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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. GRB210529B: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 644025222)
  2. GRB 210531A: AstroSat CZTI detection
  3. Fermi trigger No 644155206: Global MASTER-Net observations report
  4. GRB 210531A: AGILE/MCAL detection (Fermi Trigger 644155206 / GRB 210531500)
  5. GRB 210531A: BALROG localization (Fermi Trigger 644155206 / GRB 210531500)
  6. GRB 210529B: DDOTI Upper Limits on the Afterglow
  7. Fermi GRB 210529A: Global MASTER-Net observations report
  8. Fermi GRB 210529B: Global MASTER-Net observations report
  9. GRB 210529B: Fermi GBM Final Real-time Localization
  10. GRB 210529A: Fermi GBM Final Real-time Localization
  11. GRB 210528A: Fermi GBM detection
  12. GRB 210528A: AstroSat CZTI detection
  13. GRB 210528B: DDOTI Upper Limits on the Afterglow
  14. GRB 210528B: MITSuME Akeno optical upper limits
  15. MAXI GRB210528.95: Global MASTER-Net observations report
  16. GRB 210528B: MAXI/GSC detection
  17. Fermi GRB 210528A: Global MASTER-Net observations report
  18. GRB 210527A: Swift-BAT refined analysis
  19. GRB 210528A: BALROG localization (Fermi Trigger 643903431 / GRB 210528586)
  20. GRB 210528A: Fermi GBM Final Real-time Localization
  21. GRB 210527A: Swift/UVOT Observations
  22. GRB 210527A: GIT optical upper limit
  23. GRB 210527A: MITSuME Akeno optical upper limits
  24. Swift GRB 210527A: Global MASTER-Net observations report
  25. GRB 210527A: Swift-XRT refined Analysis
  26. GRB 210527A: RATIR Optical and NIR Observations
  27. GRB 210527A: Enhanced Swift-XRT position
  28. GRB 210527A: Swift-XRT observations
  29. GRB 210527A: Swift detection of a burst
  30. GRB 210306A: LBT observations of the likely host galaxy
  31. ZTF21aayokph (AT2021lfa): LBT optical observations
  32. Fermi GRB 210524B: DDOTI Upper Limits on the Afterglow
  33. Konus-Wind detection of GRB 210524A
  34. IPN triangulation of GRB 210524A
  35. Fermi trigger No 643548039: Global MASTER-Net observations report
  36. GRB 210524B: Fermi GBM Final Real-time Localization
  37. GRB 210524A: BALROG localization (Fermi Trigger 643525204 / GRB 210524208)
  38. Fermi GRB 210524A: Global MASTER-Net observations report
  39. GRB 210524A: Fermi GBM Final Real-time Localization
  40. GRB 210522A: GECAM detection
  41. GRB 210520A: Swift-XRT observations
  42. MAXI GRB210521.54: Global MASTER-Net observations report
  43. GRB 210521A: MAXI/GSC detection
  44. GRB210413B: further Swift-XRT observations
  45. GRB 210520A: Fermi GBM detection
  46. ZTF21aayokph (AT2021lfa): continued Assy optical observations
  47. GRB 210520A: Tiled Swift observations
  48. GRB 210520A: Fermi-LAT detection
  49. GRB 210520A: GECAM detection
  50. Fermi GRB 210520A: Global MASTER-Net observations report
  51. GRB 210520A: Fermi GBM Final Real-time Localization
  52. Fermi GBM observation of a bright burst from magneta
  53. GRB 210517A: KCT optical upper limit
  54. IceCube GCN alert 135302_36915486.amon retraction
  55. Fermi GRB 210519A: Global MASTER-Net observations report
  56. IceCube Alert 210519.86: Global MASTER-Net observations report
  57. IPN triangulation of GRB 210518A
  58. Fermi trigger No 643065622: Global MASTER-Net observations report
  59. GRB 210518.889: DDOTI Upper Limits on the Afterglow
  60. GRB 210519A: Fermi GBM Final Localization
  61. Fermi GRB 210518A: Global MASTER-Net observations report
  62. Konus-Wind detection of GRB 210514A
  63. Fermi trigger No 642991619: Global MASTER-Net observations report
  64. Fermi-LAT Gamma-ray Observations of IceCube-210516A
  65. GRB 210518A: Fermi GBM Final Real-time Localization
  66. IceCube Alert 210515.01: Global MASTER-Net observations report
  67. GRB 210517A: Swift-BAT refined analysis
  68. GRB 210517A: Swift-XRT refined Analysis
  69. IceCube-210516A: No significant detection in HAWC
  70. GRB 210517A: Swift/UVOT Upper Limits
  71. GRB 210515C: Swift/UVOT Upper Limits
  72. IceCube-210516A: Upper limits from a search for additional neutrino events in IceCube
  73. GRB 210517A: VLT/X-shooter optical afterglow and redshift
  74. GRB 210517A: AGILE detection
  75. GRB 210514A: CALET Gamma-Ray Burst Monitor detection
  76. GRB 210517A: Enhanced Swift-XRT position
  77. Swift GRB 210517A: Global MASTER-Net observations report
  78. GRB 210517A: Swift detection of a burst
  79. Fermi GRB 210516A: Global MASTER-Net observations report
  80. GRB 210516A: Fermi GBM Final Real-time Localization
  81. IceCube Alert 210516.61: Global MASTER-Net observations report
  82. GRB 210515C: LCO Optical Upper Limit
  83. GRB 210504A: LCO Optical Afterglow Detection
  84. IceCube-210516A - IceCube observation of a high-energy neutrino candidate track-like event
  85. GRB 210514A: Swift/UVOT Upper Limits
  86. AMON IC_HAWC NuEm-210515A / NuEm-210515B : No neutrino counterpart detected with ANTARES
  87. GRB 210515C: Swift-XRT refined Analysis
  88. Swift GRB210515.83: Global MASTER-Net observations report
  89. GRB 210515C: Swift-BAT refined analysis
  90. GRB 210515C: Swift detection of a burst
  91. Fermi GRB 210515B: Global MASTER-Net observations report
  92. GRB 210514A: Swift-BAT refined analysis
  93. Fermi GRB 210515A: Global MASTER-Net observations report
  94. GRB 210515B: Fermi GBM Final Real-time Localization
  95. GRB 210515A: Fermi GBM Final Real-time Localization
  96. Swift GRB210514.71: Global MASTER-Net observations report
  97. GRB 210514A: Swift XRT light curve is fading
  98. GRB 210514A: Swift-XRT refined Analysis
  99. GRB 210514A: Enhanced Swift-XRT position
  100. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEM-210515A and 210515B

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