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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"

18538 results found.

  1. GRB 250617B: Swift-BAT refined analysis
  2. IPN triangulation of GRB 250620С (long/bright)
  3. GRB 250620A: SVOM/GRM observation of a short burst
  4. GRB250620A: Fermi GBM Observation
  5. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  6. GRB 250619B: Fermi GBM Observation
  7. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  8. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  9. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  10. GRB 250615A: Kilonova-Catcher optical upper limits
  11. GRB 250617B: Assy AZT-20 Optical Observations
  12. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  13. GRB 250615A/EP250615a: FTW optical and NIR observations
  14. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  15. GRB 250617B: Swift/UVOT Detection
  16. GRB 250617B: Kilonova-Catcher optical afterglow detection
  17. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  18. GRB 250617B: NOT NIR observations of the afterglow
  19. GRB 250617B: Swift-XRT refined Analysis
  20. GRB 250617B: SVOM/VT optical observation
  21. Swift GRB 250617B: Global MASTER-Net observations report
  22. GRB 250617B: GOTO optical upper limit
  23. GRB 250617B: Enhanced Swift-XRT position
  24. GRB 250617B: Fermi GBM Observation
  25. GRB 250615A: Swift-BAT refined analysis
  26. GRB 250617B: Fermi GBM Final Localization
  27. GRB 250617B: Ondrejov D50 optical afterglow detection
  28. GRB 250617B: Swift detection of a burst with an optical counterpart
  29. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  30. EP#01709178975: Swift-XRT counterpart detection
  31. Konus-Wind detection of GRB 250615A / EP250615a
  32. GRB 250615A / EP250615a: AstroSat CZTI detection
  33. GRB 250615A: COLIBRÍ optical upper limit
  34. GRB 250615A: DDOTI Optical Upper Limit
  35. GRB 250615A: Swift/UVOT Upper Limits
  36. GRB 250615A: Swift-XRT refined Analysis
  37. GRB 250615A: Enhanced Swift-XRT position
  38. GRB 250615A: Prompt enhanced Swift-XRT position
  39. GRB 250615A: Swift detection of a burst
  40. Swift GRB250615.93: Global MASTER-Net observations report
  41. sb25061207: Mephisto optical upper limits
  42. sb25061218: Swift-XRT observations
  43. sb25061207: EP-FXT follow-up observation and afterglow candidate
  44. sb25061207: Swift-XRT observations
  45. GRB 250610B: Swift-XRT refined Analysis
  46. EP250610a: continuous follow-up observations with EP-FXT
  47. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  48. Swift GRB250612.04: Global MASTER-Net observations report
  49. GRB 250610B: Swift/UVOT Detection
  50. EP250610A: Swift/UVOT Upper limits
  51. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  52. GRB 250610B: Swift-XRT counterpart detection
  53. GRB 250610B: SVOM/VT optical counterpart
  54. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  55. GRB 250605A: Swift-BAT refined analysis
  56. EP250610a: SVOM/VT optical upper limit
  57. EP250610a: REM optical/NIR observations
  58. GRB 250609A: Fermi GBM Observation
  59. EP250610a: Swift-XRT counterpart detection
  60. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  61. GRB 250605A: Swift/UVOT Upper Limits
  62. GRB 250527C: CrAO Optical Upper Limit
  63. GRB 250605A: SVOM/VT optical upper limit
  64. GRB 250605A: Swift-XRT refined Analysis
  65. GRB 250605A: Enhanced Swift-XRT position
  66. GRB 250605A: LT optical observations
  67. GRB 250605A: Swift detection of a burst
  68. Swift GRB250605.79: Global MASTER-Net observations report
  69. Konus-Wind detection of GRB 250601A
  70. IPN triangulation of GRB 250404B
  71. IPN triangulation of GRB 250529A
  72. GRB 250601A: PRIME H band upper limit.
  73. GRB 250601A: PRIME J band upper limit.
  74. GRB 250601A: VLT/FORS2 Optical Observation
  75. GRB 250601A: Fermi GBM Observation
  76. GRB 250603A: Swift/UVOT Upper Limits
  77. GRB 250603A: Swift-XRT refined Analysis
  78. GRB 250603A: Enhanced Swift-XRT position
  79. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  80. Swift GRB250603.05: Global MASTER-Net observations report
  81. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  82. GRB 250530C: Swift-BAT refined analysis
  83. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  84. GRB 250601A: Swift/XRT candidate afterglow
  85. GRB 250601A: Swift-XRT observations
  86. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  87. GRB 250601A: Swift ToO observations
  88. EP#01709177494: SVOM/VT optical observations
  89. EP#01709177494: Swift-XRT counterpart detection of known source
  90. GRB 250530C: BOOTES-7 optical upper limit
  91. GRB 250530C: Swift-XRT refined Analysis
  92. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  93. Swift GRB 250530C: Global MASTER-Net observations report
  94. GRB 250530C: Enhanced Swift-XRT position
  95. GRB 250530C: Swift detection of a burst
  96. GRB 250530A: EP-FXT counterpart detection
  97. GRB 250530A: SVOM/VT optical upper limit
  98. GRB 250530A: Swift-XRT counterpart detection
  99. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  100. GRB 250527C: Swift/UVOT Upper Limits

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