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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 210807C: Fermi GBM Final Real-time Localization
  2. Fermi GRB 210807B: Global MASTER-Net observations report
  3. Swift GRB 210807A: Global MASTER-Net observations report
  4. Swift GRB210807.79: Global MASTER-Net observations report
  5. Swift GRB210807.78: Global MASTER-Net observations report
  6. Fermi trigger No 650046564: Global MASTER-Net observations report
  7. GRB 210807A: Enhanced Swift-XRT position
  8. GRB 210807A: BOOTES-5/JGT optical afterglow detection
  9. GRB 210807B: Fermi GBM Final Real-time Localization
  10. GRB 210807A: Swift detection of a burst with an optical counterpart
  11. Konus-Wind detection of a burst from SGR 1935+2154 on 2021 August 5
  12. IPN Triangulation of a bright burst from SGR 1935+2154
  13. Fermi trigger No 649814537: Global MASTER-Net observations report
  14. GRB 210802A: MITSuME Okayama optical upper limits
  15. GRB 210803A: Fermi GBM observation
  16. Fermi trigger No 649684549: Global MASTER-Net observations report
  17. GRB 210802A: DDOTI Upper Limits
  18. GRB 210802A: BOOTES-2/TELMA optical upper limit
  19. GRB 210802A: Swift-XRT afterglow detection
  20. GRB 210802A: Fermi GBM detection
  21. GRB 210802A: Fermi-LAT detection
  22. GRB 210803A: BALROG localization (Fermi Trigger 649684549 / GRB 210803497)
  23. GRB 210802A: Tiled Swift observations
  24. Fermi trigger No 649627691: Global MASTER-Net observations report
  25. GRB 210801A: Fermi GBM detection
  26. GRB 210731A: continued GROND observations
  27. GRB 210731A: VLT/X-shooter redshift
  28. GRB 210731A: KAIT Optical Detection
  29. IceCube-210730A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  30. GRB 210731A: Swift-BAT refined analysis
  31. Fermi trigger No 649524889: Global MASTER-Net observations report
  32. GRB 210731A: MASTER optical afterglow detection
  33. GRB 210801A: BALROG localization (Fermi Trigger 649519043 / GRB 210801581)
  34. GRB 210731A: Swift-XRT refined Analysis
  35. Fermi trigger No 649519043: Global MASTER-Net observations report
  36. GRB 210731A: GROND observations
  37. GRB 210731A: Fermi GBM Observation
  38. GRB 210731A: Swift/UVOT Detection of an optical afterglow
  39. Swift GRB210731.62: Global MASTER-Net observations report
  40. GRB 210731A: MeerLICHT optical afterglow detection
  41. GRB210731A: Enhanced Swift-XRT position
  42. GRB 210731A: Swift detection of a burst
  43. Swift GRB210731.93: Global MASTER-Net observations report
  44. Fermi-LAT Gamma-ray Observations of IceCube-210730A
  45. Trigger 1062273: Swift detection of 4U 1700-377
  46. GRB 210730A: Campo Imperatore optical observations
  47. GRB 210730A: BOOTES-5/JGT and 2.2m CAHA telescopes optical limit
  48. Swift GRB 210730A: Global MASTER-Net observations report
  49. Fermi trigger No 649390368: Global MASTER-Net observations report
  50. GRB 210730A: TNG optical observations
  51. IceCube-210730A - IceCube observation of a high-energy neutrino candidate track-like event
  52. GRB 210726A: Chandra detection of the X-ray afterglow
  53. GRB 210730A: Fermi GBM observation
  54. Fermi trigger No 649313854: Global MASTER-Net observations report
  55. GRB 210730A: AstroSat CZTI detection
  56. GRB 210730A: Swift-BAT refined analysis
  57. GRB 210730A: Swift-XRT refined Analysis
  58. GRB 210730A: Swift/UVOT Upper Limits
  59. GRB 210724A: Early CAHA 2.2m limit
  60. GRB 210730A: Enhanced Swift-XRT position
  61. GRB 210727A: AstroSat CZTI detection
  62. GRB 210730A: Swift detection of a burst near M82
  63. GRB 210724A: Corrected Swift-XRT enhanced position
  64. Fermi GBM Sub-Threshold Detection of GRB 210725B
  65. GRB 210726A: OSIRIS/GTC observations
  66. GRB 210727A: CALET Gamma-Ray Burst Monitor detection
  67. GRB 210726A: Deep CAHA 2.2m limit
  68. GRB 210726A: 6 GHz VLA radio upper limit
  69. IPN triangulation of GRB 210727A (short)
  70. Fermi GBM Sub-Threshold Detection of GRB 210726A
  71. GRB 210714A: Fermi GBM observation
  72. GRB 210702A: MeerKAT radio detection
  73. GRB 210726A: Swift-XRT refined Analysis
  74. GRB 210726A: Swift-BAT refined analysis
  75. GRB 210726A: Likely a short burst
  76. GRB 210726A: RATIR Optical Upper Limits and Candidate Host Galaxy
  77. GRB 210727A: AGILE/MCAL detection
  78. Fermi trigger No 649072251: Global MASTER-Net observations report
  79. GRB 210727A: BALROG localization (Fermi Trigger 649072251 / GRB 210727410)
  80. GRB 210725A: AbAO optical upper limit
  81. GRB 210724A: Swift/UVOT Upper Limits
  82. GRB 210723A: Swift/UVOT Upper Limits
  83. GRB 210725A: Swift/UVOT Upper Limits
  84. GRB 210725B: Swift/UVOT Upper Limits
  85. GRB 210726A: CAHA 2.2m telescope optical limit
  86. GRB 210726A: Enhanced Swift-XRT position
  87. GRB 210726A: Swift detection of a burst
  88. Swift GRB210726.80: Global MASTER-Net observations report
  89. Fermi trigger No 648959581: Global MASTER-Net observations report
  90. GRB 210725B: Swift-XRT refined Analysis
  91. GRB 210725A: Fermi GBM detection
  92. GRB 210724A: Zeiss-1000 of Koshka observatory, optical upper limit
  93. GRB 210725A: Swift-XRT refined Analysis
  94. GRB 210725B: Swift-BAT refined analysis
  95. GRB 210724A: Swift-XRT refined Analysis
  96. GRB 210725A: Swift-BAT refined analysis
  97. GRB 210724A: Swift-BAT refined analysis
  98. Swift GRB 210725B: Global MASTER-Net observations report
  99. GRB 210724A: Afterglow candidate from OSIRIS/GTC
  100. GRB 210725B: Enhanced Swift-XRT position

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