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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. VLASS identifies possible radio counterparts to IceCube-201115A, including a bright BL Lac candidate
  2. IceCube GCN alert 134701_49508272.amon retraction
  3. Swift-XRT observations of IceCube 201114A
  4. IceCube-201114A: No neutrino counterpart candidates in ANTARES search
  5. IceCube-201115A: IceCube observation of a high-energy neutrino candidate event
  6. IceCube Alert 201114.63: Global MASTER-Net observations report
  7. IceCube-201114A - IceCube observation of a high-energy neutrino candidate event
  8. ZTF20acozryr/AT2020yxz (GRB 201103B): CrAO/ZTSh optical observations
  9. GRB 201114A: AstroSat CZTI detection
  10. Fermi-LAT Gamma-ray Observations of NuEm-201107A
  11. ZTF20acozryr/AT2020yxz (GRB 201103B): Mondy continued optical observations
  12. Fermi GRB 201111A: Global MASTER-Net observations report
  13. Konus-Wind observation of GRB 201109A
  14. ZTF20acozryr/AT2020yxz (GRB 201103B): Flattening of the optical light curve
  15. Swift Trigger 1005428: Detection of SGR 1830-0645
  16. GRB 201111A: Fermi GBM Final Real-time Localization
  17. IPN triangulation of GRB 201109A (short)
  18. ZTF20acozryr (GRB 201103B): GROWTH-India Telescope optical observations
  19. ZTF20acozryr/AT2020yxz (GRB 201103B): Mondy, Kitab, TSHAO optical observations
  20. GRB 201109A: Fermi GBM detection
  21. GRB 201104A: AstroSat CZTI detection
  22. Konus-Wind observation of GRB 201103B
  23. GRB 201104B: continued TSHAO optical observation
  24. GRB 201104B: MITSuME Akeno optical observation
  25. Fermi GRB 201109A: Global MASTER-Net observations report
  26. GRB 201109A: Fermi GBM Final Real-time Localization
  27. Fermi GRB 201108A: Global MASTER-Net observations report
  28. GRB 201108A: Fermi GBM Final Real-time Localization
  29. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-201107A
  30. Konus-Wind detection of GRB 201105A
  31. GRB 201103B: GMG observation (2nd epoch)
  32. ZTF20acozryr/AT2020yxz (GRB 201103B): Assy optical observations
  33. GRB201103B: GMG observation
  34. GRB 201104B: 1.3m DFOT optical observations
  35. GRB 201104A: Swift-XRT observations
  36. Swift XRT and UVOT detection of ZTF20acozryr/AT2020yxz/GRB201103B
  37. GRB 201015A: Swift-XRT late time observations
  38. GRB 201104B: Kitab optical observations
  39. Correction to GCN 28843: GBM report of GRB 201105B should have been GRB 201105A
  40. GRB 201103B (ZTF20acozryr/AT2020yxz): Xinglong-2.16m optical observations
  41. Fermi trigger No 626247072: Global MASTER-Net observations report
  42. GRB 201104B: TSHAO optical observation
  43. GRB 201104B: Swift/UVOT Detection
  44. GRB 201104B: Swift-XRT refined Analysis
  45. Correcton to GCN 28848: Swift observes ZTF20acozryr
  46. GRB 201104C: Swift ToO observations
  47. GRB 201103B (ZTF20acozryr/AT2020yxz): VLT/X-shooter redshift
  48. GRB 201103B (ZTF20acozryr/AT2020yxz): Nanshan/NEXT-0.6m optical observations
  49. GRB 201105A: Swift detected burst and BAT refined analysis
  50. IPN triangulation of GRB 201103B (consistent with ZTF20acozryr/AT2020yxz)
  51. GRB 201105B: Fermi GBM observation
  52. GRB 201105A: BALROG localization (Fermi Trigger 626247072 / GRB 201105230)
  53. ZTF20acozryr/AT2020yxz: Zwicky Transient Facility discovery of a fast optical transient with no associated GRB
  54. GRB 201104B: VLT/X-shooter redshift
  55. GRB 201104B: Swift-BAT refined analysis
  56. Swift Trigger 1004219: Detection of SGR 1830-0645
  57. GRB 201104A: BALROG localization (Fermi Trigger 626140861 / GRB 201104001)
  58. GRB 201104C: Fermi GBM Final Real-time Localization
  59. GRB 201104A: Tiled Swift observations
  60. GRB 201103B: AGILE detection
  61. GRB 201104A: Fermi GBM observation
  62. GRB 201104A: AGILE/MCAL detection
  63. GRB 201104A: Fermi-LAT detection
  64. GRB 201104B: Swift/UVOT Detection
  65. GRB 201104B: MASTER optical observation
  66. GRB 201104B: Swift detection of a burst
  67. Fermi GRB 201104A: Global MASTER-Net observations report
  68. GRB 201104A: Fermi GBM Final Real-time Localization
  69. GRB 201015A: Late X-ray Detections with Chandra
  70. Fermi GRB 201103A: Global MASTER-Net observations report
  71. GRB 201103A: Fermi GBM Final Real-time Localization
  72. Swift GRB 201031A: Global MASTER-Net observations report
  73. Swift Trigger 1003313 (a.k.a. GRB 201031A) is not an astrophysical event
  74. Fermi GRB 201031B: Global MASTER-Net observations report
  75. GRB 201031B: BALROG localization (Fermi Trigger 625859489 / GRB 201031744)
  76. GRB 201031B: Fermi GBM Final Real-time Localization
  77. GRB 201031A: Swift detection of a burst
  78. GRB 201029A: Swift-BAT refined analysis
  79. IceCube 201021A: Swift follow-up of Fermi J1725.5+1312
  80. Swift GRB 201029A: Global MASTER-Net observations report
  81. GRB 201029A: Swift/UVOT Upper Limits
  82. GRB 201029A: Fermi GBM detection
  83. GRB 201029A: Swift-XRT refined Analysis
  84. GRB 201029A: BOOTES-1 optical upper limit
  85. GRB 201029A: Enhanced Swift-XRT position
  86. GRB 201029A: FRAM-ORM optical limit
  87. Fermi trigger No 625695596: Global MASTER-Net observations report
  88. GRB 201029A: Swift detection of a burst
  89. GRB 201027A: MITSuME Akeno optical upper limits
  90. GRB 201027A: Swift-BAT refined analysis
  91. GRB 201026A: Swift-BAT refined analysis
  92. GRB 201027A: Swift/UVOT Upper Limits
  93. GRB 201027A: Swift-XRT refined Analysis
  94. GRB 201026A: Fermi GBM detection
  95. GRB 201026A: Swift-XRT refined Analysis
  96. Baksan Neutrino Observatory Alert 201027.41: Global MASTER-Net observations report
  97. GRB 201027A: 1.5m OSN optical upper limit
  98. GRB 201026A: Swift/UVOT Upper Limits
  99. GRB 201027A: Enhanced Swift-XRT position
  100. GRB 201026A: Enhanced Swift-XRT position

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