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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. Fermi GBM Sub-Threshold Detection of GRB 201221A
  2. GRB 201221A: Swift/UVOT Upper Limits
  3. GRB 201221A: Swift-XRT refined Analysis
  4. GRB 201221C: MASTER optical observtion
  5. Swift Trigger 1014012: possible GRB 201221C
  6. GRB 201221A: Enhanced Swift-XRT position
  7. IceCube-201221A: not observable by Fermi-GBM
  8. IceCube-201221A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  9. IceCube-201221A: IceCube observation of a high-energy neutrino candidate event
  10. GRB 201221B: Fermi GBM Final Real-time Localization
  11. GRB 201221A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 5.7
  12. GRB 201221A: FRAM-Auger optical limit
  13. Swift GRB 201221A: Global MASTER-Net observations report
  14. GRB 201221A: Prompt enhanced Swift-XRT position
  15. GRB 201221A: Swift detection of a burst
  16. Konus-Wind observation of GRB 201218A
  17. GRB 201209A: Mondy optical observations, afterglow confirmation
  18. GRB 201214A: TSHAO optical upper limit
  19. GRB 201214A: Swift-XRT afterglow detection
  20. GRB 201214A: 1.3m DFOT, optical upper limits
  21. IPN triangulation of GRB 201218A
  22. Fermi GRB 201218B: Global MASTER-Net observations report
  23. GRB 201218B: Fermi GBM Final Real-time Localization
  24. Fermi GRB 201218A: Global MASTER-Net observations report
  25. GRB201216C: No significant detection in HAWC
  26. GRB 201216C: Liverpool Telescope First Hour Observations
  27. Konus-Wind detection of GRB 201216C
  28. GRB 201218A: BALROG localization (Fermi Trigger 629957660 / GRB 201218177)
  29. IceCube-201209A : MAXI/GSC upper limit
  30. GRB 201218A: Fermi GBM Final Real-time Localization
  31. GRB 201216C: Swift-BAT refined analysis
  32. Fermi GRB 201217A: Global MASTER-Net observations report
  33. GRB 201217A: Fermi GBM Final Localization
  34. GRB 201216C: VLT X-shooter spectroscopy and potential high redshift of a VHE-emitting GRB
  35. GRB 201216C: Fermi-LAT upper limit
  36. GRB 201216C: MAGIC detection in very high energy gamma rays
  37. GRB 201216C: AstroSat CZTI detection
  38. GRB 201216C: Fermi GBM detection
  39. GRB 201216A: Fermi GBM detection
  40. GRB 201216C: Swift/UVOT Upper Limits
  41. GRB 201216C: FRAM-ORM afterglow confirmation
  42. GRB 201216A: Swift-XRT observations
  43. Baksan Neutrino Observatory Alert 201216.94: Global MASTER-Net observations report
  44. GRB 201216C: Enhanced Swift-XRT position
  45. GRB 201216C: VLT afterglow candidate discovery
  46. GRB 201216A: Swift ToO observations
  47. GRB 201216C: Swift-XRT observations
  48. GRB 201216C: Fermi GBM Final Real-time Localization
  49. Swift GRB201216.96: Global MASTER-Net observations report
  50. GRB 201216C: Swift detection of a burst
  51. Fermi GRB 201216A: Global MASTER-Net observations report
  52. GRB 201216A: Swift/BAT-GUANO detection and arcminute localization
  53. GRB 201216B: AGILE detection of a burst
  54. GRB 201216A: Fermi GBM Final Real-time Localization
  55. GRB 201214B: MITSuME Akeno optical upper limits
  56. Chandra observations of GW170817 at ~3.3 years since merger (Full report)
  57. GRB 201214B: Lowell Discovery Telescope optical observations
  58. VLA observations of GW170817 at ~3.3 years post-merger
  59. GRB 201214B: Swift-XRT observations
  60. Fermi GRB 201215A: Global MASTER-Net observations report
  61. GRB 201209A: Insight-HXMT/HE detection
  62. IceCube-201209A: Upper limits from Insight-HXMT/HE observations
  63. GRB 201214A: Swift-XRT observations
  64. GRB 201215A: BALROG localization (Fermi Trigger 629706213 / GRB 201215266)
  65. GRB 201215A: Fermi GBM Final Real-time Localization
  66. GRB 201214B: Swift BAT location of short burst
  67. Fermi GRB 201214B: Global MASTER-Net observations report
  68. GRB 201214B: Swift ToO observations
  69. IceCube-201209: No significant detection in HAWC
  70. Potential X-ray KN afterglow from Chandra observations of GW170817 ~3.3 years since merger (3 Epochs of 4)
  71. GRB 201214A: Mates' birthday GRB optical limit from FRAM-ORM
  72. GRB 201214B: Fermi GBM Final Real-time Localization
  73. Long-lasting X-ray emission from GW170817 detected by Chandra
  74. GRB 201214A: A long GRB detected by INTEGRAL
  75. GRB 201214A: Swift ToO observations
  76. Integral GRB201214.26: Global MASTER-Net observations report
  77. GRB 201213A: Fermi GBM Final Real-time Localization
  78. GRB 201015A: optical observations and supernova identification
  79. GRB 201203A: Zeiss-1000 (Koshka observatory) optical upper limit
  80. IceCube-201209A: No Candidate Counterparts from the Zwicky Transient Facility
  81. GRB 201203A: 1.3m DFOT, optical upper limits
  82. GRB 200826A: GMOS-N detected source magnitude (Correction)
  83. GRB 201015A: 5-GHz radio afterglow detection with the EVN
  84. IceCube-201209A: Upper limits from a search for additional neutrino events in IceCube
  85. GRB 201209A: Swift/UVOT Upper Limits
  86. IceCube-201209A: Upper limits from Fermi-GBM Observations
  87. Fermi-LAT Gamma-ray Observations of IceCube-201209A
  88. IceCube-201209A: No neutrino counterpart candidates in ANTARES search
  89. IceCube Alert 201209.43: Global MASTER-Net observations report
  90. GRB 201209A: Swift-BAT refined analysis
  91. IPN triangulation of GRB 201207A
  92. Chandra observations of GW170817 at ~3.3 years since merger (Observation 1 of 4)
  93. GRB 201208A: Swift-XRT afterglow detection
  94. GRB 201208A: Fermi GBM observation
  95. IceCube-201209A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  96. GRB 201208A: LCO observations
  97. GRB 201209A: Swift-XRT refined Analysis
  98. GRB 201209A: Xinglong-2.16m likely optical afterglow detection
  99. IceCube-201209A: IceCube observation of a high-energy neutrino candidate event
  100. GRB 201209A: AstroSat CZTI detection

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