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

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