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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-LAT Gamma-ray Observations of IceCube-201130A
  2. IceCube-201130A: Not observable by Fermi-GBM
  3. GRB 201201A: DDOTI Observations
  4. Fermi GRB 201201A: Global MASTER-Net observations report
  5. GRB 201128B: Swift ToO observations
  6. Swift-XRT observations of IceCube 201130A
  7. GRB 201201A: Fermi GBM Final Real-time Localization
  8. GRB 201128B: Swift/BAT-GUANO detection and arcminute localization
  9. GRB 201128A: Swift/UVOT Upper Limits
  10. IceCube-201130A: IceCube observation of a high-energy neutrino candidate event
  11. IceCube Alert 201130.85: Global MASTER-Net observations report
  12. GRB 201130A: DDOTI Observations
  13. Fermi GRB 201130A: Global MASTER-Net observations report
  14. GRB 201130A: Fermi GBM Final Real-time Localization
  15. Baksan Neutrino Observatory Alert 201128.90: Global MASTER-Net observations report
  16. GRB 201128A: Swift-BAT refined analysis
  17. GRB 201128A: Swift-XRT refined Analysis
  18. Fermi trigger No 628278856: Global MASTER-Net observations report
  19. GRB 201128A: Enhanced Swift-XRT position
  20. GRB 201128A: DDOTI Observations
  21. GRB 201128A: Swift detection of a burst
  22. Fermi trigger No 628140709: DDOTI/OAN optical observations report
  23. Fermi trigger No 628140709: Global MASTER-Net observations report
  24. IceCube-201114A: Updated photometry for three DECam candidate optical counterparts
  25. GRB 201121A: Insight-HXMT/HE detection
  26. AMON IC_HAWC NuEm-201124A: No Neutrino Counterpart detected with ANTARES
  27. IceCube-201120A in the Cygnus region: No enhanced TeV gamma-ray flux detected by HAWC
  28. IceCube Alert 201124.34: Global MASTER-Net observations report
  29. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-201124A
  30. GRB 200826A: TNG and LBT constraints on a supernova bump
  31. GRB 201122A: Insight-HXMT/HE detection
  32. IceCube-201114A: DECam observations and candidate optical counterpart
  33. IceCube-201120A: Upper limits from a search for additional neutrino events in IceCube
  34. GRB 201015A L-band observations with e-MERLIN
  35. INTEGRAL Weak #8831 and #8832: AROMA-N Optical Observation
  36. Fermi-LAT Gamma-ray Observations of IceCube-201120A
  37. IceCube-201120A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  38. Fermi trigger No 627645769: Global MASTER-Net observations report
  39. IceCube-201120A: Swift-XRT non-detection of 4FGL J2028.6+4110e
  40. GRB 201015A radio afterglow with e-MERLIN
  41. Fermi GRB 201121A: Global MASTER-Net observations report
  42. GRB 201121B: Fermi GBM Final Real-time Localization
  43. GRB 201121A: BALROG localization (Fermi Trigger 627614994 / GRB 201121062)
  44. GRB 201121A: Fermi GBM Final Real-time Localization
  45. Fermi GRB 201120B: Global MASTER-Net observations report
  46. GRB 201120B: Fermi GBM Final Localization
  47. GRB 201120A: Fermi GBM Final Localization
  48. IceCube-201120A: Upper limits from Fermi-GBM Observations
  49. Fermi trigger No 627557935: Global MASTER-Net observations report
  50. Baksan Neutrino Observatory Alert 201120.43: Global MASTER-Net observations report
  51. IceCube Alert 201120.41: Global MASTER-Net observations report
  52. IceCube-201120A: IceCube observation of a high-energy neutrino candidate event
  53. ZTF20acozryr/AT2020yxz (GRB 201103B): SAO RAS optical observations
  54. ZTF20acozryr/AT2020yxz (GRB 201103B): correction to the GCN #28883 CrAO/ZTSh optical observations
  55. IceCube 201114A: Swift followup of Fermi J0703.5+0505
  56. GRB 201116A: CALET Gamma-Ray Burst Monitor detection
  57. INTEGRAL Weak#8825: AROMA-N Optical Observation
  58. Fermi trigger No 627438255: Global MASTER-Net observations report
  59. Konus-Wind detection of GRB 201116A
  60. Trigger 1007266: Swift detection of 1A 0535+262
  61. Fermi-LAT Gamma-ray Observations of IceCube-201114A
  62. GRB 201116A: NOT optical observations
  63. GRB 201116A: Swift-XRT afterglow detection
  64. GRB 201116A: OSN Afterglow Candidate
  65. Swift Trigger 1006917 is Be/X-ray binary pulsar 1A 0535+262
  66. IceCube Alert 201115.67: Global MASTER-Net observations report
  67. Fermi trigger No 627198169: Global MASTER-Net observations report
  68. IceCube-201115A: Upper limits from a search for additional neutrino events in IceCube
  69. IceCube-201114A: Upper limits from a search for additional neutrino events in IceCube
  70. IceCube-201115A: No significant detection in HAWC
  71. IceCube-201114A: No significant detection in HAWC
  72. GRB 201116A: Fermi-LAT detection
  73. GRB 201116A: Tiled Swift observations
  74. LAT GRB201116.03: Global MASTER-Net observations report
  75. IceCube-201115A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  76. IceCube-201114A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  77. INTEGRAL Weak#8811: AROMA-N Optical Observation
  78. IceCube-201115A: No neutrino counterpart candidates in ANTARES search
  79. IceCube Alert 201115.09: Global MASTER-Net observations report
  80. Fermi-LAT Gamma-ray Observations of IceCube-201115A
  81. GRB 201116A: BALROG localization (Fermi Trigger 627180592 / GRB 201116035)
  82. GRB 201116A: Fermi GBM Final Real-time Localization
  83. IceCube-201115A: not observable by Fermi-GBM
  84. Swift XRT observations of the Fermi-LAT source 4FGL J0658.6+0636, positionally consistent with the IceCube high-energy neutrino alert
  85. IceCube-201114A: Upper limits from Fermi GBM Observations
  86. VLASS identifies possible radio counterparts to IceCube-201115A, including a bright BL Lac candidate
  87. IceCube GCN alert 134701_49508272.amon retraction
  88. Swift-XRT observations of IceCube 201114A
  89. IceCube-201114A: No neutrino counterpart candidates in ANTARES search
  90. IceCube-201115A: IceCube observation of a high-energy neutrino candidate event
  91. IceCube Alert 201114.63: Global MASTER-Net observations report
  92. IceCube-201114A - IceCube observation of a high-energy neutrino candidate event
  93. ZTF20acozryr/AT2020yxz (GRB 201103B): CrAO/ZTSh optical observations
  94. GRB 201114A: AstroSat CZTI detection
  95. Fermi-LAT Gamma-ray Observations of NuEm-201107A
  96. ZTF20acozryr/AT2020yxz (GRB 201103B): Mondy continued optical observations
  97. Fermi GRB 201111A: Global MASTER-Net observations report
  98. Konus-Wind observation of GRB 201109A
  99. ZTF20acozryr/AT2020yxz (GRB 201103B): Flattening of the optical light curve
  100. Swift Trigger 1005428: Detection of SGR 1830-0645

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