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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').
  1. GRB 230205A: Swift-XRT refined Analysis
  2. GRB 230204B: Swift ToO observations
  3. GRB 230205A: Enhanced Swift-XRT position
  4. GRB 230205A: BOOTES-5/JGT early optical upper limit
  5. GRB 230204B: Detection by GRBAlpha
  6. GRB 230204B: AGILE detection
  7. GRB 230205A: Swift detection of a burst
  8. IceCube-230201A: BOOTES-4/MET Optical Upper Limits
  9. GRB 230204B: GIT discovery of the likely optical afterglow
  10. GRB 230204B: AstroSat CZTI detection
  11. GRB 230204B: Swift/BAT-GUANO detection outside the coded FOV
  12. GRB 230204A: Swift/UVOT Upper Limits
  13. GRB 230204B: MAXI/GSC detection
  14. GRB 230204A: Swift-XRT refined Analysis
  15. GRB 230204A/Swift J1552.8-5055: LCOGT Optical Counterpart Candidate
  16. Fermi trigger No 697208885: Global MASTER-Net observations report
  17. GRB 230204A: Enhanced Swift-XRT position
  18. GRB 230204A: Swift detection of a possible burst (or possible transient Swift J1552.8-5055)
  19. GRB 230201B: TURBO Optical Upper Limits
  20. Fermi Gamma-ray Burst Monitor trigger 230203275 / 697098930 is not a GRB
  21. Fermi trigger No 697098930: Global MASTER-Net observations report
  22. IceCube-230201A: Upper limits from a search for additional neutrino events in IceCube
  23. ZTF23aabmzlp/AT2023azs: Lulin 1m LOT optical observations
  24. GRB 221216A: Swift-BAT refined analysis
  25. ZTF23aabmzlp/AT2023azs: VLA radio detection
  26. ZTF23aaarlti/AT2023avj: AMI-LA radio detection
  27. ZTF23aabmzlp/AT2023azs: AMI-LA radio upper limit
  28. IceCube Alert 230201.26: Global MASTER-Net observations report
  29. Fermi GRB 230201B: Global MASTER-Net observations report
  30. Fermi-LAT gamma-ray observations of IceCube-230201A
  31. GRB 230201B: Fermi GBM Final Real-time Localization
  32. GRB 230126A: Detection by VZLUSAT-2
  33. Fermi GRB 230201A: Global MASTER-Net observations report
  34. IceCube-230201A - IceCube observation of a high-energy neutrino candidate track-like event
  35. GRB 221009A: radio afterglow detection with the EVN
  36. GRB 230201A: Fermi GBM Final Real-time Localization
  37. ZTF23aabmzlp/AT2023azs: LCOGT Optical Detection
  38. ZTF23aaarlti/AT2023avj: Assy continued optical observations
  39. ZTF23aabmzlp/AT2023azs: Mondy and AbAO optical observations
  40. AT2023avj: X-ray Detection with Swift/XRT
  41. ZTF23aabmzlp/AT2023azs: 1.3m DFOT optical observations
  42. GRB 230129A: AstroSat CZTI detection
  43. GRB 230128A: AstroSat CZTI detection
  44. GRB 230130A: Fermi GBM Final Real-time Localization
  45. ZTF23aaarlti/AT2023avj: VLA radio detection
  46. GRB 230129A: Fermi GBM Final Real-time Localization
  47. GRB 230128A: Fermi GBM Final Real-time Localization
  48. ZTF23aabmzlp/AT2023azs: GIT confirmation of the likely afterglow
  49. ZTF23aabmzlp/AT2023azs: Zwicky Transient Facility discovery of a fast optical transient
  50. IceCube-230122A: BOOTES-2/TELMA Optical Upper Limit
  51. AT2023avj ZTF Candidate: Assy optical observations
  52. ZTF and LT Observations of AT2023avj, a Candidate Optical Afterglow
  53. GRB 230126A: Fermi GBM Final Real-time Localization
  54. Swift-XRT observations of NuEm-230125A
  55. Trigger 1150965: Swift detection of LS V +44 17
  56. GRB 230124A: Fermi GBM Observation
  57. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230125A
  58. GRB 230124A: Swift/BAT-GUANO detection outside the coded FOV
  59. IceCube-230122A: Upper limits from a search for additional neutrino events in IceCube
  60. GRB 230114B: Detection by VZLUSAT-2
  61. GRB 230123A: LCOGT Optical Upper Limits
  62. Fermi GRB 230124A: Global MASTER-Net observations report
  63. GRB 230124A: Fermi GBM Final Real-time Localization
  64. GRB 230123A: Swift-BAT refined analysis
  65. GRB 230122A: Swift/BAT-GUANO detection
  66. Fermi-LAT gamma-ray observations of IceCube-230122A
  67. GRB 230123A: Swift/UVOT Upper Limits
  68. GRB 230123A: Swift-XRT refined Analysis
  69. GRB 230123A: Enhanced Swift-XRT position
  70. GRB 230123A: Zadko observatory - Gingin optical observations
  71. GRB 230116C: Swift-XRT observations
  72. GRB 230123A: Swift detection of a burst
  73. IceCube Alert 230122.16: Global MASTER-Net observations report
  74. IceCube-230122A - IceCube observation of a high-energy neutrino candidate track-like event
  75. GRB 230116B: Fermi GBM observation
  76. Trigger 1150107: Swift detection of LS V +44 17
  77. GRB 230120A: AstroSat CZTI detection
  78. IPN triangulation of GRB 230116B (short)
  79. GRB 230119A: CALET Gamma-Ray Burst Monitor detection
  80. GRB 230116D: 3.6m DOT optical upper limit
  81. GRB 230119A: Fermi GBM Final Real-time Localization
  82. Fermi GRB 230118A: Global MASTER-Net observations report
  83. GRB 230118A: Fermi GBM Final Real-time Localization
  84. GRB 230116D: Swift-BAT refined analysis
  85. GRB 230116C: Swift-BAT refined analysis
  86. GRB 230116D: SAO RAS further observations
  87. GRB 230116D: SAO RAS photometry
  88. GRB 230116D: KGO RC-25 optical observations
  89. GRB 230116D: Sintez-Newton/CrAO optical observations
  90. GRB 230116D: LCOGT Optical Upper Limit
  91. GRB 230116D: SAO RAS redshift
  92. Fermi trigger No 695569700: Global MASTER-Net observations report
  93. GRB 230116D: Swift-XRT refined Analysis
  94. Fermi GRB 230117A: Global MASTER-Net observations report
  95. GRB 230117A: Fermi GBM Final Real-time Localization
  96. GRB 230116D: GIT optical follow-up
  97. GRB 230116D: GIT optical follow-up
  98. GRB 230116D: Enhanced Swift-XRT position
  99. GRB 230116D: SAO RAS observations of OT brightening
  100. GRB 230116D: Sintez-Newton/CrAO optical afterglow detection

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