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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-201114A
  2. GRB 201116A: NOT optical observations
  3. GRB 201116A: Swift-XRT afterglow detection
  4. GRB 201116A: OSN Afterglow Candidate
  5. Swift Trigger 1006917 is Be/X-ray binary pulsar 1A 0535+262
  6. IceCube Alert 201115.67: Global MASTER-Net observations report
  7. Fermi trigger No 627198169: Global MASTER-Net observations report
  8. IceCube-201115A: Upper limits from a search for additional neutrino events in IceCube
  9. IceCube-201114A: Upper limits from a search for additional neutrino events in IceCube
  10. IceCube-201115A: No significant detection in HAWC
  11. IceCube-201114A: No significant detection in HAWC
  12. GRB 201116A: Fermi-LAT detection
  13. GRB 201116A: Tiled Swift observations
  14. LAT GRB201116.03: Global MASTER-Net observations report
  15. IceCube-201115A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  16. IceCube-201114A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  17. INTEGRAL Weak#8811: AROMA-N Optical Observation
  18. IceCube-201115A: No neutrino counterpart candidates in ANTARES search
  19. IceCube Alert 201115.09: Global MASTER-Net observations report
  20. Fermi-LAT Gamma-ray Observations of IceCube-201115A
  21. GRB 201116A: BALROG localization (Fermi Trigger 627180592 / GRB 201116035)
  22. GRB 201116A: Fermi GBM Final Real-time Localization
  23. IceCube-201115A: not observable by Fermi-GBM
  24. Swift XRT observations of the Fermi-LAT source 4FGL J0658.6+0636, positionally consistent with the IceCube high-energy neutrino alert
  25. IceCube-201114A: Upper limits from Fermi GBM Observations
  26. VLASS identifies possible radio counterparts to IceCube-201115A, including a bright BL Lac candidate
  27. IceCube GCN alert 134701_49508272.amon retraction
  28. Swift-XRT observations of IceCube 201114A
  29. IceCube-201114A: No neutrino counterpart candidates in ANTARES search
  30. IceCube-201115A: IceCube observation of a high-energy neutrino candidate event
  31. IceCube Alert 201114.63: Global MASTER-Net observations report
  32. IceCube-201114A - IceCube observation of a high-energy neutrino candidate event
  33. ZTF20acozryr/AT2020yxz (GRB 201103B): CrAO/ZTSh optical observations
  34. GRB 201114A: AstroSat CZTI detection
  35. Fermi-LAT Gamma-ray Observations of NuEm-201107A
  36. ZTF20acozryr/AT2020yxz (GRB 201103B): Mondy continued optical observations
  37. Fermi GRB 201111A: Global MASTER-Net observations report
  38. Konus-Wind observation of GRB 201109A
  39. ZTF20acozryr/AT2020yxz (GRB 201103B): Flattening of the optical light curve
  40. Swift Trigger 1005428: Detection of SGR 1830-0645
  41. GRB 201111A: Fermi GBM Final Real-time Localization
  42. IPN triangulation of GRB 201109A (short)
  43. ZTF20acozryr (GRB 201103B): GROWTH-India Telescope optical observations
  44. ZTF20acozryr/AT2020yxz (GRB 201103B): Mondy, Kitab, TSHAO optical observations
  45. GRB 201109A: Fermi GBM detection
  46. GRB 201104A: AstroSat CZTI detection
  47. Konus-Wind observation of GRB 201103B
  48. GRB 201104B: continued TSHAO optical observation
  49. GRB 201104B: MITSuME Akeno optical observation
  50. Fermi GRB 201109A: Global MASTER-Net observations report
  51. GRB 201109A: Fermi GBM Final Real-time Localization
  52. Fermi GRB 201108A: Global MASTER-Net observations report
  53. GRB 201108A: Fermi GBM Final Real-time Localization
  54. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-201107A
  55. Konus-Wind detection of GRB 201105A
  56. GRB 201103B: GMG observation (2nd epoch)
  57. ZTF20acozryr/AT2020yxz (GRB 201103B): Assy optical observations
  58. GRB201103B: GMG observation
  59. GRB 201104B: 1.3m DFOT optical observations
  60. GRB 201104A: Swift-XRT observations
  61. Swift XRT and UVOT detection of ZTF20acozryr/AT2020yxz/GRB201103B
  62. GRB 201015A: Swift-XRT late time observations
  63. GRB 201104B: Kitab optical observations
  64. Correction to GCN 28843: GBM report of GRB 201105B should have been GRB 201105A
  65. GRB 201103B (ZTF20acozryr/AT2020yxz): Xinglong-2.16m optical observations
  66. Fermi trigger No 626247072: Global MASTER-Net observations report
  67. GRB 201104B: TSHAO optical observation
  68. GRB 201104B: Swift/UVOT Detection
  69. GRB 201104B: Swift-XRT refined Analysis
  70. Correcton to GCN 28848: Swift observes ZTF20acozryr
  71. GRB 201104C: Swift ToO observations
  72. GRB 201103B (ZTF20acozryr/AT2020yxz): VLT/X-shooter redshift
  73. GRB 201103B (ZTF20acozryr/AT2020yxz): Nanshan/NEXT-0.6m optical observations
  74. GRB 201105A: Swift detected burst and BAT refined analysis
  75. IPN triangulation of GRB 201103B (consistent with ZTF20acozryr/AT2020yxz)
  76. GRB 201105B: Fermi GBM observation
  77. GRB 201105A: BALROG localization (Fermi Trigger 626247072 / GRB 201105230)
  78. ZTF20acozryr/AT2020yxz: Zwicky Transient Facility discovery of a fast optical transient with no associated GRB
  79. GRB 201104B: VLT/X-shooter redshift
  80. GRB 201104B: Swift-BAT refined analysis
  81. Swift Trigger 1004219: Detection of SGR 1830-0645
  82. GRB 201104A: BALROG localization (Fermi Trigger 626140861 / GRB 201104001)
  83. GRB 201104C: Fermi GBM Final Real-time Localization
  84. GRB 201104A: Tiled Swift observations
  85. GRB 201103B: AGILE detection
  86. GRB 201104A: Fermi GBM observation
  87. GRB 201104A: AGILE/MCAL detection
  88. GRB 201104A: Fermi-LAT detection
  89. GRB 201104B: Swift/UVOT Detection
  90. GRB 201104B: MASTER optical observation
  91. GRB 201104B: Swift detection of a burst
  92. Fermi GRB 201104A: Global MASTER-Net observations report
  93. GRB 201104A: Fermi GBM Final Real-time Localization
  94. GRB 201015A: Late X-ray Detections with Chandra
  95. Fermi GRB 201103A: Global MASTER-Net observations report
  96. GRB 201103A: Fermi GBM Final Real-time Localization
  97. Swift GRB 201031A: Global MASTER-Net observations report
  98. Swift Trigger 1003313 (a.k.a. GRB 201031A) is not an astrophysical event
  99. Fermi GRB 201031B: Global MASTER-Net observations report
  100. GRB 201031B: BALROG localization (Fermi Trigger 625859489 / GRB 201031744)

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