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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"

18635 results found.

  1. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  2. GRB 250619B: Fermi GBM Observation
  3. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  4. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  5. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  6. GRB 250615A: Kilonova-Catcher optical upper limits
  7. GRB 250617B: Assy AZT-20 Optical Observations
  8. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  9. GRB 250615A/EP250615a: FTW optical and NIR observations
  10. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  11. GRB 250617B: Swift/UVOT Detection
  12. GRB 250617B: Kilonova-Catcher optical afterglow detection
  13. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  14. GRB 250617B: NOT NIR observations of the afterglow
  15. GRB 250617B: Swift-XRT refined Analysis
  16. GRB 250617B: SVOM/VT optical observation
  17. Swift GRB 250617B: Global MASTER-Net observations report
  18. GRB 250617B: GOTO optical upper limit
  19. GRB 250617B: Enhanced Swift-XRT position
  20. GRB 250617B: Fermi GBM Observation
  21. GRB 250615A: Swift-BAT refined analysis
  22. GRB 250617B: Fermi GBM Final Localization
  23. GRB 250617B: Ondrejov D50 optical afterglow detection
  24. GRB 250617B: Swift detection of a burst with an optical counterpart
  25. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  26. EP#01709178975: Swift-XRT counterpart detection
  27. Konus-Wind detection of GRB 250615A / EP250615a
  28. GRB 250615A / EP250615a: AstroSat CZTI detection
  29. GRB 250615A: COLIBRÍ optical upper limit
  30. GRB 250615A: DDOTI Optical Upper Limit
  31. GRB 250615A: Swift/UVOT Upper Limits
  32. GRB 250615A: Swift-XRT refined Analysis
  33. GRB 250615A: Enhanced Swift-XRT position
  34. GRB 250615A: Prompt enhanced Swift-XRT position
  35. GRB 250615A: Swift detection of a burst
  36. Swift GRB 250615A: Global MASTER-Net observations report
  37. sb25061207: Mephisto optical upper limits
  38. sb25061218: Swift-XRT observations
  39. sb25061207: EP-FXT follow-up observation and afterglow candidate
  40. sb25061207: Swift-XRT observations
  41. GRB 250610B: Swift-XRT refined Analysis
  42. EP250610a: continuous follow-up observations with EP-FXT
  43. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  44. Swift GRB250612.04: Global MASTER-Net observations report
  45. GRB 250610B: Swift/UVOT Detection
  46. EP250610A: Swift/UVOT Upper limits
  47. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  48. GRB 250610B: Swift-XRT counterpart detection
  49. GRB 250610B: SVOM/VT optical counterpart
  50. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  51. GRB 250605A: Swift-BAT refined analysis
  52. EP250610a: SVOM/VT optical upper limit
  53. EP250610a: REM optical/NIR observations
  54. GRB 250609A: Fermi GBM Observation
  55. EP250610a: Swift-XRT counterpart detection
  56. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  57. GRB 250605A: Swift/UVOT Upper Limits
  58. GRB 250527C: CrAO Optical Upper Limit
  59. GRB 250605A: SVOM/VT optical upper limit
  60. GRB 250605A: Swift-XRT refined Analysis
  61. GRB 250605A: Enhanced Swift-XRT position
  62. GRB 250605A: LT optical observations
  63. GRB 250605A: Swift detection of a burst
  64. Swift GRB250605.79: Global MASTER-Net observations report
  65. Konus-Wind detection of GRB 250601A
  66. IPN triangulation of GRB 250404B
  67. IPN triangulation of GRB 250529A
  68. GRB 250601A: PRIME H band upper limit.
  69. GRB 250601A: PRIME J band upper limit.
  70. GRB 250601A: VLT/FORS2 Optical Observation
  71. GRB 250601A: Fermi GBM Observation
  72. GRB 250603A: Swift/UVOT Upper Limits
  73. GRB 250603A: Swift-XRT refined Analysis
  74. GRB 250603A: Enhanced Swift-XRT position
  75. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  76. Swift GRB250603.05: Global MASTER-Net observations report
  77. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  78. GRB 250530C: Swift-BAT refined analysis
  79. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  80. GRB 250601A: Swift/XRT candidate afterglow
  81. GRB 250601A: Swift-XRT observations
  82. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  83. GRB 250601A: Swift ToO observations
  84. EP#01709177494: SVOM/VT optical observations
  85. EP#01709177494: Swift-XRT counterpart detection of known source
  86. GRB 250530C: BOOTES-7 optical upper limit
  87. GRB 250530C: Swift-XRT refined Analysis
  88. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  89. Swift GRB 250530C: Global MASTER-Net observations report
  90. GRB 250530C: Enhanced Swift-XRT position
  91. GRB 250530C: Swift detection of a burst
  92. GRB 250530A: EP-FXT counterpart detection
  93. GRB 250530A: SVOM/VT optical upper limit
  94. GRB 250530A: Swift-XRT counterpart detection
  95. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  96. GRB 250527C: Swift/UVOT Upper Limits
  97. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  98. GRB 250527B: Swift-XRT observations
  99. GRB 250520A: Swift-BAT refined analysis
  100. GRB 250527C: Swift ToO observations

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