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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 trigger No 726194053: Global MASTER-Net observations report
  2. GRB 240106A: Fermi GBM Final Real-time Localization
  3. IPN triangulation of GRB 240101C (short)
  4. GRB GRB240101C: Fermi GBM observation
  5. IceCube Alert 240105.52: Global MASTER-Net observations report
  6. GRB 240101A: 1.3m DFOT optical observations
  7. IceCube-240105A - IceCube observation of a high-energy neutrino candidate track-like event
  8. GRB 240102A: 1.3m DFOT optical upper limit
  9. GRB 240101B: 1.3m DFOT optical upper limit
  10. GRB 240101C: Swift/BAT-GUANO detection of a short burst
  11. LIGO/Virgo/KAGRA S240104bl: Updated Sky localization
  12. LIGO/Virgo/KAGRA S240104bl: Identification of a GW compact binary merger candidate
  13. GRB 240102C: AstroSat CZTI detection
  14. GRB 240101C: AstroSat CZTI detection
  15. GRB 231220A: Swift-UVOT upper limit
  16. GRB 240102A: Swift-BAT refined analysis
  17. GRB 240102A: Swift/UVOT Upper Limits
  18. GRB 231230A: Swift-BAT refined analysis
  19. GRB 240101A: Swift-BAT refined analysis
  20. GRB 240101B: Swift-BAT refined analysis
  21. GRB 240102A: Enhanced Swift-XRT position
  22. GRB 240101B: Swift-XRT refined Analysis
  23. GRB 240102A: Swift-XRT refined Analysis
  24. GRB 240102B (Fermi GBM trigger 725926335/240102925) is not a GRB
  25. GRB 240102A: LCOGT Optical Upper Limits
  26. Fermi trigger No 725857207: Global MASTER-Net observations report
  27. GRB240102A: BOOTES-6/DPRT optical upper limit
  28. GRB 240102B: Fermi GBM Final Real-time Localization
  29. GRB 240101B: MarSEC Observatory, Vicenza, Italy, UPPER LIMIT
  30. IceCube-Cascade 231230A: Upper limits from a search for additional neutrino events in IceCube
  31. GRB 240102A: Swift detection of a burst
  32. GRB 240101A: Terskol Zeiss-2000 optical observations
  33. GRB 240101C: GRBAlpha detection
  34. GRB 240101B: Swift/UVOT Upper Limits
  35. GRB 240101A: Swift/UVOT Upper Limits
  36. GRB 240101A: Swift-XRT refined Analysis
  37. GRB 240101B: Enhanced Swift-XRT position
  38. GRB 240101B: KAIT Optical Upper Limit
  39. GRB 240101A: KAIT Optical Upper Limit
  40. GRB 240101A: Enhanced Swift-XRT position
  41. GRB 240101C: Fermi GBM Final Localization
  42. Swift GRB240101.85: Global MASTER-Net observations report
  43. GRB 240101B: Swift detection of a burst
  44. GRB 240101A: Swift detection of a burst
  45. Fermi trigger No 725806648: Global MASTER-Net observations report
  46. LIGO/Virgo/KAGRA S231231ag: Updated Sky localization and Source Classification
  47. LIGO/Virgo/KAGRA S231231ag: Identification of a GW compact binary merger candidate
  48. GRB231230A: Fermi GBM Observation
  49. GRB 231230A: Swift-XRT refined Analysis
  50. GRB 231230A: GOTO optical upper limits
  51. GRB 231230A: Enhanced Swift-XRT position
  52. GRB 231230A: Swift/UVOT Upper Limits
  53. GRB 231230A: NOT optical upper limits
  54. Fermi trigger No 725592555: Global MASTER-Net observations report
  55. GRB 231230A: Prompt enhanced Swift-XRT position
  56. GRB 231230A: Swift detection of a burst
  57. Swift GRB231230.06: Global MASTER-Net observations report
  58. GRB 231230A: Fermi GBM Final Real-time Localization
  59. GRB 231210B: BOOTES-7 optical upper limit
  60. Swift Triggers 1205103, 1205104, 1205107 and 1205110 are not astrophysical events
  61. LIGO/Virgo/KAGRA S231224e: Upper limits from Swift/BAT-GUANO
  62. IPN triangulation of GRB 231224A (short)
  63. LIGO/Virgo/KAGRA S231226av: Updated Sky localization
  64. LIGO/Virgo/KAGRA S231226av: Identification of a GW compact binary merger candidate
  65. Fermi trigger No 725143760: Global MASTER-Net observations report
  66. GRB 231224A: Fermi GBM Final Real-time Localization
  67. GRB 231222B: GRBAlpha detection
  68. LIGO/Virgo/KAGRA S231224e: Updated Sky localization and Source Classification
  69. LIGO/Virgo/KAGRA S231224e: Identification of a GW compact binary merger candidate
  70. LIGO/Virgo/KAGRA S231223j: Updated Sky localization
  71. GRB 231222B: Swift-XRT afterglow detection
  72. LIGO/Virgo/KAGRA S231223j: Identification of a GW compact binary merger candidate
  73. Fermi trigger No 724921799: Global MASTER-Net observations report
  74. GRB 231222B: Fermi GBM Detection
  75. LAT GRB231222.31: Global MASTER-Net observations report
  76. GRB 231222B: Fermi-LAT detection
  77. GRB 231222A: Tiled Swift observations
  78. IceCube-231211A: GRANDMA observations of PKS2047+098
  79. GRID detection of GRB 231215A
  80. GRB 231222A: Fermi GBM Final Real-time Localization
  81. GRB 231220A: Swift-XRT follow-up observations
  82. GRB 231220A: Swift ToO observations
  83. GRB 231220A: Swift/BAT-GUANO arcminute localization of a long burst
  84. Fermi trigger No 724781422: Global MASTER-Net observations report
  85. GRB 231220A: Fermi GBM Final Real-time Localization
  86. GRB 231210B: new optical transient detected with the Greenhill Observatory University of Tasmania within the BAT-Swift enhanced position
  87. Fermi trigger No 724698747: Global MASTER-Net observations report
  88. GRB 231219A: Fermi GBM Final Real-time Localization
  89. GRID detection of GRB 231205B
  90. GRID detection of GRB 231205A
  91. GRB 231216A: GAD Observatory, La Spezia, Italy upper limit
  92. GRB 231214B: Fermi GBM observation
  93. GRB 231216A: optical upper limits from the INAF Asiago Observatory
  94. GRB 231216A: 10.4 m GTC optical upper limit
  95. GRB 231215A: AMI-LA radio detection
  96. GRB 231216A: Nanshan/HMT optical upper limit
  97. GRB 231216A: LCOGT Optical Upper Limits
  98. GRB 231216A: Osservatorio Astronomico Nastro Verde upper limit
  99. GRB 231216A: Swift-XRT refined analysis correction
  100. GRB 231215A: Osservatorio Astronomico Nastro Verde upper limit

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