GRB 210524208)
  64. Fermi GRB 210524A: Global MASTER-Net observations report
  65. GRB 210524A: Fermi GBM Final Real-time Localization
  66. GRB 210522A: GECAM detection
  67. GRB 210520A: Swift-XRT observations
  68. MAXI GRB210521.54: Global MASTER-Net observations report
  69. GRB 210521A: MAXI/GSC detection
  70. GRB210413B: further Swift-XRT observations
  71. GRB 210520A: Fermi GBM detection
  72. ZTF21aayokph (AT2021lfa): continued Assy optical observations
  73. GRB 210520A: Tiled Swift observations
  74. GRB 210520A: Fermi-LAT detection
  75. GRB 210520A: GECAM detection
  76. Fermi GRB 210520A: Global MASTER-Net observations report
  77. GRB 210520A: Fermi GBM Final Real-time Localization
  78. Fermi GBM observation of a bright burst from magneta
  79. GRB 210517A: KCT optical upper limit
  80. IceCube GCN alert 135302_36915486.amon retraction
  81. Fermi GRB 210519A: Global MASTER-Net observations report
  82. IceCube Alert 210519.86: Global MASTER-Net observations report
  83. IPN triangulation of GRB 210518A
  84. Fermi trigger No 643065622: Global MASTER-Net observations report
  85. GRB 210518.889: DDOTI Upper Limits on the Afterglow
  86. GRB 210519A: Fermi GBM Final Localization
  87. Fermi GRB 210518A: Global MASTER-Net observations report
  88. Konus-Wind detection of GRB 210514A
  89. Fermi trigger No 642991619: Global MASTER-Net observations report
  90. Fermi-LAT Gamma-ray Observations of IceCube-210516A
  91. GRB 210518A: Fermi GBM Final Real-time Localization
  92. IceCube Alert 210515.01: Global MASTER-Net observations report
  93. GRB 210517A: Swift-BAT refined analysis
  94. GRB 210517A: Swift-XRT refined Analysis
  95. IceCube-210516A: No significant detection in HAWC
  96. GRB 210517A: Swift/UVOT Upper Limits
  97. GRB 210515C: Swift/UVOT Upper Limits
  98. IceCube-210516A: Upper limits from a search for additional neutrino events in IceCube
  99. GRB 210517A: VLT/X-shooter optical afterglow and redshift
  100. GRB 210517A: AGILE detection

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