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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"

18651 results found.

  1. GRB 250625A: ABObservatory afterglow detection
  2. GRB 250625A: COLIBRÍ optical observations
  3. GRB 250625A: Fermi-LAT detection
  4. GRB 250625A: Swift-XRT refined Analysis
  5. GRB 250625A: JinShan optical observations
  6. GRB250625A: Fermi GBM Observation
  7. Swift GRB 250625A: Global MASTER-Net observations report
  8. GRB 250625A: SVOM/VT optical confirmation
  9. GRB 250620B: Fermi GBM Observation
  10. GRB 250625A: Enhanced Swift-XRT position
  11. GRB 250625A: Swift detection of a burst
  12. GRB 250620A: AstroSat CZTI detection
  13. GRB 241018A: Maidanak optical observations
  14. GRB 250617B: Swift-BAT refined analysis
  15. IPN triangulation of GRB 250620С (long/bright)
  16. GRB 250620A: SVOM/GRM observation of a short burst
  17. GRB250620A: Fermi GBM Observation
  18. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  19. GRB 250619B: Fermi GBM Observation
  20. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  21. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  22. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  23. GRB 250615A: Kilonova-Catcher optical upper limits
  24. GRB 250617B: Assy AZT-20 Optical Observations
  25. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  26. GRB 250615A/EP250615a: FTW optical and NIR observations
  27. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  28. GRB 250617B: Swift/UVOT Detection
  29. GRB 250617B: Kilonova-Catcher optical afterglow detection
  30. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  31. GRB 250617B: NOT NIR observations of the afterglow
  32. GRB 250617B: Swift-XRT refined Analysis
  33. GRB 250617B: SVOM/VT optical observation
  34. Swift GRB 250617B: Global MASTER-Net observations report
  35. GRB 250617B: GOTO optical upper limit
  36. GRB 250617B: Enhanced Swift-XRT position
  37. GRB 250617B: Fermi GBM Observation
  38. GRB 250615A: Swift-BAT refined analysis
  39. GRB 250617B: Fermi GBM Final Localization
  40. GRB 250617B: Ondrejov D50 optical afterglow detection
  41. GRB 250617B: Swift detection of a burst with an optical counterpart
  42. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  43. EP#01709178975: Swift-XRT counterpart detection
  44. Konus-Wind detection of GRB 250615A / EP250615a
  45. GRB 250615A / EP250615a: AstroSat CZTI detection
  46. GRB 250615A: COLIBRÍ optical upper limit
  47. GRB 250615A: DDOTI Optical Upper Limit
  48. GRB 250615A: Swift/UVOT Upper Limits
  49. GRB 250615A: Swift-XRT refined Analysis
  50. GRB 250615A: Enhanced Swift-XRT position
  51. GRB 250615A: Prompt enhanced Swift-XRT position
  52. GRB 250615A: Swift detection of a burst
  53. Swift GRB 250615A: Global MASTER-Net observations report
  54. sb25061207: Mephisto optical upper limits
  55. sb25061218: Swift-XRT observations
  56. sb25061207: EP-FXT follow-up observation and afterglow candidate
  57. sb25061207: Swift-XRT observations
  58. GRB 250610B: Swift-XRT refined Analysis
  59. EP250610a: continuous follow-up observations with EP-FXT
  60. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  61. Swift GRB250612.04: Global MASTER-Net observations report
  62. GRB 250610B: Swift/UVOT Detection
  63. EP250610A: Swift/UVOT Upper limits
  64. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  65. GRB 250610B: Swift-XRT counterpart detection
  66. GRB 250610B: SVOM/VT optical counterpart
  67. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  68. GRB 250605A: Swift-BAT refined analysis
  69. EP250610a: SVOM/VT optical upper limit
  70. EP250610a: REM optical/NIR observations
  71. GRB 250609A: Fermi GBM Observation
  72. EP250610a: Swift-XRT counterpart detection
  73. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  74. GRB 250605A: Swift/UVOT Upper Limits
  75. GRB 250527C: CrAO Optical Upper Limit
  76. GRB 250605A: SVOM/VT optical upper limit
  77. GRB 250605A: Swift-XRT refined Analysis
  78. GRB 250605A: Enhanced Swift-XRT position
  79. GRB 250605A: LT optical observations
  80. GRB 250605A: Swift detection of a burst
  81. Swift GRB250605.79: Global MASTER-Net observations report
  82. Konus-Wind detection of GRB 250601A
  83. IPN triangulation of GRB 250404B
  84. IPN triangulation of GRB 250529A
  85. GRB 250601A: PRIME H band upper limit.
  86. GRB 250601A: PRIME J band upper limit.
  87. GRB 250601A: VLT/FORS2 Optical Observation
  88. GRB 250601A: Fermi GBM Observation
  89. GRB 250603A: Swift/UVOT Upper Limits
  90. GRB 250603A: Swift-XRT refined Analysis
  91. GRB 250603A: Enhanced Swift-XRT position
  92. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  93. Swift GRB250603.05: Global MASTER-Net observations report
  94. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  95. GRB 250530C: Swift-BAT refined analysis
  96. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  97. GRB 250601A: Swift/XRT candidate afterglow
  98. GRB 250601A: Swift-XRT observations
  99. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  100. GRB 250601A: Swift ToO observations

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