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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 210706A: Swift/BAT-GUANO detection and arcminute localization
  2. GRB 210704A: OSIRIS/GTC spectroscopy
  3. GRB 210704A: CAHA 2.2m Afterglow Detection
  4. GRB 210704A: RATIR optical upper limits
  5. GRB 210704A: Swift/UVOT Upper Limits
  6. Konus-Wind detection of GRB 210704A
  7. GRB 210704B: AstroSat CZTI detection
  8. GRB 210619B: ALMA detection
  9. GRB 210704A: TNG detection of the optical afterglow candidate
  10. GRB 210704A: Assy optical afterglow candidate
  11. GRB 210704A: DDOTI upper limit
  12. GRB 210704B: Fermi GBM detection
  13. GRB 210704A: possible local hosts
  14. GRB 210704A: Fermi GBM detection
  15. GRB 210704A: Swift-XRT afterglow detection
  16. GRB 210704A: AstroSat CZTI detection
  17. IceCube-210516A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  18. IceCube-210510A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  19. GRB 210704A: Fermi-LAT detection
  20. GRB 210704A: Swift ToO observations
  21. GRB 210705A: AGILE/MCAL detection of a burst
  22. GRB 210704A: AGILE/MCAL detection
  23. Fermi trigger No 647108723: Global MASTER-Net observations report
  24. Fermi trigger No 647120009: Global MASTER-Net observations report
  25. GRB 210704A: BALROG localization (Fermi Trigger 647120009 / GRB 210704815)
  26. GRB 210702A, Swift-BAT refined analysis
  27. GRB 210702A: BOOTES-3/YA optical counterpart observations
  28. Konus-Wind detection of GRB 210702A
  29. GRB 210702A: Chilescope optical observations
  30. GRB 210702A: iTelescope optical afterglow observations
  31. GRB 210702A: AGILE detection
  32. GRB 210702A: CALET Gamma-Ray Burst Monitor detection
  33. GRB 210619B: JCMT SCUBA-2 sub-mm observations
  34. GRB 210610B: JCMT SCUBA-2 sub-mm observations
  35. GRB 210610A: JCMT SCUBA-2 sub-mm observations
  36. GRB 210702A: Swift-XRT refined Analysis
  37. GRB 210702A: VLT/X-shooter redshift
  38. GRB 210702A: preliminary Swift/UVOT photometry
  39. GRB 210702A: Swift/UVOT redshift
  40. GRB210702A: MeerLICHT multi-colour photometry
  41. Swift GRB 210702A: Global MASTER-Net observations report
  42. Swift GRB210702.80: Global MASTER-Net OT detection
  43. GRB 210702A: Swift detection of a burst with a bright optical counterpart
  44. IceCube-210629A: Upper limits from a search for additional neutrino events in IceCube
  45. IceCube-210629A: One Candidate Counterpart from the Zwicky Transient Facility
  46. IceCube-210629A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  47. Fermi-LAT Gamma-ray Observations of IceCube-210629A
  48. IceCube-210629A: Upper limits from Fermi-GBM Observations
  49. GRB 210627B: GECAM detection
  50. IceCube Alert 210629.76: Global MASTER-Net observations report
  51. GRB 210619B: Sayan observatory 1.6-m telescope observations
  52. IceCube-210629A - IceCube observation of a high-energy neutrino candidate track-like event
  53. GRB 210626A: Swift/XRT afterglow confirmation
  54. GRB 210626A: Fermi GBM observation
  55. GRB 210626A: CAHA 2.2m telescope optical limit
  56. GRB 210619B: Deep CAHA 2.2m detection and late-time light curve behavior
  57. GRB 210626A: Ondrejov D50 optical limit
  58. GRB 210626A: GIT optical upper limit
  59. Fermi trigger No 646443989: Global MASTER-Net observations report
  60. Fermi GRB 210627B: Global MASTER-Net observations report
  61. GRB 210627B: BALROG localization (Fermi Trigger 646509445/ GRB 210627748)
  62. GRB 210627B: Fermi GBM Final Real-time Localization
  63. Fermi GRB 210627A: Global MASTER-Net observations report
  64. GRB 210627A: Fermi GBM Final Real-time Localization
  65. GRB 210626A: Swift-XRT afterglow detection
  66. Fermi trigger No 646322348: Global MASTER-Net observations report
  67. Fermi GRB 210626A: Global MASTER-Net observations report
  68. GRB 210626A: Swift ToO observations
  69. GRB 210626A: Swift/BAT-GUANO detection and arcminute localization
  70. GRB 150428A: late-time radio observations
  71. GRB 210626A: Fermi GBM Final Real-time Localization
  72. GRB 210618A: 1.5m OSN optical upper limit
  73. Fermi GRB 210625A: Global MASTER-Net observations report
  74. GRB210619B: optical afterglow detection from Konkoly Observatory
  75. GRB 210625A: Fermi GBM Final Real-time Localization
  76. IPN triangulation of GRB 210624A (short)
  77. GRB 210622A: Swift-XRT observations
  78. GRB 210610B: T-CAT optical observations
  79. GRB 210619B: ASIM observation
  80. Fermi trigger No 646189108: Global MASTER-Net observations report
  81. Fermi GBM observation of a bright burst in the direction of SGR 1935+2154
  82. GRB 210618A: Swift-XRT afterglow detection
  83. Fermi trigger No 646194855: Global MASTER-Net observations report
  84. GRB 210622A: Swift ToO observations
  85. GRB 210619B: Even further SAO RAS optical observations
  86. GRB 210619B: Mini-MegaTORTORA early optical observations
  87. Fermi GRB 210622B: Global MASTER-Net observations report
  88. GRB 210622A: Fermi GBM detection
  89. GRB 210619B: Abbey Ridge Observatory optical afterglow observation
  90. GRB 210619B: SPI-ACS/INTEGRAL observations
  91. GRB 210619B: Further SAO RAS optical observations
  92. GRB 210622A: Swift/BAT-GUANO detection and arcminute localization of a long burst
  93. GRB 210619B: possibility of lensed visible afterglow?
  94. GECAM detection of GRB 210622B
  95. GRB 210619B: AbAO optical observations
  96. GRB 210622B: Fermi GBM Final Real-time Localization
  97. GRB 210622A: Fermi GBM Final Real-time Localization
  98. Swift Trigger 1057131: detection of a burst from SGR Swift J1555.2-5402
  99. Swift GRB210621.71: Global MASTER-Net observations report
  100. GRB 210619B: NOT optical observations

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