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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 201203A: GROWTH-India Telescope optical upper limit.
  2. GRB 201203A: MITSuME Okayama optical upper limits
  3. Swift GRB 201203A: Global MASTER-Net observations report
  4. GRB 201203A: Swift-XRT afterglow detection
  5. IceCube-201130A: No Candidate Counterparts from the Zwicky Transient Facility
  6. GRB 201203A: KAIT Optical Upper Limit
  7. GRB 201203A: DDOTI Observations
  8. GRB 201203A: FRAM-Auger optical limit
  9. GRB 201203A: Swift detection of a burst
  10. IceCube-201130A: No significant detection in HAWC
  11. IceCube-201130A: Upper limits from a search for additional neutrino events in IceCube
  12. IceCube-201130A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  13. GRB201130A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 628407054)
  14. GRB 201128B: Swift-XRT observations
  15. Swift observations of the Fermi-LAT source 4FGL J0206.4-1151 in the error region of IceCube-201130A
  16. Fermi-LAT Gamma-ray Observations of IceCube-201130A
  17. IceCube-201130A: Not observable by Fermi-GBM
  18. GRB 201201A: DDOTI Observations
  19. Fermi GRB 201201A: Global MASTER-Net observations report
  20. GRB 201128B: Swift ToO observations
  21. Swift-XRT observations of IceCube 201130A
  22. GRB 201201A: Fermi GBM Final Real-time Localization
  23. GRB 201128B: Swift/BAT-GUANO detection and arcminute localization
  24. GRB 201128A: Swift/UVOT Upper Limits
  25. IceCube-201130A: IceCube observation of a high-energy neutrino candidate event
  26. IceCube Alert 201130.85: Global MASTER-Net observations report
  27. GRB 201130A: DDOTI Observations
  28. Fermi GRB 201130A: Global MASTER-Net observations report
  29. GRB 201130A: Fermi GBM Final Real-time Localization
  30. Baksan Neutrino Observatory Alert 201128.90: Global MASTER-Net observations report
  31. GRB 201128A: Swift-BAT refined analysis
  32. GRB 201128A: Swift-XRT refined Analysis
  33. Fermi trigger No 628278856: Global MASTER-Net observations report
  34. GRB 201128A: Enhanced Swift-XRT position
  35. GRB 201128A: DDOTI Observations
  36. GRB 201128A: Swift detection of a burst
  37. Fermi trigger No 628140709: DDOTI/OAN optical observations report
  38. Fermi trigger No 628140709: Global MASTER-Net observations report
  39. IceCube-201114A: Updated photometry for three DECam candidate optical counterparts
  40. GRB 201121A: Insight-HXMT/HE detection
  41. AMON IC_HAWC NuEm-201124A: No Neutrino Counterpart detected with ANTARES
  42. IceCube-201120A in the Cygnus region: No enhanced TeV gamma-ray flux detected by HAWC
  43. IceCube Alert 201124.34: Global MASTER-Net observations report
  44. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-201124A
  45. GRB 200826A: TNG and LBT constraints on a supernova bump
  46. GRB 201122A: Insight-HXMT/HE detection
  47. IceCube-201114A: DECam observations and candidate optical counterpart
  48. IceCube-201120A: Upper limits from a search for additional neutrino events in IceCube
  49. GRB 201015A L-band observations with e-MERLIN
  50. INTEGRAL Weak #8831 and #8832: AROMA-N Optical Observation
  51. Fermi-LAT Gamma-ray Observations of IceCube-201120A
  52. IceCube-201120A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  53. Fermi trigger No 627645769: Global MASTER-Net observations report
  54. IceCube-201120A: Swift-XRT non-detection of 4FGL J2028.6+4110e
  55. GRB 201015A radio afterglow with e-MERLIN
  56. Fermi GRB 201121A: Global MASTER-Net observations report
  57. GRB 201121B: Fermi GBM Final Real-time Localization
  58. GRB 201121A: BALROG localization (Fermi Trigger 627614994 / GRB 201121062)
  59. GRB 201121A: Fermi GBM Final Real-time Localization
  60. Fermi GRB 201120B: Global MASTER-Net observations report
  61. GRB 201120B: Fermi GBM Final Localization
  62. GRB 201120A: Fermi GBM Final Localization
  63. IceCube-201120A: Upper limits from Fermi-GBM Observations
  64. Fermi trigger No 627557935: Global MASTER-Net observations report
  65. Baksan Neutrino Observatory Alert 201120.43: Global MASTER-Net observations report
  66. IceCube Alert 201120.41: Global MASTER-Net observations report
  67. IceCube-201120A: IceCube observation of a high-energy neutrino candidate event
  68. ZTF20acozryr/AT2020yxz (GRB 201103B): SAO RAS optical observations
  69. ZTF20acozryr/AT2020yxz (GRB 201103B): correction to the GCN #28883 CrAO/ZTSh optical observations
  70. IceCube 201114A: Swift followup of Fermi J0703.5+0505
  71. GRB 201116A: CALET Gamma-Ray Burst Monitor detection
  72. INTEGRAL Weak#8825: AROMA-N Optical Observation
  73. Fermi trigger No 627438255: Global MASTER-Net observations report
  74. Konus-Wind detection of GRB 201116A
  75. Trigger 1007266: Swift detection of 1A 0535+262
  76. Fermi-LAT Gamma-ray Observations of IceCube-201114A
  77. GRB 201116A: NOT optical observations
  78. GRB 201116A: Swift-XRT afterglow detection
  79. GRB 201116A: OSN Afterglow Candidate
  80. Swift Trigger 1006917 is Be/X-ray binary pulsar 1A 0535+262
  81. IceCube Alert 201115.67: Global MASTER-Net observations report
  82. Fermi trigger No 627198169: Global MASTER-Net observations report
  83. IceCube-201115A: Upper limits from a search for additional neutrino events in IceCube
  84. IceCube-201114A: Upper limits from a search for additional neutrino events in IceCube
  85. IceCube-201115A: No significant detection in HAWC
  86. IceCube-201114A: No significant detection in HAWC
  87. GRB 201116A: Fermi-LAT detection
  88. GRB 201116A: Tiled Swift observations
  89. LAT GRB201116.03: Global MASTER-Net observations report
  90. IceCube-201115A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  91. IceCube-201114A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  92. INTEGRAL Weak#8811: AROMA-N Optical Observation
  93. IceCube-201115A: No neutrino counterpart candidates in ANTARES search
  94. IceCube Alert 201115.09: Global MASTER-Net observations report
  95. Fermi-LAT Gamma-ray Observations of IceCube-201115A
  96. GRB 201116A: BALROG localization (Fermi Trigger 627180592 / GRB 201116035)
  97. GRB 201116A: Fermi GBM Final Real-time Localization
  98. IceCube-201115A: not observable by Fermi-GBM
  99. Swift XRT observations of the Fermi-LAT source 4FGL J0658.6+0636, positionally consistent with the IceCube high-energy neutrino alert
  100. IceCube-201114A: Upper limits from Fermi GBM Observations

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