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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 210318B: Swift/UVOT Upper Limits
  2. GRB 210321A: DDOTI Position Correction
  3. IceCube Alert 210322.11: Global MASTER-Net observations report
  4. GRB 210321A: CrAO optical upper limit
  5. GRB 210321A: Swift-BAT refined analysis
  6. IceCube 135113_19489408.amon: Swift-XRT observations
  7. GRB 210321A: Mondy optical observations
  8. IceCube Astrotrack Bronze 135113_19489408.amon is likely background
  9. GRB 210321A: Xinglong GWAC-F60A optical observation
  10. GRB 210321A: Swift-XRT refined Analysis
  11. GRB 210321A: Redshift from OSIRIS/GTC
  12. GRB 210321A: NOT optical afterglow detection and redshift limit
  13. GRB 210321A: MASTER optical observation
  14. MAXI GRB210320.89: Global MASTER-Net observations report
  15. GRB 210321A: Enhanced Swift-XRT position
  16. GRB 210321A: DDOTI Afterglow Confirmation
  17. GRB 210321A: Swift/UVOT Detection
  18. GRB 210321A: Swift-XRT observations
  19. GRB 210321A: Swift detection of a burst
  20. GRB 210320A: MAXI/GSC detection
  21. GRB 210318B: MITSuME Okayama optical upper limits
  22. GRB 201216C: VIRT optical observations
  23. GRB 200524A: Redshift from Gemini-North
  24. GRB 210318A: Swift-BAT refined analysis
  25. GRB 210318A: Swift-XRT refined Analysis
  26. GRB 210318A: Enhanced Swift-XRT position
  27. Swift GRB210318.13: Global MASTER-Net observations report
  28. GRB 210318B: Fermi GBM detection
  29. Fermi trigger No 637729731: Global MASTER-Net observations report
  30. GRB 210318B: Swift-BAT refined analysis
  31. Swift GRB 210318A: Global MASTER-Net observations report
  32. Konus-Wind detection of GRB 210318B
  33. GRB210318B: Swift detection of a burst
  34. GRB 210318A: Swift detection of a burst
  35. Fermi GRB 210317A: Global MASTER-Net observations report
  36. GRB 210317A: GECAM detection
  37. GRB 210317A: Fermi GBM Final Real-time Localization
  38. Fermi trigger No 637521056: Global MASTER-Net observations report
  39. GRB 210306A: GIT optical follow-up
  40. GRB 210226A: GIT optical upper limit
  41. GRB 210312B: Redshift from OSIRIS/GTC
  42. GRB 210306A: HCT optical upper limit
  43. GRB 210312B: GTC photometry
  44. GRB 210312B: MASTER OT confirmation
  45. GRB210312B (Integral alert 9073): Candidate optical afterglow by Ondrejov D50
  46. GRB 210312B: A long GRB detected by INTEGRAL
  47. Integral GRB210312.87: Global MASTER-Net observations report
  48. Fermi GRB 210312A: Global MASTER-Net observations report
  49. INTEGRAL SPI-ACS on 2021-03-12 (04)11-08:15) are due to calibration activity
  50. GRB 210312A: Fermi GBM Final Real-time Localization
  51. GRB 210306A: LBT observations
  52. GRB 210306A: Tautenburg observations
  53. Konus-Wind detection of GRB 210308A
  54. Konus-Wind detection of GRB 210306A
  55. Konus-Wind detection of GRB 210305A
  56. GRB 171205A: Continued ATCA observations
  57. Fermi trigger No 637027080: Global MASTER-Net observations report
  58. GRB 210306A: Early Spectroscopy of the Optical Afterglow
  59. GRB 210306B: Fermi GBM detection
  60. GRB 210306A: Swift/UVOT Detection
  61. GRB 210306A: continued Mondy optical observations
  62. GRB 210308A: Mondy and AbAO optical observations
  63. GRB 210308A: Swift-BAT refined analysis
  64. GRB 210307A: Swift-BAT refined analysis
  65. Fermi trigger No 636926765: Global MASTER-Net observations report
  66. GRB 210308A: Swift/UVOT Detection
  67. GRB 210307A: Swift/UVOT Upper Limits
  68. GRB 210305A: Fermi GBM observation
  69. Swift GRB 210308A: Global MASTER-Net observations report
  70. GRB 210308A: Fermi GBM detection
  71. GRB 210305A: Swift-XRT refined Analysis
  72. GRB 210307A: Swift-XRT refined Analysis
  73. GRB 210308A: Nanshan/NEXT optical upper limits
  74. GRB 210306A: Swift-XRT refined Analysis
  75. GRB 210308A: MITSuME Okayama optical upper limits
  76. GRB 210306A: continued Mondy optical observations
  77. GRB 210308A: Swift detection of a burst with an optical counterpart
  78. GRB 210306A: 1.3m DFOT observations
  79. GRB 210306A: Swift-BAT refined analysis
  80. GRB 210306A: Mondy optical observations
  81. GRB 210305A: Swift/UVOT Upper Limits
  82. GRB 210307B: GECAM detection
  83. GRB 210307A: LCO Optical Upper Limits
  84. GRB 210306B: Swift-BAT refined analysis
  85. GRB 210305A: Swift-BAT refined analysis
  86. GRB 210307A: Swift detection of a burst
  87. Swift GRB210307.36: Global MASTER-Net observations report
  88. GRB 210306A: MITSuME Akeno optical observation
  89. GRB 210306A: NEXT optical observations
  90. Swift GRB 210306A: Global MASTER-Net observations report
  91. GRB 210306A: Fermi GBM observation
  92. GRB 210306A: Tautenburg observations
  93. GRB 210306A: iTelescope T24 optical observations
  94. GRB 210306A: Fermi-LAT detection
  95. GRB 210306B: Swift detection of a burst
  96. GRB 210306A: LCO Optical Afterglow Detection
  97. GRB 210306A: iTelescope optical afterglow observations
  98. GRB 210306A: DDOTI Afterglow Confirmation
  99. GRB 210306A: Swift detection of a burst with a bright optical counterpart
  100. Swift GRB 210305A: Global MASTER-Net observations report

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