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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"

18606 results found.

  1. GRB 250615A: COLIBRÍ optical upper limit
  2. GRB 250615A: DDOTI Optical Upper Limit
  3. GRB 250615A: Swift/UVOT Upper Limits
  4. GRB 250615A: Swift-XRT refined Analysis
  5. GRB 250615A: Enhanced Swift-XRT position
  6. GRB 250615A: Prompt enhanced Swift-XRT position
  7. GRB 250615A: Swift detection of a burst
  8. Swift GRB250615.93: Global MASTER-Net observations report
  9. sb25061207: Mephisto optical upper limits
  10. sb25061218: Swift-XRT observations
  11. sb25061207: EP-FXT follow-up observation and afterglow candidate
  12. sb25061207: Swift-XRT observations
  13. GRB 250610B: Swift-XRT refined Analysis
  14. EP250610a: continuous follow-up observations with EP-FXT
  15. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  16. Swift GRB250612.04: Global MASTER-Net observations report
  17. GRB 250610B: Swift/UVOT Detection
  18. EP250610A: Swift/UVOT Upper limits
  19. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  20. GRB 250610B: Swift-XRT counterpart detection
  21. GRB 250610B: SVOM/VT optical counterpart
  22. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  23. GRB 250605A: Swift-BAT refined analysis
  24. EP250610a: SVOM/VT optical upper limit
  25. EP250610a: REM optical/NIR observations
  26. GRB 250609A: Fermi GBM Observation
  27. EP250610a: Swift-XRT counterpart detection
  28. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  29. GRB 250605A: Swift/UVOT Upper Limits
  30. GRB 250527C: CrAO Optical Upper Limit
  31. GRB 250605A: SVOM/VT optical upper limit
  32. GRB 250605A: Swift-XRT refined Analysis
  33. GRB 250605A: Enhanced Swift-XRT position
  34. GRB 250605A: LT optical observations
  35. GRB 250605A: Swift detection of a burst
  36. Swift GRB250605.79: Global MASTER-Net observations report
  37. Konus-Wind detection of GRB 250601A
  38. IPN triangulation of GRB 250404B
  39. IPN triangulation of GRB 250529A
  40. GRB 250601A: PRIME H band upper limit.
  41. GRB 250601A: PRIME J band upper limit.
  42. GRB 250601A: VLT/FORS2 Optical Observation
  43. GRB 250601A: Fermi GBM Observation
  44. GRB 250603A: Swift/UVOT Upper Limits
  45. GRB 250603A: Swift-XRT refined Analysis
  46. GRB 250603A: Enhanced Swift-XRT position
  47. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  48. Swift GRB250603.05: Global MASTER-Net observations report
  49. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  50. GRB 250530C: Swift-BAT refined analysis
  51. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  52. GRB 250601A: Swift/XRT candidate afterglow
  53. GRB 250601A: Swift-XRT observations
  54. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  55. GRB 250601A: Swift ToO observations
  56. EP#01709177494: SVOM/VT optical observations
  57. EP#01709177494: Swift-XRT counterpart detection of known source
  58. GRB 250530C: BOOTES-7 optical upper limit
  59. GRB 250530C: Swift-XRT refined Analysis
  60. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  61. Swift GRB 250530C: Global MASTER-Net observations report
  62. GRB 250530C: Enhanced Swift-XRT position
  63. GRB 250530C: Swift detection of a burst
  64. GRB 250530A: EP-FXT counterpart detection
  65. GRB 250530A: SVOM/VT optical upper limit
  66. GRB 250530A: Swift-XRT counterpart detection
  67. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  68. GRB 250527C: Swift/UVOT Upper Limits
  69. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  70. GRB 250527B: Swift-XRT observations
  71. GRB 250520A: Swift-BAT refined analysis
  72. GRB 250527C: Swift ToO observations
  73. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  74. GRB 250527B: Tiled Swift observations
  75. GRB 250520A: GRBAlpha detection
  76. GRB 250521B: SVOM/VT optical upper limit
  77. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  78. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  79. EP#01709176612: Swift-XRT counterpart detection of flaring star
  80. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  81. GRB 250521B: Swift ToO observations
  82. Konus-Wind detection of GRB 250520A (short/hard)
  83. GRB 250520A: Swift/UVOT Upper Limits
  84. IPN triangulation of GRB 250516B
  85. GRB 250520A: J-band observations with WINTER
  86. GRB 250520A: Swift-XRT refined Analysis
  87. GRB 250520A: REM optical/NIR early observations
  88. GRB 250520A:SVOM/VT optical candidate
  89. GRB 250520A: COLIBRÍ optical upper limit
  90. GRB 250520A: DDOTI Optical Upper Limit
  91. GRB 250520A: AstroSat CZTI detection of a short burst
  92. GRB 250520A: SVOM/GRM observation
  93. GRB 250520A: Enhanced Swift-XRT position
  94. GRB 250520A: GOTO optical upper limit
  95. GRB 250520A: Prompt enhanced Swift-XRT position
  96. GRB 250520A: Swift detection of a burst
  97. Swift GRB 250520A: Global MASTER-Net observations report
  98. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  99. GRB 250516A: Swift-BAT refined analysis
  100. Konus-Wind detection of GRB 250516A

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