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

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