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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 210323A: Fermi GBM detection
  2. GRB 210323A: Mondy optical observations, counterpart detection
  3. GRB 210324A: Fermi GBM Final Real-time Localization
  4. GRB 210318A: Swift/UVOT Upper Limits
  5. GRB 210323A: Swift-XRT refined Analysis
  6. GRB 210323A: Enhanced Swift-XRT position
  7. GRB 210323A: NOT optical afterglow candidate
  8. Swift GRB 210323A: Global MASTER-Net observations report
  9. GRB 210323B: Swift/BAT-GUANO detection and possible arcminute localization
  10. GRB 210323A: Nanshan/NEXT optical upper limit
  11. GRB 210323A: Swift detection of a short burst
  12. Fermi GBM trigger 637977270/210320996 is not a GRB
  13. GRB 210321A: Swift/UVOT Detection
  14. Konus-Wind detection of GRB 210321A
  15. GRB 210318B: Swift/UVOT Upper Limits
  16. GRB 210321A: DDOTI Position Correction
  17. IceCube Alert 210322.11: Global MASTER-Net observations report
  18. GRB 210321A: CrAO optical upper limit
  19. GRB 210321A: Swift-BAT refined analysis
  20. IceCube 135113_19489408.amon: Swift-XRT observations
  21. GRB 210321A: Mondy optical observations
  22. IceCube Astrotrack Bronze 135113_19489408.amon is likely background
  23. GRB 210321A: Xinglong GWAC-F60A optical observation
  24. GRB 210321A: Swift-XRT refined Analysis
  25. GRB 210321A: Redshift from OSIRIS/GTC
  26. GRB 210321A: NOT optical afterglow detection and redshift limit
  27. GRB 210321A: MASTER optical observation
  28. MAXI GRB210320.89: Global MASTER-Net observations report
  29. GRB 210321A: Enhanced Swift-XRT position
  30. GRB 210321A: DDOTI Afterglow Confirmation
  31. GRB 210321A: Swift/UVOT Detection
  32. GRB 210321A: Swift-XRT observations
  33. GRB 210321A: Swift detection of a burst
  34. GRB 210320A: MAXI/GSC detection
  35. GRB 210318B: MITSuME Okayama optical upper limits
  36. GRB 201216C: VIRT optical observations
  37. GRB 200524A: Redshift from Gemini-North
  38. GRB 210318A: Swift-BAT refined analysis
  39. GRB 210318A: Swift-XRT refined Analysis
  40. GRB 210318A: Enhanced Swift-XRT position
  41. Swift GRB210318.13: Global MASTER-Net observations report
  42. GRB 210318B: Fermi GBM detection
  43. Fermi trigger No 637729731: Global MASTER-Net observations report
  44. GRB 210318B: Swift-BAT refined analysis
  45. Swift GRB 210318A: Global MASTER-Net observations report
  46. Konus-Wind detection of GRB 210318B
  47. GRB210318B: Swift detection of a burst
  48. GRB 210318A: Swift detection of a burst
  49. Fermi GRB 210317A: Global MASTER-Net observations report
  50. GRB 210317A: GECAM detection
  51. GRB 210317A: Fermi GBM Final Real-time Localization
  52. Fermi trigger No 637521056: Global MASTER-Net observations report
  53. GRB 210306A: GIT optical follow-up
  54. GRB 210226A: GIT optical upper limit
  55. GRB 210312B: Redshift from OSIRIS/GTC
  56. GRB 210306A: HCT optical upper limit
  57. GRB 210312B: GTC photometry
  58. GRB 210312B: MASTER OT confirmation
  59. GRB210312B (Integral alert 9073): Candidate optical afterglow by Ondrejov D50
  60. GRB 210312B: A long GRB detected by INTEGRAL
  61. Integral GRB210312.87: Global MASTER-Net observations report
  62. Fermi GRB 210312A: Global MASTER-Net observations report
  63. INTEGRAL SPI-ACS on 2021-03-12 (04)11-08:15) are due to calibration activity
  64. GRB 210312A: Fermi GBM Final Real-time Localization
  65. GRB 210306A: LBT observations
  66. GRB 210306A: Tautenburg observations
  67. Konus-Wind detection of GRB 210308A
  68. Konus-Wind detection of GRB 210306A
  69. Konus-Wind detection of GRB 210305A
  70. GRB 171205A: Continued ATCA observations
  71. Fermi trigger No 637027080: Global MASTER-Net observations report
  72. GRB 210306A: Early Spectroscopy of the Optical Afterglow
  73. GRB 210306B: Fermi GBM detection
  74. GRB 210306A: Swift/UVOT Detection
  75. GRB 210306A: continued Mondy optical observations
  76. GRB 210308A: Mondy and AbAO optical observations
  77. GRB 210308A: Swift-BAT refined analysis
  78. GRB 210307A: Swift-BAT refined analysis
  79. Fermi trigger No 636926765: Global MASTER-Net observations report
  80. GRB 210308A: Swift/UVOT Detection
  81. GRB 210307A: Swift/UVOT Upper Limits
  82. GRB 210305A: Fermi GBM observation
  83. Swift GRB 210308A: Global MASTER-Net observations report
  84. GRB 210308A: Fermi GBM detection
  85. GRB 210305A: Swift-XRT refined Analysis
  86. GRB 210307A: Swift-XRT refined Analysis
  87. GRB 210308A: Nanshan/NEXT optical upper limits
  88. GRB 210306A: Swift-XRT refined Analysis
  89. GRB 210308A: MITSuME Okayama optical upper limits
  90. GRB 210306A: continued Mondy optical observations
  91. GRB 210308A: Swift detection of a burst with an optical counterpart
  92. GRB 210306A: 1.3m DFOT observations
  93. GRB 210306A: Swift-BAT refined analysis
  94. GRB 210306A: Mondy optical observations
  95. GRB 210305A: Swift/UVOT Upper Limits
  96. GRB 210307B: GECAM detection
  97. GRB 210307A: LCO Optical Upper Limits
  98. GRB 210306B: Swift-BAT refined analysis
  99. GRB 210305A: Swift-BAT refined analysis
  100. GRB 210307A: Swift detection of a burst

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