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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 201208A: Swift ToO observations
  2. GRB 201208A: AstroSat CZTI detection
  3. GRB 201207A: AstroSat CZTI detection
  4. Fermi GRB 201208A: Global MASTER-Net observations report
  5. GRB 201208A: Fermi GBM Final Real-time Localization
  6. Fermi GRB 201207A: Global MASTER-Net observations report
  7. GRB 201207A: Fermi GBM Final Real-time Localization
  8. GRB 201203A: Swift-BAT refined analysis
  9. Swift follow-up observations of the flat spectrum radio quasar PMN J0206-1150 in the error region of IceCube-201130A
  10. GRB 201203A: GROWTH-India Telescope optical upper limit.
  11. GRB 201203A: MITSuME Okayama optical upper limits
  12. Swift GRB 201203A: Global MASTER-Net observations report
  13. GRB 201203A: Swift-XRT afterglow detection
  14. IceCube-201130A: No Candidate Counterparts from the Zwicky Transient Facility
  15. GRB 201203A: KAIT Optical Upper Limit
  16. GRB 201203A: DDOTI Observations
  17. GRB 201203A: FRAM-Auger optical limit
  18. GRB 201203A: Swift detection of a burst
  19. IceCube-201130A: No significant detection in HAWC
  20. IceCube-201130A: Upper limits from a search for additional neutrino events in IceCube
  21. IceCube-201130A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  22. GRB201130A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 628407054)
  23. GRB 201128B: Swift-XRT observations
  24. Swift observations of the Fermi-LAT source 4FGL J0206.4-1151 in the error region of IceCube-201130A
  25. Fermi-LAT Gamma-ray Observations of IceCube-201130A
  26. IceCube-201130A: Not observable by Fermi-GBM
  27. GRB 201201A: DDOTI Observations
  28. Fermi GRB 201201A: Global MASTER-Net observations report
  29. GRB 201128B: Swift ToO observations
  30. Swift-XRT observations of IceCube 201130A
  31. GRB 201201A: Fermi GBM Final Real-time Localization
  32. GRB 201128B: Swift/BAT-GUANO detection and arcminute localization
  33. GRB 201128A: Swift/UVOT Upper Limits
  34. IceCube-201130A: IceCube observation of a high-energy neutrino candidate event
  35. IceCube Alert 201130.85: Global MASTER-Net observations report
  36. GRB 201130A: DDOTI Observations
  37. Fermi GRB 201130A: Global MASTER-Net observations report
  38. GRB 201130A: Fermi GBM Final Real-time Localization
  39. Baksan Neutrino Observatory Alert 201128.90: Global MASTER-Net observations report
  40. GRB 201128A: Swift-BAT refined analysis
  41. GRB 201128A: Swift-XRT refined Analysis
  42. Fermi trigger No 628278856: Global MASTER-Net observations report
  43. GRB 201128A: Enhanced Swift-XRT position
  44. GRB 201128A: DDOTI Observations
  45. GRB 201128A: Swift detection of a burst
  46. Fermi trigger No 628140709: DDOTI/OAN optical observations report
  47. Fermi trigger No 628140709: Global MASTER-Net observations report
  48. IceCube-201114A: Updated photometry for three DECam candidate optical counterparts
  49. GRB 201121A: Insight-HXMT/HE detection
  50. AMON IC_HAWC NuEm-201124A: No Neutrino Counterpart detected with ANTARES
  51. IceCube-201120A in the Cygnus region: No enhanced TeV gamma-ray flux detected by HAWC
  52. IceCube Alert 201124.34: Global MASTER-Net observations report
  53. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-201124A
  54. GRB 200826A: TNG and LBT constraints on a supernova bump
  55. GRB 201122A: Insight-HXMT/HE detection
  56. IceCube-201114A: DECam observations and candidate optical counterpart
  57. IceCube-201120A: Upper limits from a search for additional neutrino events in IceCube
  58. GRB 201015A L-band observations with e-MERLIN
  59. INTEGRAL Weak #8831 and #8832: AROMA-N Optical Observation
  60. Fermi-LAT Gamma-ray Observations of IceCube-201120A
  61. IceCube-201120A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  62. Fermi trigger No 627645769: Global MASTER-Net observations report
  63. IceCube-201120A: Swift-XRT non-detection of 4FGL J2028.6+4110e
  64. GRB 201015A radio afterglow with e-MERLIN
  65. Fermi GRB 201121A: Global MASTER-Net observations report
  66. GRB 201121B: Fermi GBM Final Real-time Localization
  67. GRB 201121A: BALROG localization (Fermi Trigger 627614994 / GRB 201121062)
  68. GRB 201121A: Fermi GBM Final Real-time Localization
  69. Fermi GRB 201120B: Global MASTER-Net observations report
  70. GRB 201120B: Fermi GBM Final Localization
  71. GRB 201120A: Fermi GBM Final Localization
  72. IceCube-201120A: Upper limits from Fermi-GBM Observations
  73. Fermi trigger No 627557935: Global MASTER-Net observations report
  74. Baksan Neutrino Observatory Alert 201120.43: Global MASTER-Net observations report
  75. IceCube Alert 201120.41: Global MASTER-Net observations report
  76. IceCube-201120A: IceCube observation of a high-energy neutrino candidate event
  77. ZTF20acozryr/AT2020yxz (GRB 201103B): SAO RAS optical observations
  78. ZTF20acozryr/AT2020yxz (GRB 201103B): correction to the GCN #28883 CrAO/ZTSh optical observations
  79. IceCube 201114A: Swift followup of Fermi J0703.5+0505
  80. GRB 201116A: CALET Gamma-Ray Burst Monitor detection
  81. INTEGRAL Weak#8825: AROMA-N Optical Observation
  82. Fermi trigger No 627438255: Global MASTER-Net observations report
  83. Konus-Wind detection of GRB 201116A
  84. Trigger 1007266: Swift detection of 1A 0535+262
  85. Fermi-LAT Gamma-ray Observations of IceCube-201114A
  86. GRB 201116A: NOT optical observations
  87. GRB 201116A: Swift-XRT afterglow detection
  88. GRB 201116A: OSN Afterglow Candidate
  89. Swift Trigger 1006917 is Be/X-ray binary pulsar 1A 0535+262
  90. IceCube Alert 201115.67: Global MASTER-Net observations report
  91. Fermi trigger No 627198169: Global MASTER-Net observations report
  92. IceCube-201115A: Upper limits from a search for additional neutrino events in IceCube
  93. IceCube-201114A: Upper limits from a search for additional neutrino events in IceCube
  94. IceCube-201115A: No significant detection in HAWC
  95. IceCube-201114A: No significant detection in HAWC
  96. GRB 201116A: Fermi-LAT detection
  97. GRB 201116A: Tiled Swift observations
  98. LAT GRB201116.03: Global MASTER-Net observations report
  99. IceCube-201115A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  100. IceCube-201114A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation

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