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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. Fermi GRB 201208A: Global MASTER-Net observations report
  2. GRB 201208A: Fermi GBM Final Real-time Localization
  3. Fermi GRB 201207A: Global MASTER-Net observations report
  4. GRB 201207A: Fermi GBM Final Real-time Localization
  5. GRB 201203A: Swift-BAT refined analysis
  6. Swift follow-up observations of the flat spectrum radio quasar PMN J0206-1150 in the error region of IceCube-201130A
  7. GRB 201203A: GROWTH-India Telescope optical upper limit.
  8. GRB 201203A: MITSuME Okayama optical upper limits
  9. Swift GRB 201203A: Global MASTER-Net observations report
  10. GRB 201203A: Swift-XRT afterglow detection
  11. IceCube-201130A: No Candidate Counterparts from the Zwicky Transient Facility
  12. GRB 201203A: KAIT Optical Upper Limit
  13. GRB 201203A: DDOTI Observations
  14. GRB 201203A: FRAM-Auger optical limit
  15. GRB 201203A: Swift detection of a burst
  16. IceCube-201130A: No significant detection in HAWC
  17. IceCube-201130A: Upper limits from a search for additional neutrino events in IceCube
  18. IceCube-201130A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  19. GRB201130A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 628407054)
  20. GRB 201128B: Swift-XRT observations
  21. Swift observations of the Fermi-LAT source 4FGL J0206.4-1151 in the error region of IceCube-201130A
  22. Fermi-LAT Gamma-ray Observations of IceCube-201130A
  23. IceCube-201130A: Not observable by Fermi-GBM
  24. GRB 201201A: DDOTI Observations
  25. Fermi GRB 201201A: Global MASTER-Net observations report
  26. GRB 201128B: Swift ToO observations
  27. Swift-XRT observations of IceCube 201130A
  28. GRB 201201A: Fermi GBM Final Real-time Localization
  29. GRB 201128B: Swift/BAT-GUANO detection and arcminute localization
  30. GRB 201128A: Swift/UVOT Upper Limits
  31. IceCube-201130A: IceCube observation of a high-energy neutrino candidate event
  32. IceCube Alert 201130.85: Global MASTER-Net observations report
  33. GRB 201130A: DDOTI Observations
  34. Fermi GRB 201130A: Global MASTER-Net observations report
  35. GRB 201130A: Fermi GBM Final Real-time Localization
  36. Baksan Neutrino Observatory Alert 201128.90: Global MASTER-Net observations report
  37. GRB 201128A: Swift-BAT refined analysis
  38. GRB 201128A: Swift-XRT refined Analysis
  39. Fermi trigger No 628278856: Global MASTER-Net observations report
  40. GRB 201128A: Enhanced Swift-XRT position
  41. GRB 201128A: DDOTI Observations
  42. GRB 201128A: Swift detection of a burst
  43. Fermi trigger No 628140709: DDOTI/OAN optical observations report
  44. Fermi trigger No 628140709: Global MASTER-Net observations report
  45. IceCube-201114A: Updated photometry for three DECam candidate optical counterparts
  46. GRB 201121A: Insight-HXMT/HE detection
  47. AMON IC_HAWC NuEm-201124A: No Neutrino Counterpart detected with ANTARES
  48. IceCube-201120A in the Cygnus region: No enhanced TeV gamma-ray flux detected by HAWC
  49. IceCube Alert 201124.34: Global MASTER-Net observations report
  50. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-201124A
  51. GRB 200826A: TNG and LBT constraints on a supernova bump
  52. GRB 201122A: Insight-HXMT/HE detection
  53. IceCube-201114A: DECam observations and candidate optical counterpart
  54. IceCube-201120A: Upper limits from a search for additional neutrino events in IceCube
  55. GRB 201015A L-band observations with e-MERLIN
  56. INTEGRAL Weak #8831 and #8832: AROMA-N Optical Observation
  57. Fermi-LAT Gamma-ray Observations of IceCube-201120A
  58. IceCube-201120A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  59. Fermi trigger No 627645769: Global MASTER-Net observations report
  60. IceCube-201120A: Swift-XRT non-detection of 4FGL J2028.6+4110e
  61. GRB 201015A radio afterglow with e-MERLIN
  62. Fermi GRB 201121A: Global MASTER-Net observations report
  63. GRB 201121B: Fermi GBM Final Real-time Localization
  64. GRB 201121A: BALROG localization (Fermi Trigger 627614994 / GRB 201121062)
  65. GRB 201121A: Fermi GBM Final Real-time Localization
  66. Fermi GRB 201120B: Global MASTER-Net observations report
  67. GRB 201120B: Fermi GBM Final Localization
  68. GRB 201120A: Fermi GBM Final Localization
  69. IceCube-201120A: Upper limits from Fermi-GBM Observations
  70. Fermi trigger No 627557935: Global MASTER-Net observations report
  71. Baksan Neutrino Observatory Alert 201120.43: Global MASTER-Net observations report
  72. IceCube Alert 201120.41: Global MASTER-Net observations report
  73. IceCube-201120A: IceCube observation of a high-energy neutrino candidate event
  74. ZTF20acozryr/AT2020yxz (GRB 201103B): SAO RAS optical observations
  75. ZTF20acozryr/AT2020yxz (GRB 201103B): correction to the GCN #28883 CrAO/ZTSh optical observations
  76. IceCube 201114A: Swift followup of Fermi J0703.5+0505
  77. GRB 201116A: CALET Gamma-Ray Burst Monitor detection
  78. INTEGRAL Weak#8825: AROMA-N Optical Observation
  79. Fermi trigger No 627438255: Global MASTER-Net observations report
  80. Konus-Wind detection of GRB 201116A
  81. Trigger 1007266: Swift detection of 1A 0535+262
  82. Fermi-LAT Gamma-ray Observations of IceCube-201114A
  83. GRB 201116A: NOT optical observations
  84. GRB 201116A: Swift-XRT afterglow detection
  85. GRB 201116A: OSN Afterglow Candidate
  86. Swift Trigger 1006917 is Be/X-ray binary pulsar 1A 0535+262
  87. IceCube Alert 201115.67: Global MASTER-Net observations report
  88. Fermi trigger No 627198169: Global MASTER-Net observations report
  89. IceCube-201115A: Upper limits from a search for additional neutrino events in IceCube
  90. IceCube-201114A: Upper limits from a search for additional neutrino events in IceCube
  91. IceCube-201115A: No significant detection in HAWC
  92. IceCube-201114A: No significant detection in HAWC
  93. GRB 201116A: Fermi-LAT detection
  94. GRB 201116A: Tiled Swift observations
  95. LAT GRB201116.03: Global MASTER-Net observations report
  96. IceCube-201115A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  97. IceCube-201114A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  98. INTEGRAL Weak#8811: AROMA-N Optical Observation
  99. IceCube-201115A: No neutrino counterpart candidates in ANTARES search
  100. IceCube Alert 201115.09: Global MASTER-Net observations report

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