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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 201209A: Enhanced Swift-XRT position
  2. IceCube-201130A: Optical and NIR Imaging Follow-up by Kanata Telescope
  3. GRB 201209A: KAIT Optical Upper Limit
  4. GRB 201209A: FRAM-Auger optical limit
  5. GRB 201209A: Swift detection of a burst
  6. Swift GRB201209.24: Global MASTER-Net observations report
  7. GRB 201208A: Fermi-LAT detection
  8. GRB 201208A: Swift ToO observations
  9. GRB 201208A: AstroSat CZTI detection
  10. GRB 201207A: AstroSat CZTI detection
  11. Fermi GRB 201208A: Global MASTER-Net observations report
  12. GRB 201208A: Fermi GBM Final Real-time Localization
  13. Fermi GRB 201207A: Global MASTER-Net observations report
  14. GRB 201207A: Fermi GBM Final Real-time Localization
  15. GRB 201203A: Swift-BAT refined analysis
  16. Swift follow-up observations of the flat spectrum radio quasar PMN J0206-1150 in the error region of IceCube-201130A
  17. GRB 201203A: GROWTH-India Telescope optical upper limit.
  18. GRB 201203A: MITSuME Okayama optical upper limits
  19. Swift GRB 201203A: Global MASTER-Net observations report
  20. GRB 201203A: Swift-XRT afterglow detection
  21. IceCube-201130A: No Candidate Counterparts from the Zwicky Transient Facility
  22. GRB 201203A: KAIT Optical Upper Limit
  23. GRB 201203A: DDOTI Observations
  24. GRB 201203A: FRAM-Auger optical limit
  25. GRB 201203A: Swift detection of a burst
  26. IceCube-201130A: No significant detection in HAWC
  27. IceCube-201130A: Upper limits from a search for additional neutrino events in IceCube
  28. IceCube-201130A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  29. GRB201130A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 628407054)
  30. GRB 201128B: Swift-XRT observations
  31. Swift observations of the Fermi-LAT source 4FGL J0206.4-1151 in the error region of IceCube-201130A
  32. Fermi-LAT Gamma-ray Observations of IceCube-201130A
  33. IceCube-201130A: Not observable by Fermi-GBM
  34. GRB 201201A: DDOTI Observations
  35. Fermi GRB 201201A: Global MASTER-Net observations report
  36. GRB 201128B: Swift ToO observations
  37. Swift-XRT observations of IceCube 201130A
  38. GRB 201201A: Fermi GBM Final Real-time Localization
  39. GRB 201128B: Swift/BAT-GUANO detection and arcminute localization
  40. GRB 201128A: Swift/UVOT Upper Limits
  41. IceCube-201130A: IceCube observation of a high-energy neutrino candidate event
  42. IceCube Alert 201130.85: Global MASTER-Net observations report
  43. GRB 201130A: DDOTI Observations
  44. Fermi GRB 201130A: Global MASTER-Net observations report
  45. GRB 201130A: Fermi GBM Final Real-time Localization
  46. Baksan Neutrino Observatory Alert 201128.90: Global MASTER-Net observations report
  47. GRB 201128A: Swift-BAT refined analysis
  48. GRB 201128A: Swift-XRT refined Analysis
  49. Fermi trigger No 628278856: Global MASTER-Net observations report
  50. GRB 201128A: Enhanced Swift-XRT position
  51. GRB 201128A: DDOTI Observations
  52. GRB 201128A: Swift detection of a burst
  53. Fermi trigger No 628140709: DDOTI/OAN optical observations report
  54. Fermi trigger No 628140709: Global MASTER-Net observations report
  55. IceCube-201114A: Updated photometry for three DECam candidate optical counterparts
  56. GRB 201121A: Insight-HXMT/HE detection
  57. AMON IC_HAWC NuEm-201124A: No Neutrino Counterpart detected with ANTARES
  58. IceCube-201120A in the Cygnus region: No enhanced TeV gamma-ray flux detected by HAWC
  59. IceCube Alert 201124.34: Global MASTER-Net observations report
  60. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-201124A
  61. GRB 200826A: TNG and LBT constraints on a supernova bump
  62. GRB 201122A: Insight-HXMT/HE detection
  63. IceCube-201114A: DECam observations and candidate optical counterpart
  64. IceCube-201120A: Upper limits from a search for additional neutrino events in IceCube
  65. GRB 201015A L-band observations with e-MERLIN
  66. INTEGRAL Weak #8831 and #8832: AROMA-N Optical Observation
  67. Fermi-LAT Gamma-ray Observations of IceCube-201120A
  68. IceCube-201120A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  69. Fermi trigger No 627645769: Global MASTER-Net observations report
  70. IceCube-201120A: Swift-XRT non-detection of 4FGL J2028.6+4110e
  71. GRB 201015A radio afterglow with e-MERLIN
  72. Fermi GRB 201121A: Global MASTER-Net observations report
  73. GRB 201121B: Fermi GBM Final Real-time Localization
  74. GRB 201121A: BALROG localization (Fermi Trigger 627614994 / GRB 201121062)
  75. GRB 201121A: Fermi GBM Final Real-time Localization
  76. Fermi GRB 201120B: Global MASTER-Net observations report
  77. GRB 201120B: Fermi GBM Final Localization
  78. GRB 201120A: Fermi GBM Final Localization
  79. IceCube-201120A: Upper limits from Fermi-GBM Observations
  80. Fermi trigger No 627557935: Global MASTER-Net observations report
  81. Baksan Neutrino Observatory Alert 201120.43: Global MASTER-Net observations report
  82. IceCube Alert 201120.41: Global MASTER-Net observations report
  83. IceCube-201120A: IceCube observation of a high-energy neutrino candidate event
  84. ZTF20acozryr/AT2020yxz (GRB 201103B): SAO RAS optical observations
  85. ZTF20acozryr/AT2020yxz (GRB 201103B): correction to the GCN #28883 CrAO/ZTSh optical observations
  86. IceCube 201114A: Swift followup of Fermi J0703.5+0505
  87. GRB 201116A: CALET Gamma-Ray Burst Monitor detection
  88. INTEGRAL Weak#8825: AROMA-N Optical Observation
  89. Fermi trigger No 627438255: Global MASTER-Net observations report
  90. Konus-Wind detection of GRB 201116A
  91. Trigger 1007266: Swift detection of 1A 0535+262
  92. Fermi-LAT Gamma-ray Observations of IceCube-201114A
  93. GRB 201116A: NOT optical observations
  94. GRB 201116A: Swift-XRT afterglow detection
  95. GRB 201116A: OSN Afterglow Candidate
  96. Swift Trigger 1006917 is Be/X-ray binary pulsar 1A 0535+262
  97. IceCube Alert 201115.67: Global MASTER-Net observations report
  98. Fermi trigger No 627198169: Global MASTER-Net observations report
  99. IceCube-201115A: Upper limits from a search for additional neutrino events in IceCube
  100. IceCube-201114A: Upper limits from a search for additional neutrino events in IceCube

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