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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. Konus-Wind detection of a burst from SGR 1935+2154 on 2021 July 6
  2. Fermi trigger No 647271699: Global MASTER-Net observations report
  3. Fermi GBM Observations of SGR J1935+2154
  4. Swift-BAT detection of a burst from SGR 1935+2154
  5. GRB 210706A: Fermi GBM observation
  6. GRB 210706A: optical upper limit of Sintesz-Newton/CrAO and AS-32/AbAO
  7. Konus-Wind detection of GRB 210706A
  8. GRB 210706A: GIT optical upper limits
  9. GRB 210704A: OAJ T80 multi-color detections
  10. GECAM detection of a bright short burst from SGR 1935+2154
  11. GRB 210706A: Swift-XRT afterglow detection
  12. Integral GRB210707.02: Global MASTER-Net observations report
  13. GRB 210706A: Swift ToO observations
  14. Fermi trigger No 647252274: Global MASTER-Net observations report
  15. INTEGRAL detection of a burst from SGR 1935+2154
  16. Integral GRB210706.72: Global MASTER-Net observations report
  17. GRB 210706A: Swift/BAT-GUANO detection and arcminute localization
  18. GRB 210704A: OSIRIS/GTC spectroscopy
  19. GRB 210704A: CAHA 2.2m Afterglow Detection
  20. GRB 210704A: RATIR optical upper limits
  21. GRB 210704A: Swift/UVOT Upper Limits
  22. Konus-Wind detection of GRB 210704A
  23. GRB 210704B: AstroSat CZTI detection
  24. GRB 210619B: ALMA detection
  25. GRB 210704A: TNG detection of the optical afterglow candidate
  26. GRB 210704A: Assy optical afterglow candidate
  27. GRB 210704A: DDOTI upper limit
  28. GRB 210704B: Fermi GBM detection
  29. GRB 210704A: possible local hosts
  30. GRB 210704A: Fermi GBM detection
  31. GRB 210704A: Swift-XRT afterglow detection
  32. GRB 210704A: AstroSat CZTI detection
  33. IceCube-210516A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  34. IceCube-210510A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  35. GRB 210704A: Fermi-LAT detection
  36. GRB 210704A: Swift ToO observations
  37. GRB 210705A: AGILE/MCAL detection of a burst
  38. GRB 210704A: AGILE/MCAL detection
  39. Fermi trigger No 647108723: Global MASTER-Net observations report
  40. Fermi trigger No 647120009: Global MASTER-Net observations report
  41. GRB 210704A: BALROG localization (Fermi Trigger 647120009 / GRB 210704815)
  42. GRB 210702A, Swift-BAT refined analysis
  43. GRB 210702A: BOOTES-3/YA optical counterpart observations
  44. Konus-Wind detection of GRB 210702A
  45. GRB 210702A: Chilescope optical observations
  46. GRB 210702A: iTelescope optical afterglow observations
  47. GRB 210702A: AGILE detection
  48. GRB 210702A: CALET Gamma-Ray Burst Monitor detection
  49. GRB 210619B: JCMT SCUBA-2 sub-mm observations
  50. GRB 210610B: JCMT SCUBA-2 sub-mm observations
  51. GRB 210610A: JCMT SCUBA-2 sub-mm observations
  52. GRB 210702A: Swift-XRT refined Analysis
  53. GRB 210702A: VLT/X-shooter redshift
  54. GRB 210702A: preliminary Swift/UVOT photometry
  55. GRB 210702A: Swift/UVOT redshift
  56. GRB210702A: MeerLICHT multi-colour photometry
  57. Swift GRB 210702A: Global MASTER-Net observations report
  58. Swift GRB210702.80: Global MASTER-Net OT detection
  59. GRB 210702A: Swift detection of a burst with a bright optical counterpart
  60. IceCube-210629A: Upper limits from a search for additional neutrino events in IceCube
  61. IceCube-210629A: One Candidate Counterpart from the Zwicky Transient Facility
  62. IceCube-210629A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  63. Fermi-LAT Gamma-ray Observations of IceCube-210629A
  64. IceCube-210629A: Upper limits from Fermi-GBM Observations
  65. GRB 210627B: GECAM detection
  66. IceCube Alert 210629.76: Global MASTER-Net observations report
  67. GRB 210619B: Sayan observatory 1.6-m telescope observations
  68. IceCube-210629A - IceCube observation of a high-energy neutrino candidate track-like event
  69. GRB 210626A: Swift/XRT afterglow confirmation
  70. GRB 210626A: Fermi GBM observation
  71. GRB 210626A: CAHA 2.2m telescope optical limit
  72. GRB 210619B: Deep CAHA 2.2m detection and late-time light curve behavior
  73. GRB 210626A: Ondrejov D50 optical limit
  74. GRB 210626A: GIT optical upper limit
  75. Fermi trigger No 646443989: Global MASTER-Net observations report
  76. Fermi GRB 210627B: Global MASTER-Net observations report
  77. GRB 210627B: BALROG localization (Fermi Trigger 646509445/ GRB 210627748)
  78. GRB 210627B: Fermi GBM Final Real-time Localization
  79. Fermi GRB 210627A: Global MASTER-Net observations report
  80. GRB 210627A: Fermi GBM Final Real-time Localization
  81. GRB 210626A: Swift-XRT afterglow detection
  82. Fermi trigger No 646322348: Global MASTER-Net observations report
  83. Fermi GRB 210626A: Global MASTER-Net observations report
  84. GRB 210626A: Swift ToO observations
  85. GRB 210626A: Swift/BAT-GUANO detection and arcminute localization
  86. GRB 150428A: late-time radio observations
  87. GRB 210626A: Fermi GBM Final Real-time Localization
  88. GRB 210618A: 1.5m OSN optical upper limit
  89. Fermi GRB 210625A: Global MASTER-Net observations report
  90. GRB210619B: optical afterglow detection from Konkoly Observatory
  91. GRB 210625A: Fermi GBM Final Real-time Localization
  92. IPN triangulation of GRB 210624A (short)
  93. GRB 210622A: Swift-XRT observations
  94. GRB 210610B: T-CAT optical observations
  95. GRB 210619B: ASIM observation
  96. Fermi trigger No 646189108: Global MASTER-Net observations report
  97. Fermi GBM observation of a bright burst in the direction of SGR 1935+2154
  98. GRB 210618A: Swift-XRT afterglow detection
  99. Fermi trigger No 646194855: Global MASTER-Net observations report
  100. GRB 210622A: Swift ToO observations

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