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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 201031A: Swift detection of a burst
  2. GRB 201029A: Swift-BAT refined analysis
  3. IceCube 201021A: Swift follow-up of Fermi J1725.5+1312
  4. Swift GRB 201029A: Global MASTER-Net observations report
  5. GRB 201029A: Swift/UVOT Upper Limits
  6. GRB 201029A: Fermi GBM detection
  7. GRB 201029A: Swift-XRT refined Analysis
  8. GRB 201029A: BOOTES-1 optical upper limit
  9. GRB 201029A: Enhanced Swift-XRT position
  10. GRB 201029A: FRAM-ORM optical limit
  11. Fermi trigger No 625695596: Global MASTER-Net observations report
  12. GRB 201029A: Swift detection of a burst
  13. GRB 201027A: MITSuME Akeno optical upper limits
  14. GRB 201027A: Swift-BAT refined analysis
  15. GRB 201026A: Swift-BAT refined analysis
  16. GRB 201027A: Swift/UVOT Upper Limits
  17. GRB 201027A: Swift-XRT refined Analysis
  18. GRB 201026A: Fermi GBM detection
  19. GRB 201026A: Swift-XRT refined Analysis
  20. Baksan Neutrino Observatory Alert 201027.41: Global MASTER-Net observations report
  21. GRB 201027A: 1.5m OSN optical upper limit
  22. GRB 201026A: Swift/UVOT Upper Limits
  23. GRB 201027A: Enhanced Swift-XRT position
  24. GRB 201026A: Enhanced Swift-XRT position
  25. GRB 201026A: FRAM-ORM optical detection limit
  26. GRB 201020A: 1.3m DFOT, optical upper limits
  27. GRB 201027A: Swift detection of a burst
  28. Swift GRB201027.05: Global MASTER-Net observations report
  29. GRB 201026A: NanShan/NEXT-0.6m optical upper limit
  30. GRB 201026A: NOT optical upper limits
  31. GRB 201026A: Swift detection of a burst
  32. Swift GRB201026.94: Global MASTER-Net observations report
  33. GRB 201024A: 1.3m DFOT optical observations
  34. GRB 201020B: 1.3m DFOT continued optical follow-up observations
  35. GRB201024A: correction to GCN28777 - there was no rebrightening
  36. GRB 201024A: MITSuME Akeno optical upper limits
  37. GRB 201024A: Swift-BAT refined analysis
  38. GRB201024A: rebrightening after initial steep decline
  39. GRB 201020B: HCT and GIT continued optical follow-up observations
  40. GRB 201024A: Swift-XRT refined Analysis
  41. GRB 201024A: Swift/UVOT Detection
  42. GRB 201020B: follow-up observations with Savelli Telescope
  43. GRB 201020B: 1.3m DFOT optical observations
  44. GRB 201024A: VIRT optical observations
  45. GRB 201024A: Enhanced Swift-XRT position
  46. GRB 201020B: follow-up observations at Konkoly
  47. GRB 201020B: continued Mondy optical observations
  48. GRB 200901A: FRAM-Auger optical limit
  49. GRB 201024A: FRAM-ORM afterglow detection
  50. GRB 201020B: Redshift from GTC/OSIRIS
  51. GRB 201024A: Redshift from GTC/OSIRIS
  52. GRB 201024A: BOOTES-2/TELMA early optical observation and 1.5m OSN follow-up
  53. GRB 201024A: MASTER correction to GCN 28760
  54. GRB 201024A: Swift detection of a burst with an optical afterglow
  55. Swift GRB201024A: Global MASTER-Net OT detection
  56. Swift GRB201024.12: Global MASTER-Net observations report
  57. IceCube-201021A: No significant detection in HAWC
  58. IceCube-201021A: One candidate counterpart from the Zwicky Transient Facility
  59. IceCube-201021A: Optical counterpart of WISEA J172314.13+142101.5
  60. GRB 201021C: Swift-BAT refined analysis
  61. GRB 201021C: Swift-XRT refined Analysis
  62. GRB 201020B: GROWTH-India Telescope optical observations
  63. Baksan Neutrino Observatory Alert 201022.66: Global MASTER-Net observations report
  64. Fermi-LAT Gamma-ray Observations of IceCube-201021A and detection of a new gamma-ray source, Fermi J1725.5+1312
  65. GRB 201020B: Konkoly Obs. optical detection
  66. Swift-XRT observations of IceCube 201021A (2)
  67. GRB 201021C: Fermi GBM detection
  68. GRB 201020A: GROWTH-India Telescope late-time optical upper limit
  69. IceCube-201021A: Upper limits from a search for additional neutrino events in IceCube
  70. GRB 201021C: Swift/UVOT Detection
  71. Konus-Wind detection of GRB 201020A
  72. GRB 201020B: Swift/UVOT Detection
  73. GRB 201020A: Swift/UVOT Observations
  74. GRB 201014A: 2.0m HCT upper limit
  75. GRB 201020B: Swift-XRT afterglow detection
  76. GRB 201021C: VLT/X-shooter redshift
  77. IceCube-201021A: No neutrino counterpart candidates in ANTARES search
  78. GRB 201020A: VIRT optical observations
  79. GRB 201021C: Enhanced Swift-XRT position
  80. IceCube-201021A: Upper limits from Fermi-GBM Observations
  81. HAWC-201019A: not observable by Fermi-GBM
  82. GRB 201021C: MASTER optical synchronously observation
  83. IceCube-201021A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  84. Swift GRB201021.85: Global MASTER-Net observations report
  85. GRB 201021C: Swift detection of a burst with an optical counterpart
  86. HAWC-201019A: No Neutrino Counterpart detected with ANTARES
  87. MAXI GRB201021.68: Global MASTER-Net observations report
  88. GRB200826A: GMOS-N detection of a supernova bump
  89. GRB 201021B MAXI/GSC detection
  90. GRB 201020B: Mondy optical observations
  91. Swift-XRT observations of IceCube 201021A
  92. Konus-Wind detection of GRB 201020B
  93. IceCube Alert 201021.28: Global MASTER-Net observations report
  94. GRB 201015A: SAO RAS optical observations
  95. GRB 201020B: Swift ToO observations
  96. GRB 201020B: Nanshan/NEXT optical afterglow confirmation
  97. GRB 201020B: MASTER bright optical afterglow detection
  98. GRB 201020A: Redshift from GTC/OSIRIS
  99. GRB 201020B: Fermi-LAT detection
  100. IceCube-201021A: IceCube observation of a high-energy neutrino candidate event

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