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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. GRB 230216A: Enhanced Swift-XRT position
  2. GRB 230216A: AKO Upper Limit
  3. GRB 230216A: Zadko observatory - Gingin optical observations
  4. GRB 230216A: Swift detection of a burst
  5. Fermi GRB 230215A: Global MASTER-Net observations report
  6. GRB 230215A: Fermi GBM Final Real-time Localization
  7. GRB 230209B: AGILE detection
  8. GRB 230209B: Fermi GBM Observation
  9. IPN triangulation of GRB 230209B
  10. GRB 230204B: CALET Gamma-Ray Burst Monitor detection
  11. GRB 230204B: ATCA radio detection
  12. Outburst from LS V +44 17 / RX J0440.9+4431: Transient detection by GRBAlpha
  13. Fermi trigger No 697926015: Global MASTER-Net observations report
  14. Fermi trigger No 697904388: Global MASTER-Net observations report
  15. 230211A is not a GRB
  16. GRB 230211A: Fermi GBM Final Real-time Localization
  17. GRB 230209B: Swift/BAT-GUANO detection outside the coded FOV
  18. Fermi trigger No 697678542: Global MASTER-Net observations report
  19. Swift Trigger 1153670 is probably not a GRB
  20. GRB 230210A: Fermi GBM Final Real-time Localization
  21. Fermi GRB 230209B: Global MASTER-Net observations report
  22. GRB 230209B: Fermi GBM Final Real-time Localization
  23. GRB 230205A: 6 GHz VLA observations
  24. GRB 230209A is not a GRB
  25. GRB 230205A: SUBARU HSC pre-imaging for host galaxy search
  26. GRB 230209A: Fermi GBM Final Real-time Localization
  27. GRB 221009A: Continued Swift Observations
  28. Fermi Gamma-ray Burst Monitor trigger 230208382/697540213 is not a GRB
  29. GRB 230207B: Detection by GRBAlpha
  30. GRB 230205A: possible host galaxy detection with the Schmidt - Asiago telescope
  31. GRB 230204B: MASTER early OT detection
  32. GRB 230208A: Fermi GBM Final Real-time Localization
  33. Fermi Gamma-ray Burst Monitor triggers 230206723/697396830 and 230206797/697403223 are not GRBs
  34. GRB 230207B: Swift/BAT-GUANO detection outside the coded FOV
  35. ZTF23aabmzlp/AT2023azs: Neil Gehrels Swift Observatory X-ray observations
  36. GRB 230207B: AGILE detection of a burst
  37. Fermi GRB 230207A: Global MASTER-Net observations report
  38. GRB 230207A: Fermi GBM Final Real-time Localization
  39. GRB 230204B: LCOGT Optical Upper Limits
  40. GRB 230204B: Swift/UVOT Upper Limits
  41. Fermi trigger No 697403223: Global MASTER-Net observations report
  42. Fermi trigger No 697396830: Global MASTER-Net observations report
  43. GRB 230205A: Swift/UVOT Upper Limits
  44. GRB 230204B: Fermi GBM detection
  45. Fermi Gamma-ray Burst Monitor triggers due to recent activity of RX J0440.9+4431 (LS V +44 17)
  46. GRB 230205A: LCOGT Optical Upper Limits
  47. GRB 230204B: Swift-XRT afterglow detection
  48. GRB 230204B: 3.6m DOT optical observation
  49. GRB 230205A: SVOM/C-GFT optical upper limit
  50. GRB 230205A: OHP/T193 optical observations
  51. GRB 230204B: VLT/X-shooter redshift
  52. GRB 230205A: Swift-BAT refined analysis (T90 = 2.3 s)
  53. GRB 230204A: Swift-BAT refined analysis
  54. GRB 230204B: ATLAS detection of the optical afterglow and a projected location in a nearby galaxy group
  55. GRB 230205A: Swift-XRT refined Analysis
  56. GRB 230204B: Swift ToO observations
  57. GRB 230205A: Enhanced Swift-XRT position
  58. GRB 230205A: BOOTES-5/JGT early optical upper limit
  59. GRB 230204B: Detection by GRBAlpha
  60. GRB 230204B: AGILE detection
  61. GRB 230205A: Swift detection of a burst
  62. IceCube-230201A: BOOTES-4/MET Optical Upper Limits
  63. GRB 230204B: GIT discovery of the likely optical afterglow
  64. GRB 230204B: AstroSat CZTI detection
  65. GRB 230204B: Swift/BAT-GUANO detection outside the coded FOV
  66. GRB 230204A: Swift/UVOT Upper Limits
  67. GRB 230204B: MAXI/GSC detection
  68. GRB 230204A: Swift-XRT refined Analysis
  69. GRB 230204A/Swift J1552.8-5055: LCOGT Optical Counterpart Candidate
  70. Fermi trigger No 697208885: Global MASTER-Net observations report
  71. GRB 230204A: Enhanced Swift-XRT position
  72. GRB 230204A: Swift detection of a possible burst (or possible transient Swift J1552.8-5055)
  73. GRB 230201B: TURBO Optical Upper Limits
  74. Fermi Gamma-ray Burst Monitor trigger 230203275 / 697098930 is not a GRB
  75. Fermi trigger No 697098930: Global MASTER-Net observations report
  76. IceCube-230201A: Upper limits from a search for additional neutrino events in IceCube
  77. ZTF23aabmzlp/AT2023azs: Lulin 1m LOT optical observations
  78. GRB 221216A: Swift-BAT refined analysis
  79. ZTF23aabmzlp/AT2023azs: VLA radio detection
  80. ZTF23aaarlti/AT2023avj: AMI-LA radio detection
  81. ZTF23aabmzlp/AT2023azs: AMI-LA radio upper limit
  82. IceCube Alert 230201.26: Global MASTER-Net observations report
  83. Fermi GRB 230201B: Global MASTER-Net observations report
  84. Fermi-LAT gamma-ray observations of IceCube-230201A
  85. GRB 230201B: Fermi GBM Final Real-time Localization
  86. GRB 230126A: Detection by VZLUSAT-2
  87. Fermi GRB 230201A: Global MASTER-Net observations report
  88. IceCube-230201A - IceCube observation of a high-energy neutrino candidate track-like event
  89. GRB 221009A: radio afterglow detection with the EVN
  90. GRB 230201A: Fermi GBM Final Real-time Localization
  91. ZTF23aabmzlp/AT2023azs: LCOGT Optical Detection
  92. ZTF23aaarlti/AT2023avj: Assy continued optical observations
  93. ZTF23aabmzlp/AT2023azs: Mondy and AbAO optical observations
  94. AT2023avj: X-ray Detection with Swift/XRT
  95. ZTF23aabmzlp/AT2023azs: 1.3m DFOT optical observations
  96. GRB 230129A: AstroSat CZTI detection
  97. GRB 230128A: AstroSat CZTI detection
  98. GRB 230130A: Fermi GBM Final Real-time Localization
  99. ZTF23aaarlti/AT2023avj: VLA radio detection
  100. GRB 230129A: Fermi GBM Final Real-time Localization

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