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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 210528A: Global MASTER-Net observations report
  2. GRB 210527A: Swift-BAT refined analysis
  3. GRB 210528A: BALROG localization (Fermi Trigger 643903431 / GRB 210528586)
  4. GRB 210528A: Fermi GBM Final Real-time Localization
  5. GRB 210527A: Swift/UVOT Observations
  6. GRB 210527A: GIT optical upper limit
  7. GRB 210527A: MITSuME Akeno optical upper limits
  8. Swift GRB 210527A: Global MASTER-Net observations report
  9. GRB 210527A: Swift-XRT refined Analysis
  10. GRB 210527A: RATIR Optical and NIR Observations
  11. GRB 210527A: Enhanced Swift-XRT position
  12. GRB 210527A: Swift-XRT observations
  13. GRB 210527A: Swift detection of a burst
  14. GRB 210306A: LBT observations of the likely host galaxy
  15. ZTF21aayokph (AT2021lfa): LBT optical observations
  16. Fermi GRB 210524B: DDOTI Upper Limits on the Afterglow
  17. Konus-Wind detection of GRB 210524A
  18. IPN triangulation of GRB 210524A
  19. Fermi trigger No 643548039: Global MASTER-Net observations report
  20. GRB 210524B: Fermi GBM Final Real-time Localization
  21. GRB 210524A: BALROG localization (Fermi Trigger 643525204 / GRB 210524208)
  22. Fermi GRB 210524A: Global MASTER-Net observations report
  23. GRB 210524A: Fermi GBM Final Real-time Localization
  24. GRB 210522A: GECAM detection
  25. GRB 210520A: Swift-XRT observations
  26. MAXI GRB210521.54: Global MASTER-Net observations report
  27. GRB 210521A: MAXI/GSC detection
  28. GRB210413B: further Swift-XRT observations
  29. GRB 210520A: Fermi GBM detection
  30. ZTF21aayokph (AT2021lfa): continued Assy optical observations
  31. GRB 210520A: Tiled Swift observations
  32. GRB 210520A: Fermi-LAT detection
  33. GRB 210520A: GECAM detection
  34. Fermi GRB 210520A: Global MASTER-Net observations report
  35. GRB 210520A: Fermi GBM Final Real-time Localization
  36. Fermi GBM observation of a bright burst from magneta
  37. GRB 210517A: KCT optical upper limit
  38. IceCube GCN alert 135302_36915486.amon retraction
  39. Fermi GRB 210519A: Global MASTER-Net observations report
  40. IceCube Alert 210519.86: Global MASTER-Net observations report
  41. IPN triangulation of GRB 210518A
  42. Fermi trigger No 643065622: Global MASTER-Net observations report
  43. GRB 210518.889: DDOTI Upper Limits on the Afterglow
  44. GRB 210519A: Fermi GBM Final Localization
  45. Fermi GRB 210518A: Global MASTER-Net observations report
  46. Konus-Wind detection of GRB 210514A
  47. Fermi trigger No 642991619: Global MASTER-Net observations report
  48. Fermi-LAT Gamma-ray Observations of IceCube-210516A
  49. GRB 210518A: Fermi GBM Final Real-time Localization
  50. IceCube Alert 210515.01: Global MASTER-Net observations report
  51. GRB 210517A: Swift-BAT refined analysis
  52. GRB 210517A: Swift-XRT refined Analysis
  53. IceCube-210516A: No significant detection in HAWC
  54. GRB 210517A: Swift/UVOT Upper Limits
  55. GRB 210515C: Swift/UVOT Upper Limits
  56. IceCube-210516A: Upper limits from a search for additional neutrino events in IceCube
  57. GRB 210517A: VLT/X-shooter optical afterglow and redshift
  58. GRB 210517A: AGILE detection
  59. GRB 210514A: CALET Gamma-Ray Burst Monitor detection
  60. GRB 210517A: Enhanced Swift-XRT position
  61. Swift GRB 210517A: Global MASTER-Net observations report
  62. GRB 210517A: Swift detection of a burst
  63. Fermi GRB 210516A: Global MASTER-Net observations report
  64. GRB 210516A: Fermi GBM Final Real-time Localization
  65. IceCube Alert 210516.61: Global MASTER-Net observations report
  66. GRB 210515C: LCO Optical Upper Limit
  67. GRB 210504A: LCO Optical Afterglow Detection
  68. IceCube-210516A - IceCube observation of a high-energy neutrino candidate track-like event
  69. GRB 210514A: Swift/UVOT Upper Limits
  70. AMON IC_HAWC NuEm-210515A / NuEm-210515B : No neutrino counterpart detected with ANTARES
  71. GRB 210515C: Swift-XRT refined Analysis
  72. Swift GRB210515.83: Global MASTER-Net observations report
  73. GRB 210515C: Swift-BAT refined analysis
  74. GRB 210515C: Swift detection of a burst
  75. Fermi GRB 210515B: Global MASTER-Net observations report
  76. GRB 210514A: Swift-BAT refined analysis
  77. Fermi GRB 210515A: Global MASTER-Net observations report
  78. GRB 210515B: Fermi GBM Final Real-time Localization
  79. GRB 210515A: Fermi GBM Final Real-time Localization
  80. Swift GRB210514.71: Global MASTER-Net observations report
  81. GRB 210514A: Swift XRT light curve is fading
  82. GRB 210514A: Swift-XRT refined Analysis
  83. GRB 210514A: Enhanced Swift-XRT position
  84. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEM-210515A and 210515B
  85. GRB 210514A: update on the BAT trigger time and burst duration
  86. GRB 210514A: Swift detection of a burst
  87. Konus-Wind detection of GRB 210511B
  88. GRB 210512.786: DDOTI Upper Limits on the Afterglow
  89. GRB210510A: Optical afterglow candidate from the Zwicky Transient Facility
  90. Fermi trigger No 642538568: Global MASTER-Net observations report
  91. IceCube-210510A: Upper limits from a search for additional neutrino events in IceCube
  92. IPN triangulation of GRB 210511B
  93. IceCube-210510A: not observable by Fermi-GBM
  94. Short GRB 210323A: likely host galaxy detection
  95. IceCube-210510A: No candidate counterparts from the Zwicky Transient Facility
  96. GRB 210511B: DDOTI Upper Limits on the Afterglow
  97. IPN triangulation of GRB 210427A
  98. GRB 210511B: Fermi GBM observation
  99. Fermi-LAT Gamma-ray Observations of IceCube-210510A
  100. Fermi GRB 210511A: Global MASTER-Net observations report

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