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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. IceCube-201115A: No neutrino counterpart candidates in ANTARES search
  2. IceCube Alert 201115.09: Global MASTER-Net observations report
  3. Fermi-LAT Gamma-ray Observations of IceCube-201115A
  4. GRB 201116A: BALROG localization (Fermi Trigger 627180592 / GRB 201116035)
  5. GRB 201116A: Fermi GBM Final Real-time Localization
  6. IceCube-201115A: not observable by Fermi-GBM
  7. Swift XRT observations of the Fermi-LAT source 4FGL J0658.6+0636, positionally consistent with the IceCube high-energy neutrino alert
  8. IceCube-201114A: Upper limits from Fermi GBM Observations
  9. VLASS identifies possible radio counterparts to IceCube-201115A, including a bright BL Lac candidate
  10. IceCube GCN alert 134701_49508272.amon retraction
  11. Swift-XRT observations of IceCube 201114A
  12. IceCube-201114A: No neutrino counterpart candidates in ANTARES search
  13. IceCube-201115A: IceCube observation of a high-energy neutrino candidate event
  14. IceCube Alert 201114.63: Global MASTER-Net observations report
  15. IceCube-201114A - IceCube observation of a high-energy neutrino candidate event
  16. ZTF20acozryr/AT2020yxz (GRB 201103B): CrAO/ZTSh optical observations
  17. GRB 201114A: AstroSat CZTI detection
  18. Fermi-LAT Gamma-ray Observations of NuEm-201107A
  19. ZTF20acozryr/AT2020yxz (GRB 201103B): Mondy continued optical observations
  20. Fermi GRB 201111A: Global MASTER-Net observations report
  21. Konus-Wind observation of GRB 201109A
  22. ZTF20acozryr/AT2020yxz (GRB 201103B): Flattening of the optical light curve
  23. Swift Trigger 1005428: Detection of SGR 1830-0645
  24. GRB 201111A: Fermi GBM Final Real-time Localization
  25. IPN triangulation of GRB 201109A (short)
  26. ZTF20acozryr (GRB 201103B): GROWTH-India Telescope optical observations
  27. ZTF20acozryr/AT2020yxz (GRB 201103B): Mondy, Kitab, TSHAO optical observations
  28. GRB 201109A: Fermi GBM detection
  29. GRB 201104A: AstroSat CZTI detection
  30. Konus-Wind observation of GRB 201103B
  31. GRB 201104B: continued TSHAO optical observation
  32. GRB 201104B: MITSuME Akeno optical observation
  33. Fermi GRB 201109A: Global MASTER-Net observations report
  34. GRB 201109A: Fermi GBM Final Real-time Localization
  35. Fermi GRB 201108A: Global MASTER-Net observations report
  36. GRB 201108A: Fermi GBM Final Real-time Localization
  37. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-201107A
  38. Konus-Wind detection of GRB 201105A
  39. GRB 201103B: GMG observation (2nd epoch)
  40. ZTF20acozryr/AT2020yxz (GRB 201103B): Assy optical observations
  41. GRB201103B: GMG observation
  42. GRB 201104B: 1.3m DFOT optical observations
  43. GRB 201104A: Swift-XRT observations
  44. Swift XRT and UVOT detection of ZTF20acozryr/AT2020yxz/GRB201103B
  45. GRB 201015A: Swift-XRT late time observations
  46. GRB 201104B: Kitab optical observations
  47. Correction to GCN 28843: GBM report of GRB 201105B should have been GRB 201105A
  48. GRB 201103B (ZTF20acozryr/AT2020yxz): Xinglong-2.16m optical observations
  49. Fermi trigger No 626247072: Global MASTER-Net observations report
  50. GRB 201104B: TSHAO optical observation
  51. GRB 201104B: Swift/UVOT Detection
  52. GRB 201104B: Swift-XRT refined Analysis
  53. Correcton to GCN 28848: Swift observes ZTF20acozryr
  54. GRB 201104C: Swift ToO observations
  55. GRB 201103B (ZTF20acozryr/AT2020yxz): VLT/X-shooter redshift
  56. GRB 201103B (ZTF20acozryr/AT2020yxz): Nanshan/NEXT-0.6m optical observations
  57. GRB 201105A: Swift detected burst and BAT refined analysis
  58. IPN triangulation of GRB 201103B (consistent with ZTF20acozryr/AT2020yxz)
  59. GRB 201105B: Fermi GBM observation
  60. GRB 201105A: BALROG localization (Fermi Trigger 626247072 / GRB 201105230)
  61. ZTF20acozryr/AT2020yxz: Zwicky Transient Facility discovery of a fast optical transient with no associated GRB
  62. GRB 201104B: VLT/X-shooter redshift
  63. GRB 201104B: Swift-BAT refined analysis
  64. Swift Trigger 1004219: Detection of SGR 1830-0645
  65. GRB 201104A: BALROG localization (Fermi Trigger 626140861 / GRB 201104001)
  66. GRB 201104C: Fermi GBM Final Real-time Localization
  67. GRB 201104A: Tiled Swift observations
  68. GRB 201103B: AGILE detection
  69. GRB 201104A: Fermi GBM observation
  70. GRB 201104A: AGILE/MCAL detection
  71. GRB 201104A: Fermi-LAT detection
  72. GRB 201104B: Swift/UVOT Detection
  73. GRB 201104B: MASTER optical observation
  74. GRB 201104B: Swift detection of a burst
  75. Fermi GRB 201104A: Global MASTER-Net observations report
  76. GRB 201104A: Fermi GBM Final Real-time Localization
  77. GRB 201015A: Late X-ray Detections with Chandra
  78. Fermi GRB 201103A: Global MASTER-Net observations report
  79. GRB 201103A: Fermi GBM Final Real-time Localization
  80. Swift GRB 201031A: Global MASTER-Net observations report
  81. Swift Trigger 1003313 (a.k.a. GRB 201031A) is not an astrophysical event
  82. Fermi GRB 201031B: Global MASTER-Net observations report
  83. GRB 201031B: BALROG localization (Fermi Trigger 625859489 / GRB 201031744)
  84. GRB 201031B: Fermi GBM Final Real-time Localization
  85. GRB 201031A: Swift detection of a burst
  86. GRB 201029A: Swift-BAT refined analysis
  87. IceCube 201021A: Swift follow-up of Fermi J1725.5+1312
  88. Swift GRB 201029A: Global MASTER-Net observations report
  89. GRB 201029A: Swift/UVOT Upper Limits
  90. GRB 201029A: Fermi GBM detection
  91. GRB 201029A: Swift-XRT refined Analysis
  92. GRB 201029A: BOOTES-1 optical upper limit
  93. GRB 201029A: Enhanced Swift-XRT position
  94. GRB 201029A: FRAM-ORM optical limit
  95. Fermi trigger No 625695596: Global MASTER-Net observations report
  96. GRB 201029A: Swift detection of a burst
  97. GRB 201027A: MITSuME Akeno optical upper limits
  98. GRB 201027A: Swift-BAT refined analysis
  99. GRB 201026A: Swift-BAT refined analysis
  100. GRB 201027A: Swift/UVOT Upper Limits

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