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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 201221D: Swift-BAT refined analysis
  2. Swift Trigger 1014012 (possible GRB 201221C) is likely not an astrophysical event
  3. GRB 201216A - further Swift-XRT observations
  4. Fermi-LAT Gamma-ray Observations of IceCube-201222A
  5. Fermi-LAT Gamma-ray Observations of IceCube-201221A
  6. IceCube-201222A: not observable by Fermi-GBM
  7. GRB 201221D: Archival PS1 Imaging of the Putative Host Galaxy
  8. Short GRB201221D: High Redshift from OSIRIS/GTC
  9. IceCube-201222A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  10. Konus-Wind detection of GRB 201221D (short)
  11. GRB 201221D: Swift/UVOT Upper Limits
  12. GRB 201221D: Lowell Discovery Telescope afterglow observations
  13. GRB 201222B: BALROG localization (Fermi Trigger / GRB 201222461)
  14. GRB 201222B: Fermi GBM Final Real-time Localization
  15. GRB 201221D: FRAM-ORM optical limit
  16. GRB 201221D: Swift-XRT refined Analysis
  17. IceCube Alert 201222.04: Global MASTER-Net observations report
  18. Swift GRB 201221D: Global MASTER-Net observations report
  19. Fermi GRB 201221E: Global MASTER-Net observations report
  20. IceCube-201222A: IceCube observation of a high-energy neutrino candidate event
  21. GRB 201221D: Enhanced Swift-XRT position
  22. GRB 201221D: Nanshan/NEXT early optical upper limit
  23. GRB 201221D: candidate optical counterpart from the NOT
  24. GRB 201221A: Swift-BAT refined analysis
  25. GRB 201222A: Fermi GBM Final Real-time Localization
  26. GRB 201221E: Fermi GBM Final Real-time Localization
  27. GRB 201221D: Prompt enhanced Swift-XRT position
  28. GRB 201221D: Swift detection of a bright short burst
  29. correction to GCN 29110 - Fermi GBM Sub-Threshold Detection of GRB 201221A
  30. Fermi GBM Sub-Threshold Detection of GRB 201221A
  31. GRB 201221A: Swift/UVOT Upper Limits
  32. GRB 201221A: Swift-XRT refined Analysis
  33. GRB 201221C: MASTER optical observtion
  34. Swift Trigger 1014012: possible GRB 201221C
  35. GRB 201221A: Enhanced Swift-XRT position
  36. IceCube-201221A: not observable by Fermi-GBM
  37. IceCube-201221A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  38. IceCube-201221A: IceCube observation of a high-energy neutrino candidate event
  39. GRB 201221B: Fermi GBM Final Real-time Localization
  40. GRB 201221A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 5.7
  41. GRB 201221A: FRAM-Auger optical limit
  42. Swift GRB 201221A: Global MASTER-Net observations report
  43. GRB 201221A: Prompt enhanced Swift-XRT position
  44. GRB 201221A: Swift detection of a burst
  45. Konus-Wind observation of GRB 201218A
  46. GRB 201209A: Mondy optical observations, afterglow confirmation
  47. GRB 201214A: TSHAO optical upper limit
  48. GRB 201214A: Swift-XRT afterglow detection
  49. GRB 201214A: 1.3m DFOT, optical upper limits
  50. IPN triangulation of GRB 201218A
  51. Fermi GRB 201218B: Global MASTER-Net observations report
  52. GRB 201218B: Fermi GBM Final Real-time Localization
  53. Fermi GRB 201218A: Global MASTER-Net observations report
  54. GRB201216C: No significant detection in HAWC
  55. GRB 201216C: Liverpool Telescope First Hour Observations
  56. Konus-Wind detection of GRB 201216C
  57. GRB 201218A: BALROG localization (Fermi Trigger 629957660 / GRB 201218177)
  58. IceCube-201209A : MAXI/GSC upper limit
  59. GRB 201218A: Fermi GBM Final Real-time Localization
  60. GRB 201216C: Swift-BAT refined analysis
  61. Fermi GRB 201217A: Global MASTER-Net observations report
  62. GRB 201217A: Fermi GBM Final Localization
  63. GRB 201216C: VLT X-shooter spectroscopy and potential high redshift of a VHE-emitting GRB
  64. GRB 201216C: Fermi-LAT upper limit
  65. GRB 201216C: MAGIC detection in very high energy gamma rays
  66. GRB 201216C: AstroSat CZTI detection
  67. GRB 201216C: Fermi GBM detection
  68. GRB 201216A: Fermi GBM detection
  69. GRB 201216C: Swift/UVOT Upper Limits
  70. GRB 201216C: FRAM-ORM afterglow confirmation
  71. GRB 201216A: Swift-XRT observations
  72. Baksan Neutrino Observatory Alert 201216.94: Global MASTER-Net observations report
  73. GRB 201216C: Enhanced Swift-XRT position
  74. GRB 201216C: VLT afterglow candidate discovery
  75. GRB 201216A: Swift ToO observations
  76. GRB 201216C: Swift-XRT observations
  77. GRB 201216C: Fermi GBM Final Real-time Localization
  78. Swift GRB201216.96: Global MASTER-Net observations report
  79. GRB 201216C: Swift detection of a burst
  80. Fermi GRB 201216A: Global MASTER-Net observations report
  81. GRB 201216A: Swift/BAT-GUANO detection and arcminute localization
  82. GRB 201216B: AGILE detection of a burst
  83. GRB 201216A: Fermi GBM Final Real-time Localization
  84. GRB 201214B: MITSuME Akeno optical upper limits
  85. Chandra observations of GW170817 at ~3.3 years since merger (Full report)
  86. GRB 201214B: Lowell Discovery Telescope optical observations
  87. VLA observations of GW170817 at ~3.3 years post-merger
  88. GRB 201214B: Swift-XRT observations
  89. Fermi GRB 201215A: Global MASTER-Net observations report
  90. GRB 201209A: Insight-HXMT/HE detection
  91. IceCube-201209A: Upper limits from Insight-HXMT/HE observations
  92. GRB 201214A: Swift-XRT observations
  93. GRB 201215A: BALROG localization (Fermi Trigger 629706213 / GRB 201215266)
  94. GRB 201215A: Fermi GBM Final Real-time Localization
  95. GRB 201214B: Swift BAT location of short burst
  96. Fermi GRB 201214B: Global MASTER-Net observations report
  97. GRB 201214B: Swift ToO observations
  98. IceCube-201209: No significant detection in HAWC
  99. Potential X-ray KN afterglow from Chandra observations of GW170817 ~3.3 years since merger (3 Epochs of 4)
  100. GRB 201214A: Mates' birthday GRB optical limit from FRAM-ORM

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