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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 GRB 230207A: Global MASTER-Net observations report
  2. GRB 230207A: Fermi GBM Final Real-time Localization
  3. GRB 230204B: LCOGT Optical Upper Limits
  4. GRB 230204B: Swift/UVOT Upper Limits
  5. Fermi trigger No 697403223: Global MASTER-Net observations report
  6. Fermi trigger No 697396830: Global MASTER-Net observations report
  7. GRB 230205A: Swift/UVOT Upper Limits
  8. GRB 230204B: Fermi GBM detection
  9. Fermi Gamma-ray Burst Monitor triggers due to recent activity of RX J0440.9+4431 (LS V +44 17)
  10. GRB 230205A: LCOGT Optical Upper Limits
  11. GRB 230204B: Swift-XRT afterglow detection
  12. GRB 230204B: 3.6m DOT optical observation
  13. GRB 230205A: SVOM/C-GFT optical upper limit
  14. GRB 230205A: OHP/T193 optical observations
  15. GRB 230204B: VLT/X-shooter redshift
  16. GRB 230205A: Swift-BAT refined analysis (T90 = 2.3 s)
  17. GRB 230204A: Swift-BAT refined analysis
  18. GRB 230204B: ATLAS detection of the optical afterglow and a projected location in a nearby galaxy group
  19. GRB 230205A: Swift-XRT refined Analysis
  20. GRB 230204B: Swift ToO observations
  21. GRB 230205A: Enhanced Swift-XRT position
  22. GRB 230205A: BOOTES-5/JGT early optical upper limit
  23. GRB 230204B: Detection by GRBAlpha
  24. GRB 230204B: AGILE detection
  25. GRB 230205A: Swift detection of a burst
  26. IceCube-230201A: BOOTES-4/MET Optical Upper Limits
  27. GRB 230204B: GIT discovery of the likely optical afterglow
  28. GRB 230204B: AstroSat CZTI detection
  29. GRB 230204B: Swift/BAT-GUANO detection outside the coded FOV
  30. GRB 230204A: Swift/UVOT Upper Limits
  31. GRB 230204B: MAXI/GSC detection
  32. GRB 230204A: Swift-XRT refined Analysis
  33. GRB 230204A/Swift J1552.8-5055: LCOGT Optical Counterpart Candidate
  34. Fermi trigger No 697208885: Global MASTER-Net observations report
  35. GRB 230204A: Enhanced Swift-XRT position
  36. GRB 230204A: Swift detection of a possible burst (or possible transient Swift J1552.8-5055)
  37. GRB 230201B: TURBO Optical Upper Limits
  38. Fermi Gamma-ray Burst Monitor trigger 230203275 / 697098930 is not a GRB
  39. Fermi trigger No 697098930: Global MASTER-Net observations report
  40. IceCube-230201A: Upper limits from a search for additional neutrino events in IceCube
  41. ZTF23aabmzlp/AT2023azs: Lulin 1m LOT optical observations
  42. GRB 221216A: Swift-BAT refined analysis
  43. ZTF23aabmzlp/AT2023azs: VLA radio detection
  44. ZTF23aaarlti/AT2023avj: AMI-LA radio detection
  45. ZTF23aabmzlp/AT2023azs: AMI-LA radio upper limit
  46. IceCube Alert 230201.26: Global MASTER-Net observations report
  47. Fermi GRB 230201B: Global MASTER-Net observations report
  48. Fermi-LAT gamma-ray observations of IceCube-230201A
  49. GRB 230201B: Fermi GBM Final Real-time Localization
  50. GRB 230126A: Detection by VZLUSAT-2
  51. Fermi GRB 230201A: Global MASTER-Net observations report
  52. IceCube-230201A - IceCube observation of a high-energy neutrino candidate track-like event
  53. GRB 221009A: radio afterglow detection with the EVN
  54. GRB 230201A: Fermi GBM Final Real-time Localization
  55. ZTF23aabmzlp/AT2023azs: LCOGT Optical Detection
  56. ZTF23aaarlti/AT2023avj: Assy continued optical observations
  57. ZTF23aabmzlp/AT2023azs: Mondy and AbAO optical observations
  58. AT2023avj: X-ray Detection with Swift/XRT
  59. ZTF23aabmzlp/AT2023azs: 1.3m DFOT optical observations
  60. GRB 230129A: AstroSat CZTI detection
  61. GRB 230128A: AstroSat CZTI detection
  62. GRB 230130A: Fermi GBM Final Real-time Localization
  63. ZTF23aaarlti/AT2023avj: VLA radio detection
  64. GRB 230129A: Fermi GBM Final Real-time Localization
  65. GRB 230128A: Fermi GBM Final Real-time Localization
  66. ZTF23aabmzlp/AT2023azs: GIT confirmation of the likely afterglow
  67. ZTF23aabmzlp/AT2023azs: Zwicky Transient Facility discovery of a fast optical transient
  68. IceCube-230122A: BOOTES-2/TELMA Optical Upper Limit
  69. AT2023avj ZTF Candidate: Assy optical observations
  70. ZTF and LT Observations of AT2023avj, a Candidate Optical Afterglow
  71. GRB 230126A: Fermi GBM Final Real-time Localization
  72. Swift-XRT observations of NuEm-230125A
  73. Trigger 1150965: Swift detection of LS V +44 17
  74. GRB 230124A: Fermi GBM Observation
  75. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230125A
  76. GRB 230124A: Swift/BAT-GUANO detection outside the coded FOV
  77. IceCube-230122A: Upper limits from a search for additional neutrino events in IceCube
  78. GRB 230114B: Detection by VZLUSAT-2
  79. GRB 230123A: LCOGT Optical Upper Limits
  80. Fermi GRB 230124A: Global MASTER-Net observations report
  81. GRB 230124A: Fermi GBM Final Real-time Localization
  82. GRB 230123A: Swift-BAT refined analysis
  83. GRB 230122A: Swift/BAT-GUANO detection
  84. Fermi-LAT gamma-ray observations of IceCube-230122A
  85. GRB 230123A: Swift/UVOT Upper Limits
  86. GRB 230123A: Swift-XRT refined Analysis
  87. GRB 230123A: Enhanced Swift-XRT position
  88. GRB 230123A: Zadko observatory - Gingin optical observations
  89. GRB 230116C: Swift-XRT observations
  90. GRB 230123A: Swift detection of a burst
  91. IceCube Alert 230122.16: Global MASTER-Net observations report
  92. IceCube-230122A - IceCube observation of a high-energy neutrino candidate track-like event
  93. GRB 230116B: Fermi GBM observation
  94. Trigger 1150107: Swift detection of LS V +44 17
  95. GRB 230120A: AstroSat CZTI detection
  96. IPN triangulation of GRB 230116B (short)
  97. GRB 230119A: CALET Gamma-Ray Burst Monitor detection
  98. GRB 230116D: 3.6m DOT optical upper limit
  99. GRB 230119A: Fermi GBM Final Real-time Localization
  100. Fermi GRB 230118A: Global MASTER-Net observations report

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