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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"

18631 results found.

  1. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  2. GRB 250615A: Kilonova-Catcher optical upper limits
  3. GRB 250617B: Assy AZT-20 Optical Observations
  4. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  5. GRB 250615A/EP250615a: FTW optical and NIR observations
  6. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  7. GRB 250617B: Swift/UVOT Detection
  8. GRB 250617B: Kilonova-Catcher optical afterglow detection
  9. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  10. GRB 250617B: NOT NIR observations of the afterglow
  11. GRB 250617B: Swift-XRT refined Analysis
  12. GRB 250617B: SVOM/VT optical observation
  13. Swift GRB 250617B: Global MASTER-Net observations report
  14. GRB 250617B: GOTO optical upper limit
  15. GRB 250617B: Enhanced Swift-XRT position
  16. GRB 250617B: Fermi GBM Observation
  17. GRB 250615A: Swift-BAT refined analysis
  18. GRB 250617B: Fermi GBM Final Localization
  19. GRB 250617B: Ondrejov D50 optical afterglow detection
  20. GRB 250617B: Swift detection of a burst with an optical counterpart
  21. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  22. EP#01709178975: Swift-XRT counterpart detection
  23. Konus-Wind detection of GRB 250615A / EP250615a
  24. GRB 250615A / EP250615a: AstroSat CZTI detection
  25. GRB 250615A: COLIBRÍ optical upper limit
  26. GRB 250615A: DDOTI Optical Upper Limit
  27. GRB 250615A: Swift/UVOT Upper Limits
  28. GRB 250615A: Swift-XRT refined Analysis
  29. GRB 250615A: Enhanced Swift-XRT position
  30. GRB 250615A: Prompt enhanced Swift-XRT position
  31. GRB 250615A: Swift detection of a burst
  32. Swift GRB250615.93: Global MASTER-Net observations report
  33. sb25061207: Mephisto optical upper limits
  34. sb25061218: Swift-XRT observations
  35. sb25061207: EP-FXT follow-up observation and afterglow candidate
  36. sb25061207: Swift-XRT observations
  37. GRB 250610B: Swift-XRT refined Analysis
  38. EP250610a: continuous follow-up observations with EP-FXT
  39. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  40. Swift GRB250612.04: Global MASTER-Net observations report
  41. GRB 250610B: Swift/UVOT Detection
  42. EP250610A: Swift/UVOT Upper limits
  43. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  44. GRB 250610B: Swift-XRT counterpart detection
  45. GRB 250610B: SVOM/VT optical counterpart
  46. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  47. GRB 250605A: Swift-BAT refined analysis
  48. EP250610a: SVOM/VT optical upper limit
  49. EP250610a: REM optical/NIR observations
  50. GRB 250609A: Fermi GBM Observation
  51. EP250610a: Swift-XRT counterpart detection
  52. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  53. GRB 250605A: Swift/UVOT Upper Limits
  54. GRB 250527C: CrAO Optical Upper Limit
  55. GRB 250605A: SVOM/VT optical upper limit
  56. GRB 250605A: Swift-XRT refined Analysis
  57. GRB 250605A: Enhanced Swift-XRT position
  58. GRB 250605A: LT optical observations
  59. GRB 250605A: Swift detection of a burst
  60. Swift GRB250605.79: Global MASTER-Net observations report
  61. Konus-Wind detection of GRB 250601A
  62. IPN triangulation of GRB 250404B
  63. IPN triangulation of GRB 250529A
  64. GRB 250601A: PRIME H band upper limit.
  65. GRB 250601A: PRIME J band upper limit.
  66. GRB 250601A: VLT/FORS2 Optical Observation
  67. GRB 250601A: Fermi GBM Observation
  68. GRB 250603A: Swift/UVOT Upper Limits
  69. GRB 250603A: Swift-XRT refined Analysis
  70. GRB 250603A: Enhanced Swift-XRT position
  71. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  72. Swift GRB250603.05: Global MASTER-Net observations report
  73. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  74. GRB 250530C: Swift-BAT refined analysis
  75. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  76. GRB 250601A: Swift/XRT candidate afterglow
  77. GRB 250601A: Swift-XRT observations
  78. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  79. GRB 250601A: Swift ToO observations
  80. EP#01709177494: SVOM/VT optical observations
  81. EP#01709177494: Swift-XRT counterpart detection of known source
  82. GRB 250530C: BOOTES-7 optical upper limit
  83. GRB 250530C: Swift-XRT refined Analysis
  84. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  85. Swift GRB 250530C: Global MASTER-Net observations report
  86. GRB 250530C: Enhanced Swift-XRT position
  87. GRB 250530C: Swift detection of a burst
  88. GRB 250530A: EP-FXT counterpart detection
  89. GRB 250530A: SVOM/VT optical upper limit
  90. GRB 250530A: Swift-XRT counterpart detection
  91. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  92. GRB 250527C: Swift/UVOT Upper Limits
  93. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  94. GRB 250527B: Swift-XRT observations
  95. GRB 250520A: Swift-BAT refined analysis
  96. GRB 250527C: Swift ToO observations
  97. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  98. GRB 250527B: Tiled Swift observations
  99. GRB 250520A: GRBAlpha detection
  100. GRB 250521B: SVOM/VT optical upper limit

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