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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 201214A: TSHAO optical upper limit
  2. GRB 201214A: Swift-XRT afterglow detection
  3. GRB 201214A: 1.3m DFOT, optical upper limits
  4. IPN triangulation of GRB 201218A
  5. Fermi GRB 201218B: Global MASTER-Net observations report
  6. GRB 201218B: Fermi GBM Final Real-time Localization
  7. Fermi GRB 201218A: Global MASTER-Net observations report
  8. GRB201216C: No significant detection in HAWC
  9. GRB 201216C: Liverpool Telescope First Hour Observations
  10. Konus-Wind detection of GRB 201216C
  11. GRB 201218A: BALROG localization (Fermi Trigger 629957660 / GRB 201218177)
  12. IceCube-201209A : MAXI/GSC upper limit
  13. GRB 201218A: Fermi GBM Final Real-time Localization
  14. GRB 201216C: Swift-BAT refined analysis
  15. Fermi GRB 201217A: Global MASTER-Net observations report
  16. GRB 201217A: Fermi GBM Final Localization
  17. GRB 201216C: VLT X-shooter spectroscopy and potential high redshift of a VHE-emitting GRB
  18. GRB 201216C: Fermi-LAT upper limit
  19. GRB 201216C: MAGIC detection in very high energy gamma rays
  20. GRB 201216C: AstroSat CZTI detection
  21. GRB 201216C: Fermi GBM detection
  22. GRB 201216A: Fermi GBM detection
  23. GRB 201216C: Swift/UVOT Upper Limits
  24. GRB 201216C: FRAM-ORM afterglow confirmation
  25. GRB 201216A: Swift-XRT observations
  26. Baksan Neutrino Observatory Alert 201216.94: Global MASTER-Net observations report
  27. GRB 201216C: Enhanced Swift-XRT position
  28. GRB 201216C: VLT afterglow candidate discovery
  29. GRB 201216A: Swift ToO observations
  30. GRB 201216C: Swift-XRT observations
  31. GRB 201216C: Fermi GBM Final Real-time Localization
  32. Swift GRB201216.96: Global MASTER-Net observations report
  33. GRB 201216C: Swift detection of a burst
  34. Fermi GRB 201216A: Global MASTER-Net observations report
  35. GRB 201216A: Swift/BAT-GUANO detection and arcminute localization
  36. GRB 201216B: AGILE detection of a burst
  37. GRB 201216A: Fermi GBM Final Real-time Localization
  38. GRB 201214B: MITSuME Akeno optical upper limits
  39. Chandra observations of GW170817 at ~3.3 years since merger (Full report)
  40. GRB 201214B: Lowell Discovery Telescope optical observations
  41. VLA observations of GW170817 at ~3.3 years post-merger
  42. GRB 201214B: Swift-XRT observations
  43. Fermi GRB 201215A: Global MASTER-Net observations report
  44. GRB 201209A: Insight-HXMT/HE detection
  45. IceCube-201209A: Upper limits from Insight-HXMT/HE observations
  46. GRB 201214A: Swift-XRT observations
  47. GRB 201215A: BALROG localization (Fermi Trigger 629706213 / GRB 201215266)
  48. GRB 201215A: Fermi GBM Final Real-time Localization
  49. GRB 201214B: Swift BAT location of short burst
  50. Fermi GRB 201214B: Global MASTER-Net observations report
  51. GRB 201214B: Swift ToO observations
  52. IceCube-201209: No significant detection in HAWC
  53. Potential X-ray KN afterglow from Chandra observations of GW170817 ~3.3 years since merger (3 Epochs of 4)
  54. GRB 201214A: Mates' birthday GRB optical limit from FRAM-ORM
  55. GRB 201214B: Fermi GBM Final Real-time Localization
  56. Long-lasting X-ray emission from GW170817 detected by Chandra
  57. GRB 201214A: A long GRB detected by INTEGRAL
  58. GRB 201214A: Swift ToO observations
  59. Integral GRB201214.26: Global MASTER-Net observations report
  60. GRB 201213A: Fermi GBM Final Real-time Localization
  61. GRB 201015A: optical observations and supernova identification
  62. GRB 201203A: Zeiss-1000 (Koshka observatory) optical upper limit
  63. IceCube-201209A: No Candidate Counterparts from the Zwicky Transient Facility
  64. GRB 201203A: 1.3m DFOT, optical upper limits
  65. GRB 200826A: GMOS-N detected source magnitude (Correction)
  66. GRB 201015A: 5-GHz radio afterglow detection with the EVN
  67. IceCube-201209A: Upper limits from a search for additional neutrino events in IceCube
  68. GRB 201209A: Swift/UVOT Upper Limits
  69. IceCube-201209A: Upper limits from Fermi-GBM Observations
  70. Fermi-LAT Gamma-ray Observations of IceCube-201209A
  71. IceCube-201209A: No neutrino counterpart candidates in ANTARES search
  72. IceCube Alert 201209.43: Global MASTER-Net observations report
  73. GRB 201209A: Swift-BAT refined analysis
  74. IPN triangulation of GRB 201207A
  75. Chandra observations of GW170817 at ~3.3 years since merger (Observation 1 of 4)
  76. GRB 201208A: Swift-XRT afterglow detection
  77. GRB 201208A: Fermi GBM observation
  78. IceCube-201209A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  79. GRB 201208A: LCO observations
  80. GRB 201209A: Swift-XRT refined Analysis
  81. GRB 201209A: Xinglong-2.16m likely optical afterglow detection
  82. IceCube-201209A: IceCube observation of a high-energy neutrino candidate event
  83. GRB 201209A: AstroSat CZTI detection
  84. GRB 201207A: AGILE detection
  85. GRB 201209A: Enhanced Swift-XRT position
  86. IceCube-201130A: Optical and NIR Imaging Follow-up by Kanata Telescope
  87. GRB 201209A: KAIT Optical Upper Limit
  88. GRB 201209A: FRAM-Auger optical limit
  89. GRB 201209A: Swift detection of a burst
  90. Swift GRB201209.24: Global MASTER-Net observations report
  91. GRB 201208A: Fermi-LAT detection
  92. GRB 201208A: Swift ToO observations
  93. GRB 201208A: AstroSat CZTI detection
  94. GRB 201207A: AstroSat CZTI detection
  95. Fermi GRB 201208A: Global MASTER-Net observations report
  96. GRB 201208A: Fermi GBM Final Real-time Localization
  97. Fermi GRB 201207A: Global MASTER-Net observations report
  98. GRB 201207A: Fermi GBM Final Real-time Localization
  99. GRB 201203A: Swift-BAT refined analysis
  100. Swift follow-up observations of the flat spectrum radio quasar PMN J0206-1150 in the error region of IceCube-201130A

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