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

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