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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 210531A: AstroSat CZTI detection
  2. Fermi trigger No 644155206: Global MASTER-Net observations report
  3. GRB 210531A: AGILE/MCAL detection (Fermi Trigger 644155206 / GRB 210531500)
  4. GRB 210531A: BALROG localization (Fermi Trigger 644155206 / GRB 210531500)
  5. GRB 210529B: DDOTI Upper Limits on the Afterglow
  6. Fermi GRB 210529A: Global MASTER-Net observations report
  7. Fermi GRB 210529B: Global MASTER-Net observations report
  8. GRB 210529B: Fermi GBM Final Real-time Localization
  9. GRB 210529A: Fermi GBM Final Real-time Localization
  10. GRB 210528A: Fermi GBM detection
  11. GRB 210528A: AstroSat CZTI detection
  12. GRB 210528B: DDOTI Upper Limits on the Afterglow
  13. GRB 210528B: MITSuME Akeno optical upper limits
  14. MAXI GRB210528.95: Global MASTER-Net observations report
  15. GRB 210528B: MAXI/GSC detection
  16. Fermi GRB 210528A: Global MASTER-Net observations report
  17. GRB 210527A: Swift-BAT refined analysis
  18. GRB 210528A: BALROG localization (Fermi Trigger 643903431 / GRB 210528586)
  19. GRB 210528A: Fermi GBM Final Real-time Localization
  20. GRB 210527A: Swift/UVOT Observations
  21. GRB 210527A: GIT optical upper limit
  22. GRB 210527A: MITSuME Akeno optical upper limits
  23. Swift GRB 210527A: Global MASTER-Net observations report
  24. GRB 210527A: Swift-XRT refined Analysis
  25. GRB 210527A: RATIR Optical and NIR Observations
  26. GRB 210527A: Enhanced Swift-XRT position
  27. GRB 210527A: Swift-XRT observations
  28. GRB 210527A: Swift detection of a burst
  29. GRB 210306A: LBT observations of the likely host galaxy
  30. ZTF21aayokph (AT2021lfa): LBT optical observations
  31. Fermi GRB 210524B: DDOTI Upper Limits on the Afterglow
  32. Konus-Wind detection of GRB 210524A
  33. IPN triangulation of GRB 210524A
  34. Fermi trigger No 643548039: Global MASTER-Net observations report
  35. GRB 210524B: Fermi GBM Final Real-time Localization
  36. GRB 210524A: BALROG localization (Fermi Trigger 643525204 / GRB 210524208)
  37. Fermi GRB 210524A: Global MASTER-Net observations report
  38. GRB 210524A: Fermi GBM Final Real-time Localization
  39. GRB 210522A: GECAM detection
  40. GRB 210520A: Swift-XRT observations
  41. MAXI GRB210521.54: Global MASTER-Net observations report
  42. GRB 210521A: MAXI/GSC detection
  43. GRB210413B: further Swift-XRT observations
  44. GRB 210520A: Fermi GBM detection
  45. ZTF21aayokph (AT2021lfa): continued Assy optical observations
  46. GRB 210520A: Tiled Swift observations
  47. GRB 210520A: Fermi-LAT detection
  48. GRB 210520A: GECAM detection
  49. Fermi GRB 210520A: Global MASTER-Net observations report
  50. GRB 210520A: Fermi GBM Final Real-time Localization
  51. Fermi GBM observation of a bright burst from magneta
  52. GRB 210517A: KCT optical upper limit
  53. IceCube GCN alert 135302_36915486.amon retraction
  54. Fermi GRB 210519A: Global MASTER-Net observations report
  55. IceCube Alert 210519.86: Global MASTER-Net observations report
  56. IPN triangulation of GRB 210518A
  57. Fermi trigger No 643065622: Global MASTER-Net observations report
  58. GRB 210518.889: DDOTI Upper Limits on the Afterglow
  59. GRB 210519A: Fermi GBM Final Localization
  60. Fermi GRB 210518A: Global MASTER-Net observations report
  61. Konus-Wind detection of GRB 210514A
  62. Fermi trigger No 642991619: Global MASTER-Net observations report
  63. Fermi-LAT Gamma-ray Observations of IceCube-210516A
  64. GRB 210518A: Fermi GBM Final Real-time Localization
  65. IceCube Alert 210515.01: Global MASTER-Net observations report
  66. GRB 210517A: Swift-BAT refined analysis
  67. GRB 210517A: Swift-XRT refined Analysis
  68. IceCube-210516A: No significant detection in HAWC
  69. GRB 210517A: Swift/UVOT Upper Limits
  70. GRB 210515C: Swift/UVOT Upper Limits
  71. IceCube-210516A: Upper limits from a search for additional neutrino events in IceCube
  72. GRB 210517A: VLT/X-shooter optical afterglow and redshift
  73. GRB 210517A: AGILE detection
  74. GRB 210514A: CALET Gamma-Ray Burst Monitor detection
  75. GRB 210517A: Enhanced Swift-XRT position
  76. Swift GRB 210517A: Global MASTER-Net observations report
  77. GRB 210517A: Swift detection of a burst
  78. Fermi GRB 210516A: Global MASTER-Net observations report
  79. GRB 210516A: Fermi GBM Final Real-time Localization
  80. IceCube Alert 210516.61: Global MASTER-Net observations report
  81. GRB 210515C: LCO Optical Upper Limit
  82. GRB 210504A: LCO Optical Afterglow Detection
  83. IceCube-210516A - IceCube observation of a high-energy neutrino candidate track-like event
  84. GRB 210514A: Swift/UVOT Upper Limits
  85. AMON IC_HAWC NuEm-210515A / NuEm-210515B : No neutrino counterpart detected with ANTARES
  86. GRB 210515C: Swift-XRT refined Analysis
  87. Swift GRB210515.83: Global MASTER-Net observations report
  88. GRB 210515C: Swift-BAT refined analysis
  89. GRB 210515C: Swift detection of a burst
  90. Fermi GRB 210515B: Global MASTER-Net observations report
  91. GRB 210514A: Swift-BAT refined analysis
  92. Fermi GRB 210515A: Global MASTER-Net observations report
  93. GRB 210515B: Fermi GBM Final Real-time Localization
  94. GRB 210515A: Fermi GBM Final Real-time Localization
  95. Swift GRB210514.71: Global MASTER-Net observations report
  96. GRB 210514A: Swift XRT light curve is fading
  97. GRB 210514A: Swift-XRT refined Analysis
  98. GRB 210514A: Enhanced Swift-XRT position
  99. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEM-210515A and 210515B
  100. GRB 210514A: update on the BAT trigger time and burst duration

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