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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"

18403 results found.

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

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