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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"

18825 results found.

  1. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  2. GRB 250617B: Swift/UVOT Detection
  3. GRB 250617B: Kilonova-Catcher optical afterglow detection
  4. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  5. GRB 250617B: NOT NIR observations of the afterglow
  6. GRB 250617B: Swift-XRT refined Analysis
  7. GRB 250617B: SVOM/VT optical observation
  8. Swift GRB 250617B: Global MASTER-Net observations report
  9. GRB 250617B: GOTO optical upper limit
  10. GRB 250617B: Enhanced Swift-XRT position
  11. GRB 250617B: Fermi GBM Observation
  12. GRB 250615A: Swift-BAT refined analysis
  13. GRB 250617B: Fermi GBM Final Localization
  14. GRB 250617B: Ondrejov D50 optical afterglow detection
  15. GRB 250617B: Swift detection of a burst with an optical counterpart
  16. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  17. EP#01709178975: Swift-XRT counterpart detection
  18. Konus-Wind detection of GRB 250615A / EP250615a
  19. GRB 250615A / EP250615a: AstroSat CZTI detection
  20. GRB 250615A: COLIBRÍ optical upper limit
  21. GRB 250615A: DDOTI Optical Upper Limit
  22. GRB 250615A: Swift/UVOT Upper Limits
  23. GRB 250615A: Swift-XRT refined Analysis
  24. GRB 250615A: Enhanced Swift-XRT position
  25. GRB 250615A: Prompt enhanced Swift-XRT position
  26. GRB 250615A: Swift detection of a burst
  27. Swift GRB 250615A: Global MASTER-Net observations report
  28. sb25061207: Mephisto optical upper limits
  29. sb25061218: Swift-XRT observations
  30. sb25061207: EP-FXT follow-up observation and afterglow candidate
  31. sb25061207: Swift-XRT observations
  32. GRB 250610B: Swift-XRT refined Analysis
  33. EP250610a: continuous follow-up observations with EP-FXT
  34. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  35. Swift GRB250612.04: Global MASTER-Net observations report
  36. GRB 250610B: Swift/UVOT Detection
  37. EP250610A: Swift/UVOT Upper limits
  38. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  39. GRB 250610B: Swift-XRT counterpart detection
  40. GRB 250610B: SVOM/VT optical counterpart
  41. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  42. GRB 250605A: Swift-BAT refined analysis
  43. EP250610a: SVOM/VT optical upper limit
  44. EP250610a: REM optical/NIR observations
  45. GRB 250609A: Fermi GBM Observation
  46. EP250610a: Swift-XRT counterpart detection
  47. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  48. GRB 250605A: Swift/UVOT Upper Limits
  49. GRB 250527C: CrAO Optical Upper Limit
  50. GRB 250605A: SVOM/VT optical upper limit
  51. GRB 250605A: Swift-XRT refined Analysis
  52. GRB 250605A: Enhanced Swift-XRT position
  53. GRB 250605A: LT optical observations
  54. GRB 250605A: Swift detection of a burst
  55. Swift GRB250605.79: Global MASTER-Net observations report
  56. Konus-Wind detection of GRB 250601A
  57. IPN triangulation of GRB 250404B
  58. IPN triangulation of GRB 250529A
  59. GRB 250601A: PRIME H band upper limit.
  60. GRB 250601A: PRIME J band upper limit.
  61. GRB 250601A: VLT/FORS2 Optical Observation
  62. GRB 250601A: Fermi GBM Observation
  63. GRB 250603A: Swift/UVOT Upper Limits
  64. GRB 250603A: Swift-XRT refined Analysis
  65. GRB 250603A: Enhanced Swift-XRT position
  66. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  67. Swift GRB250603.05: Global MASTER-Net observations report
  68. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  69. GRB 250530C: Swift-BAT refined analysis
  70. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  71. GRB 250601A: Swift/XRT candidate afterglow
  72. GRB 250601A: Swift-XRT observations
  73. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  74. GRB 250601A: Swift ToO observations
  75. EP#01709177494: SVOM/VT optical observations
  76. EP#01709177494: Swift-XRT counterpart detection of known source
  77. GRB 250530C: BOOTES-7 optical upper limit
  78. GRB 250530C: Swift-XRT refined Analysis
  79. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  80. Swift GRB 250530C: Global MASTER-Net observations report
  81. GRB 250530C: Enhanced Swift-XRT position
  82. GRB 250530C: Swift detection of a burst
  83. GRB 250530A: EP-FXT counterpart detection
  84. GRB 250530A: SVOM/VT optical upper limit
  85. GRB 250530A: Swift-XRT counterpart detection
  86. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  87. GRB 250527C: Swift/UVOT Upper Limits
  88. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  89. GRB 250527B: Swift-XRT observations
  90. GRB 250520A: Swift-BAT refined analysis
  91. GRB 250527C: Swift ToO observations
  92. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  93. GRB 250527B: Tiled Swift observations
  94. GRB 250520A: GRBAlpha detection
  95. GRB 250521B: SVOM/VT optical upper limit
  96. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  97. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  98. EP#01709176612: Swift-XRT counterpart detection of flaring star
  99. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  100. GRB 250521B: Swift ToO observations

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