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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: TNG detection of the optical afterglow candidate
  2. GRB 210704A: Assy optical afterglow candidate
  3. GRB 210704A: DDOTI upper limit
  4. GRB 210704B: Fermi GBM detection
  5. GRB 210704A: possible local hosts
  6. GRB 210704A: Fermi GBM detection
  7. GRB 210704A: Swift-XRT afterglow detection
  8. GRB 210704A: AstroSat CZTI detection
  9. IceCube-210516A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  10. IceCube-210510A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  11. GRB 210704A: Fermi-LAT detection
  12. GRB 210704A: Swift ToO observations
  13. GRB 210705A: AGILE/MCAL detection of a burst
  14. GRB 210704A: AGILE/MCAL detection
  15. Fermi trigger No 647108723: Global MASTER-Net observations report
  16. Fermi trigger No 647120009: Global MASTER-Net observations report
  17. GRB 210704A: BALROG localization (Fermi Trigger 647120009 / GRB 210704815)
  18. GRB 210702A, Swift-BAT refined analysis
  19. GRB 210702A: BOOTES-3/YA optical counterpart observations
  20. Konus-Wind detection of GRB 210702A
  21. GRB 210702A: Chilescope optical observations
  22. GRB 210702A: iTelescope optical afterglow observations
  23. GRB 210702A: AGILE detection
  24. GRB 210702A: CALET Gamma-Ray Burst Monitor detection
  25. GRB 210619B: JCMT SCUBA-2 sub-mm observations
  26. GRB 210610B: JCMT SCUBA-2 sub-mm observations
  27. GRB 210610A: JCMT SCUBA-2 sub-mm observations
  28. GRB 210702A: Swift-XRT refined Analysis
  29. GRB 210702A: VLT/X-shooter redshift
  30. GRB 210702A: preliminary Swift/UVOT photometry
  31. GRB 210702A: Swift/UVOT redshift
  32. GRB210702A: MeerLICHT multi-colour photometry
  33. Swift GRB 210702A: Global MASTER-Net observations report
  34. Swift GRB210702.80: Global MASTER-Net OT detection
  35. GRB 210702A: Swift detection of a burst with a bright optical counterpart
  36. IceCube-210629A: Upper limits from a search for additional neutrino events in IceCube
  37. IceCube-210629A: One Candidate Counterpart from the Zwicky Transient Facility
  38. IceCube-210629A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  39. Fermi-LAT Gamma-ray Observations of IceCube-210629A
  40. IceCube-210629A: Upper limits from Fermi-GBM Observations
  41. GRB 210627B: GECAM detection
  42. IceCube Alert 210629.76: Global MASTER-Net observations report
  43. GRB 210619B: Sayan observatory 1.6-m telescope observations
  44. IceCube-210629A - IceCube observation of a high-energy neutrino candidate track-like event
  45. GRB 210626A: Swift/XRT afterglow confirmation
  46. GRB 210626A: Fermi GBM observation
  47. GRB 210626A: CAHA 2.2m telescope optical limit
  48. GRB 210619B: Deep CAHA 2.2m detection and late-time light curve behavior
  49. GRB 210626A: Ondrejov D50 optical limit
  50. GRB 210626A: GIT optical upper limit
  51. Fermi trigger No 646443989: Global MASTER-Net observations report
  52. Fermi GRB 210627B: Global MASTER-Net observations report
  53. GRB 210627B: BALROG localization (Fermi Trigger 646509445/ GRB 210627748)
  54. GRB 210627B: Fermi GBM Final Real-time Localization
  55. Fermi GRB 210627A: Global MASTER-Net observations report
  56. GRB 210627A: Fermi GBM Final Real-time Localization
  57. GRB 210626A: Swift-XRT afterglow detection
  58. Fermi trigger No 646322348: Global MASTER-Net observations report
  59. Fermi GRB 210626A: Global MASTER-Net observations report
  60. GRB 210626A: Swift ToO observations
  61. GRB 210626A: Swift/BAT-GUANO detection and arcminute localization
  62. GRB 150428A: late-time radio observations
  63. GRB 210626A: Fermi GBM Final Real-time Localization
  64. GRB 210618A: 1.5m OSN optical upper limit
  65. Fermi GRB 210625A: Global MASTER-Net observations report
  66. GRB210619B: optical afterglow detection from Konkoly Observatory
  67. GRB 210625A: Fermi GBM Final Real-time Localization
  68. IPN triangulation of GRB 210624A (short)
  69. GRB 210622A: Swift-XRT observations
  70. GRB 210610B: T-CAT optical observations
  71. GRB 210619B: ASIM observation
  72. Fermi trigger No 646189108: Global MASTER-Net observations report
  73. Fermi GBM observation of a bright burst in the direction of SGR 1935+2154
  74. GRB 210618A: Swift-XRT afterglow detection
  75. Fermi trigger No 646194855: Global MASTER-Net observations report
  76. GRB 210622A: Swift ToO observations
  77. GRB 210619B: Even further SAO RAS optical observations
  78. GRB 210619B: Mini-MegaTORTORA early optical observations
  79. Fermi GRB 210622B: Global MASTER-Net observations report
  80. GRB 210622A: Fermi GBM detection
  81. GRB 210619B: Abbey Ridge Observatory optical afterglow observation
  82. GRB 210619B: SPI-ACS/INTEGRAL observations
  83. GRB 210619B: Further SAO RAS optical observations
  84. GRB 210622A: Swift/BAT-GUANO detection and arcminute localization of a long burst
  85. GRB 210619B: possibility of lensed visible afterglow?
  86. GECAM detection of GRB 210622B
  87. GRB 210619B: AbAO optical observations
  88. GRB 210622B: Fermi GBM Final Real-time Localization
  89. GRB 210622A: Fermi GBM Final Real-time Localization
  90. Swift Trigger 1057131: detection of a burst from SGR Swift J1555.2-5402
  91. Swift GRB210621.71: Global MASTER-Net observations report
  92. GRB 210619B: NOT optical observations
  93. GRB 210619B: 1.5m OSN optical observation
  94. GRB 210619B: iTelescope optical afterglow observation
  95. GRB 210619B: SAO RAS optical observations
  96. GRB 210619B: SEDM Optical Observations
  97. GRB 210619B: TNG NIR observations of the afterglow
  98. GRB 210619B: REM optical/NIR afterglow detection
  99. Fermi GRB 210621A: Global MASTER-Net observations report
  100. GRB 210619B: GIT optical follow-up and confirmation of jet-break

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