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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 201222A: Fermi GBM Final Real-time Localization
  2. GRB 201221E: Fermi GBM Final Real-time Localization
  3. GRB 201221D: Prompt enhanced Swift-XRT position
  4. GRB 201221D: Swift detection of a bright short burst
  5. correction to GCN 29110 - Fermi GBM Sub-Threshold Detection of GRB 201221A
  6. Fermi GBM Sub-Threshold Detection of GRB 201221A
  7. GRB 201221A: Swift/UVOT Upper Limits
  8. GRB 201221A: Swift-XRT refined Analysis
  9. GRB 201221C: MASTER optical observtion
  10. Swift Trigger 1014012: possible GRB 201221C
  11. GRB 201221A: Enhanced Swift-XRT position
  12. IceCube-201221A: not observable by Fermi-GBM
  13. IceCube-201221A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  14. IceCube-201221A: IceCube observation of a high-energy neutrino candidate event
  15. GRB 201221B: Fermi GBM Final Real-time Localization
  16. GRB 201221A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 5.7
  17. GRB 201221A: FRAM-Auger optical limit
  18. Swift GRB 201221A: Global MASTER-Net observations report
  19. GRB 201221A: Prompt enhanced Swift-XRT position
  20. GRB 201221A: Swift detection of a burst
  21. Konus-Wind observation of GRB 201218A
  22. GRB 201209A: Mondy optical observations, afterglow confirmation
  23. GRB 201214A: TSHAO optical upper limit
  24. GRB 201214A: Swift-XRT afterglow detection
  25. GRB 201214A: 1.3m DFOT, optical upper limits
  26. IPN triangulation of GRB 201218A
  27. Fermi GRB 201218B: Global MASTER-Net observations report
  28. GRB 201218B: Fermi GBM Final Real-time Localization
  29. Fermi GRB 201218A: Global MASTER-Net observations report
  30. GRB201216C: No significant detection in HAWC
  31. GRB 201216C: Liverpool Telescope First Hour Observations
  32. Konus-Wind detection of GRB 201216C
  33. GRB 201218A: BALROG localization (Fermi Trigger 629957660 / GRB 201218177)
  34. IceCube-201209A : MAXI/GSC upper limit
  35. GRB 201218A: Fermi GBM Final Real-time Localization
  36. GRB 201216C: Swift-BAT refined analysis
  37. Fermi GRB 201217A: Global MASTER-Net observations report
  38. GRB 201217A: Fermi GBM Final Localization
  39. GRB 201216C: VLT X-shooter spectroscopy and potential high redshift of a VHE-emitting GRB
  40. GRB 201216C: Fermi-LAT upper limit
  41. GRB 201216C: MAGIC detection in very high energy gamma rays
  42. GRB 201216C: AstroSat CZTI detection
  43. GRB 201216C: Fermi GBM detection
  44. GRB 201216A: Fermi GBM detection
  45. GRB 201216C: Swift/UVOT Upper Limits
  46. GRB 201216C: FRAM-ORM afterglow confirmation
  47. GRB 201216A: Swift-XRT observations
  48. Baksan Neutrino Observatory Alert 201216.94: Global MASTER-Net observations report
  49. GRB 201216C: Enhanced Swift-XRT position
  50. GRB 201216C: VLT afterglow candidate discovery
  51. GRB 201216A: Swift ToO observations
  52. GRB 201216C: Swift-XRT observations
  53. GRB 201216C: Fermi GBM Final Real-time Localization
  54. Swift GRB201216.96: Global MASTER-Net observations report
  55. GRB 201216C: Swift detection of a burst
  56. Fermi GRB 201216A: Global MASTER-Net observations report
  57. GRB 201216A: Swift/BAT-GUANO detection and arcminute localization
  58. GRB 201216B: AGILE detection of a burst
  59. GRB 201216A: Fermi GBM Final Real-time Localization
  60. GRB 201214B: MITSuME Akeno optical upper limits
  61. Chandra observations of GW170817 at ~3.3 years since merger (Full report)
  62. GRB 201214B: Lowell Discovery Telescope optical observations
  63. VLA observations of GW170817 at ~3.3 years post-merger
  64. GRB 201214B: Swift-XRT observations
  65. Fermi GRB 201215A: Global MASTER-Net observations report
  66. GRB 201209A: Insight-HXMT/HE detection
  67. IceCube-201209A: Upper limits from Insight-HXMT/HE observations
  68. GRB 201214A: Swift-XRT observations
  69. GRB 201215A: BALROG localization (Fermi Trigger 629706213 / GRB 201215266)
  70. GRB 201215A: Fermi GBM Final Real-time Localization
  71. GRB 201214B: Swift BAT location of short burst
  72. Fermi GRB 201214B: Global MASTER-Net observations report
  73. GRB 201214B: Swift ToO observations
  74. IceCube-201209: No significant detection in HAWC
  75. Potential X-ray KN afterglow from Chandra observations of GW170817 ~3.3 years since merger (3 Epochs of 4)
  76. GRB 201214A: Mates' birthday GRB optical limit from FRAM-ORM
  77. GRB 201214B: Fermi GBM Final Real-time Localization
  78. Long-lasting X-ray emission from GW170817 detected by Chandra
  79. GRB 201214A: A long GRB detected by INTEGRAL
  80. GRB 201214A: Swift ToO observations
  81. Integral GRB201214.26: Global MASTER-Net observations report
  82. GRB 201213A: Fermi GBM Final Real-time Localization
  83. GRB 201015A: optical observations and supernova identification
  84. GRB 201203A: Zeiss-1000 (Koshka observatory) optical upper limit
  85. IceCube-201209A: No Candidate Counterparts from the Zwicky Transient Facility
  86. GRB 201203A: 1.3m DFOT, optical upper limits
  87. GRB 200826A: GMOS-N detected source magnitude (Correction)
  88. GRB 201015A: 5-GHz radio afterglow detection with the EVN
  89. IceCube-201209A: Upper limits from a search for additional neutrino events in IceCube
  90. GRB 201209A: Swift/UVOT Upper Limits
  91. IceCube-201209A: Upper limits from Fermi-GBM Observations
  92. Fermi-LAT Gamma-ray Observations of IceCube-201209A
  93. IceCube-201209A: No neutrino counterpart candidates in ANTARES search
  94. IceCube Alert 201209.43: Global MASTER-Net observations report
  95. GRB 201209A: Swift-BAT refined analysis
  96. IPN triangulation of GRB 201207A
  97. Chandra observations of GW170817 at ~3.3 years since merger (Observation 1 of 4)
  98. GRB 201208A: Swift-XRT afterglow detection
  99. GRB 201208A: Fermi GBM observation
  100. IceCube-201209A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation

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