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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"

19592 results found.

  1. GRB 250128B: Enhanced Swift-XRT position
  2. GRB 250129A: Swift detection of a burst with an optical counterpart
  3. Swift GRB 250129A: Global MASTER-Net OT detection
  4. GRB 250128B: Swift-XRT refined Analysis
  5. GRB 250128B: Fermi GBM Observation
  6. GRB 250128B: GOTO optical upper limit
  7. Swift GRB 250128B: Global MASTER-Net observations report
  8. EP250125a: Upper limits from Swift/BAT-GUANO
  9. GRB 250128B: LCO optical observations
  10. GRB 250128B: Swift detection of a short burst
  11. GRB 250127A: Swift-XRT observations
  12. GRB 250127A: EP-FXT afterglow detection
  13. GRB 250117A: Fermi GBM Observation
  14. GRB 250127A: SVOM/VT upper limit
  15. IPN triangulation of GRB 250119C
  16. GRB 250127A: Swift ToO observations
  17. GRB 250118A: Fermi GBM Observation
  18. EP250125a: REM optical counterpart detection
  19. GRB 250119C: Fermi GBM Observation
  20. EP250125a: Swift/XRT detection of a fading counterpart
  21. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  22. IPN triangulation of GRB 250118B
  23. Konus-Wind detection of GRB 250119B
  24. IPN triangulation of GRB 250119B
  25. Improved IPN triangulation of GRB 250107C
  26. GRB 250114A: Swift-BAT refined analysis
  27. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  28. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  29. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  30. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  31. Konus-Wind detection of GRB 250117A
  32. IPN triangulation of GRB 250117A (short)
  33. GRB 250117A: SVOM/GRM observation of a short burst
  34. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  35. Swift Trigger 1282245 is not a GRB
  36. GRB 250114B: Swift-XRT afterglow detection
  37. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  38. IPN triangulation of GRB 250113A
  39. GRB 250114B: Swift-XRT observations
  40. GRB 250114A: LCO optical counterpart detection.
  41. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  42. GRB 250114A: Swift-XRT refined Analysis
  43. GRB 250114A: LCOGT optical afterglow i-band detection
  44. GRB 250114B: Swift ToO observations
  45. EP250111a: SAO RAS optical upper limit
  46. GRB 250114A: Enhanced Swift-XRT position
  47. GRB 250114A: REM detection of the optical and NIR counterpart
  48. Swift GRB250114A: Global MASTER-Net OT detection
  49. GRB 250114A: LCO optical observations
  50. GRB 250114A: TRT optical observations
  51. Swift GRB 250114A: Global MASTER-Net observations report
  52. GRB 250114A: Swift detection of a burst with an optical counterpart
  53. GRB 250107A: VZLUSAT-2 detection
  54. GRB 250109A / EP250109a: GRBAlpha detection
  55. GRB 250106A: Swift-XRT afterglow detection
  56. GRB 250109A / EP250109a: Mephisto optical upper limits
  57. EP250111a: Swift/XRT detection and fading
  58. EP250108a / AT 2025kg: Swift UVOT detections
  59. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  60. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  61. GRB 250108A: Swift/XRT afterglow fading
  62. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  63. EP250109a: Swift/UVOT non-detection
  64. IPN triangulation of GRB 250107D (short/hard)
  65. IPN triangulation of GRB 250107C
  66. GRB 250108B: Swift-BAT refined analysis
  67. GRB 250108B: 1.3m DFOT upper limit
  68. GRB 250108B: REM optical/NIR upper limits
  69. EP250109a: GOTO optical upper limits
  70. EP250109a: Swift/XRT non-detection
  71. GRB 250108A: Swift/UVOT Upper Limits
  72. GRB 250108A: NOT optical upper limit
  73. GRB 250108B: Swift-XRT refined Analysis
  74. Swift GRB 250108B: Global MASTER-Net observations report
  75. GRB 250108A: Swift-XRT afterglow detection
  76. GRB 250108B: Swift/UVOT Upper Limits
  77. GRB 250103A: Swift-XRT afterglow detection
  78. GRB 250108B: Enhanced Swift-XRT position
  79. GRB 250108B: Swift detection of a burst
  80. GRB 250108A: Swift ToO observations
  81. GRB 250107A: Fermi GBM Observation
  82. GRB 241228B: Fermi-LAT detection
  83. GRB 250107A: Swift ToO observations
  84. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  85. GRB 250106A: NOT optical observations
  86. GRB 250103B: REM optical/NIR upper limits
  87. GRB 250101A: REM optical/NIR counterpart detection
  88. GRB 250106A: Swift-XRT observations
  89. GRB 250106A: Swift ToO observations
  90. GRB 241229A: SVOM/VT optical upperlimit
  91. GRB 250103B: Swift-XRT refined Analysis
  92. GRB 250103B: LCO/1m optical afterglow candidate detection
  93. GRB 250103A: Swift-XRT observations
  94. GRB 250101A: 1.3m DFOT optical afterglow detection
  95. GRB 241229A: 1.3m DFOT upper limit
  96. GRB 241228A: 1.3m DFOT upper limit
  97. GRB 250103B:SVOM/VT optical counterpart
  98. GRB 250101A: further LCOGT optical afterglow observations
  99. GRB 250103B: LCOGT Optical Upper Limit
  100. Swift GRB 250103B: Global MASTER-Net observations report

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