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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. IPN triangulation of GRB 240101C (short)
  2. GRB GRB240101C: Fermi GBM observation
  3. IceCube Alert 240105.52: Global MASTER-Net observations report
  4. GRB 240101A: 1.3m DFOT optical observations
  5. IceCube-240105A - IceCube observation of a high-energy neutrino candidate track-like event
  6. GRB 240102A: 1.3m DFOT optical upper limit
  7. GRB 240101B: 1.3m DFOT optical upper limit
  8. GRB 240101C: Swift/BAT-GUANO detection of a short burst
  9. LIGO/Virgo/KAGRA S240104bl: Updated Sky localization
  10. LIGO/Virgo/KAGRA S240104bl: Identification of a GW compact binary merger candidate
  11. GRB 240102C: AstroSat CZTI detection
  12. GRB 240101C: AstroSat CZTI detection
  13. GRB 231220A: Swift-UVOT upper limit
  14. GRB 240102A: Swift-BAT refined analysis
  15. GRB 240102A: Swift/UVOT Upper Limits
  16. GRB 231230A: Swift-BAT refined analysis
  17. GRB 240101A: Swift-BAT refined analysis
  18. GRB 240101B: Swift-BAT refined analysis
  19. GRB 240102A: Enhanced Swift-XRT position
  20. GRB 240101B: Swift-XRT refined Analysis
  21. GRB 240102A: Swift-XRT refined Analysis
  22. GRB 240102B (Fermi GBM trigger 725926335/240102925) is not a GRB
  23. GRB 240102A: LCOGT Optical Upper Limits
  24. Fermi trigger No 725857207: Global MASTER-Net observations report
  25. GRB240102A: BOOTES-6/DPRT optical upper limit
  26. GRB 240102B: Fermi GBM Final Real-time Localization
  27. GRB 240101B: MarSEC Observatory, Vicenza, Italy, UPPER LIMIT
  28. IceCube-Cascade 231230A: Upper limits from a search for additional neutrino events in IceCube
  29. GRB 240102A: Swift detection of a burst
  30. GRB 240101A: Terskol Zeiss-2000 optical observations
  31. GRB 240101C: GRBAlpha detection
  32. GRB 240101B: Swift/UVOT Upper Limits
  33. GRB 240101A: Swift/UVOT Upper Limits
  34. GRB 240101A: Swift-XRT refined Analysis
  35. GRB 240101B: Enhanced Swift-XRT position
  36. GRB 240101B: KAIT Optical Upper Limit
  37. GRB 240101A: KAIT Optical Upper Limit
  38. GRB 240101A: Enhanced Swift-XRT position
  39. GRB 240101C: Fermi GBM Final Localization
  40. Swift GRB240101.85: Global MASTER-Net observations report
  41. GRB 240101B: Swift detection of a burst
  42. GRB 240101A: Swift detection of a burst
  43. Fermi trigger No 725806648: Global MASTER-Net observations report
  44. LIGO/Virgo/KAGRA S231231ag: Updated Sky localization and Source Classification
  45. LIGO/Virgo/KAGRA S231231ag: Identification of a GW compact binary merger candidate
  46. GRB231230A: Fermi GBM Observation
  47. GRB 231230A: Swift-XRT refined Analysis
  48. GRB 231230A: GOTO optical upper limits
  49. GRB 231230A: Enhanced Swift-XRT position
  50. GRB 231230A: Swift/UVOT Upper Limits
  51. GRB 231230A: NOT optical upper limits
  52. Fermi trigger No 725592555: Global MASTER-Net observations report
  53. GRB 231230A: Prompt enhanced Swift-XRT position
  54. GRB 231230A: Swift detection of a burst
  55. Swift GRB231230.06: Global MASTER-Net observations report
  56. GRB 231230A: Fermi GBM Final Real-time Localization
  57. GRB 231210B: BOOTES-7 optical upper limit
  58. Swift Triggers 1205103, 1205104, 1205107 and 1205110 are not astrophysical events
  59. LIGO/Virgo/KAGRA S231224e: Upper limits from Swift/BAT-GUANO
  60. IPN triangulation of GRB 231224A (short)
  61. LIGO/Virgo/KAGRA S231226av: Updated Sky localization
  62. LIGO/Virgo/KAGRA S231226av: Identification of a GW compact binary merger candidate
  63. Fermi trigger No 725143760: Global MASTER-Net observations report
  64. GRB 231224A: Fermi GBM Final Real-time Localization
  65. GRB 231222B: GRBAlpha detection
  66. LIGO/Virgo/KAGRA S231224e: Updated Sky localization and Source Classification
  67. LIGO/Virgo/KAGRA S231224e: Identification of a GW compact binary merger candidate
  68. LIGO/Virgo/KAGRA S231223j: Updated Sky localization
  69. GRB 231222B: Swift-XRT afterglow detection
  70. LIGO/Virgo/KAGRA S231223j: Identification of a GW compact binary merger candidate
  71. Fermi trigger No 724921799: Global MASTER-Net observations report
  72. GRB 231222B: Fermi GBM Detection
  73. LAT GRB231222.31: Global MASTER-Net observations report
  74. GRB 231222B: Fermi-LAT detection
  75. GRB 231222A: Tiled Swift observations
  76. IceCube-231211A: GRANDMA observations of PKS2047+098
  77. GRID detection of GRB 231215A
  78. GRB 231222A: Fermi GBM Final Real-time Localization
  79. GRB 231220A: Swift-XRT follow-up observations
  80. GRB 231220A: Swift ToO observations
  81. GRB 231220A: Swift/BAT-GUANO arcminute localization of a long burst
  82. Fermi trigger No 724781422: Global MASTER-Net observations report
  83. GRB 231220A: Fermi GBM Final Real-time Localization
  84. GRB 231210B: new optical transient detected with the Greenhill Observatory University of Tasmania within the BAT-Swift enhanced position
  85. Fermi trigger No 724698747: Global MASTER-Net observations report
  86. GRB 231219A: Fermi GBM Final Real-time Localization
  87. GRID detection of GRB 231205B
  88. GRID detection of GRB 231205A
  89. GRB 231216A: GAD Observatory, La Spezia, Italy upper limit
  90. GRB 231214B: Fermi GBM observation
  91. GRB 231216A: optical upper limits from the INAF Asiago Observatory
  92. GRB 231216A: 10.4 m GTC optical upper limit
  93. GRB 231215A: AMI-LA radio detection
  94. GRB 231216A: Nanshan/HMT optical upper limit
  95. GRB 231216A: LCOGT Optical Upper Limits
  96. GRB 231216A: Osservatorio Astronomico Nastro Verde upper limit
  97. GRB 231216A: Swift-XRT refined analysis correction
  98. GRB 231215A: Osservatorio Astronomico Nastro Verde upper limit
  99. GRB 231216A: Swift-XRT refined Analysis
  100. GRB 231216A: AST3-3 YaoAn Optical Upper Limit

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