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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"

19604 results found.

  1. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  2. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  3. GRB 250128B: VLA radio upper limit
  4. Ep250125A: 1.3m DFOT optical upper limit
  5. GRB 250129A: Skynet optical observations
  6. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  7. GRB 250129A: Swift-XRT refined Analysis
  8. GRB 250128B: TNG optical upper limit
  9. GRB 250129A: Swift/UVOT Detection
  10. GRB 250127A: CrAO and Terskol optical upper limits
  11. GRB 250129A: Enhanced Swift-XRT position
  12. GRB 250128B: NOT optical upper limit
  13. GRB 250129A: REM optical/NIR afterglow detection
  14. GRB 250129A: Early afterglow detection by LCO.
  15. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  16. GRB 250129A: LCO optical observations
  17. GRB 250129A: GOTO optical observations show brightening afterglow
  18. Swift GRB 250129A: Global MASTER-Net observations report
  19. GRB 250128B: Enhanced Swift-XRT position
  20. GRB 250129A: Swift detection of a burst with an optical counterpart
  21. Swift GRB 250129A: Global MASTER-Net OT detection
  22. GRB 250128B: Swift-XRT refined Analysis
  23. GRB 250128B: Fermi GBM Observation
  24. GRB 250128B: GOTO optical upper limit
  25. Swift GRB 250128B: Global MASTER-Net observations report
  26. EP250125a: Upper limits from Swift/BAT-GUANO
  27. GRB 250128B: LCO optical observations
  28. GRB 250128B: Swift detection of a short burst
  29. GRB 250127A: Swift-XRT observations
  30. GRB 250127A: EP-FXT afterglow detection
  31. GRB 250117A: Fermi GBM Observation
  32. GRB 250127A: SVOM/VT upper limit
  33. IPN triangulation of GRB 250119C
  34. GRB 250127A: Swift ToO observations
  35. GRB 250118A: Fermi GBM Observation
  36. EP250125a: REM optical counterpart detection
  37. GRB 250119C: Fermi GBM Observation
  38. EP250125a: Swift/XRT detection of a fading counterpart
  39. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  40. IPN triangulation of GRB 250118B
  41. Konus-Wind detection of GRB 250119B
  42. IPN triangulation of GRB 250119B
  43. Improved IPN triangulation of GRB 250107C
  44. GRB 250114A: Swift-BAT refined analysis
  45. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  46. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  47. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  48. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  49. Konus-Wind detection of GRB 250117A
  50. IPN triangulation of GRB 250117A (short)
  51. GRB 250117A: SVOM/GRM observation of a short burst
  52. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  53. Swift Trigger 1282245 is not a GRB
  54. GRB 250114B: Swift-XRT afterglow detection
  55. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  56. IPN triangulation of GRB 250113A
  57. GRB 250114B: Swift-XRT observations
  58. GRB 250114A: LCO optical counterpart detection.
  59. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  60. GRB 250114A: Swift-XRT refined Analysis
  61. GRB 250114A: LCOGT optical afterglow i-band detection
  62. GRB 250114B: Swift ToO observations
  63. EP250111a: SAO RAS optical upper limit
  64. GRB 250114A: Enhanced Swift-XRT position
  65. GRB 250114A: REM detection of the optical and NIR counterpart
  66. Swift GRB250114A: Global MASTER-Net OT detection
  67. GRB 250114A: LCO optical observations
  68. GRB 250114A: TRT optical observations
  69. Swift GRB 250114A: Global MASTER-Net observations report
  70. GRB 250114A: Swift detection of a burst with an optical counterpart
  71. GRB 250107A: VZLUSAT-2 detection
  72. GRB 250109A / EP250109a: GRBAlpha detection
  73. GRB 250106A: Swift-XRT afterglow detection
  74. GRB 250109A / EP250109a: Mephisto optical upper limits
  75. EP250111a: Swift/XRT detection and fading
  76. EP250108a / AT 2025kg: Swift UVOT detections
  77. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  78. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  79. GRB 250108A: Swift/XRT afterglow fading
  80. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  81. EP250109a: Swift/UVOT non-detection
  82. IPN triangulation of GRB 250107D (short/hard)
  83. IPN triangulation of GRB 250107C
  84. GRB 250108B: Swift-BAT refined analysis
  85. GRB 250108B: 1.3m DFOT upper limit
  86. GRB 250108B: REM optical/NIR upper limits
  87. EP250109a: GOTO optical upper limits
  88. EP250109a: Swift/XRT non-detection
  89. GRB 250108A: Swift/UVOT Upper Limits
  90. GRB 250108A: NOT optical upper limit
  91. GRB 250108B: Swift-XRT refined Analysis
  92. Swift GRB 250108B: Global MASTER-Net observations report
  93. GRB 250108A: Swift-XRT afterglow detection
  94. GRB 250108B: Swift/UVOT Upper Limits
  95. GRB 250103A: Swift-XRT afterglow detection
  96. GRB 250108B: Enhanced Swift-XRT position
  97. GRB 250108B: Swift detection of a burst
  98. GRB 250108A: Swift ToO observations
  99. GRB 250107A: Fermi GBM Observation
  100. GRB 241228B: Fermi-LAT detection

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