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

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