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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"

26038 results found.

  1. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  2. GRB 250207A: Swift detection of a burst with optical counterpart
  3. GRB 250205A: Fermi GBM Observation
  4. GRB 250205A: REM NIR upper limit
  5. GRB 250205A: Swift/UVOT Upper Limits
  6. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  7. GRB 250205A: Swift/XRT detection
  8. GRB250205A: SVOM/VT optical afterglow detection
  9. IPN triangulation of GRB 250201A
  10. GRB 250129A: Swift-BAT refined analysis
  11. IPN triangulation of GRB 250204B (short/hard)
  12. IPN triangulation of GRB 250202B
  13. GRB 250129A: LCO late afterglow detection
  14. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  15. GRB 250129a: Liverpool Telescope optical follow-up
  16. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  17. GRB 250129A: SVOM/C-GFT optical observations
  18. Swift GRB250129A: MASTER 4 days observations report
  19. Konus-Wind detection of GRB 250129A
  20. GRB 250129A: 1.3m DFOT Optical observations
  21. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  22. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  23. GRB 250129A: optical photometry from Konkoly
  24. GRB 250129A: COLIBRÍ Optical Observations
  25. GRB 250128B: VLA possible radio detection
  26. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
  27. GRB 250129A: iTelescope optical observation
  28. GRB 250129A: NOT optical observations of continuining activity
  29. GRB 250129a: Liverpool Telescope optical follow-up
  30. GRB 250129A: TNG NIR afterglow detection
  31. GRB 250129A: AKO Optical Afterglow Detection
  32. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  33. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  34. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  35. GRB 250128B: VLA radio upper limit
  36. Ep250125A: 1.3m DFOT optical upper limit
  37. GRB 250129A: Skynet optical observations
  38. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  39. GRB 250129A: Swift-XRT refined Analysis
  40. GRB 250128B: Gemini-North optical extended source detection
  41. GRB 250128B: TNG optical upper limit
  42. GRB 250129A: Swift/UVOT Detection
  43. GRB 250128B: VLT/HAWKI near-infrared observations
  44. GRB 250127A: CrAO and Terskol optical upper limits
  45. GRB 250129A: Enhanced Swift-XRT position
  46. GRB 250128B: NOT optical upper limit
  47. GRB 250128B: VLT/FORS2 optical observations
  48. GRB 250129A: REM optical/NIR afterglow detection
  49. GRB 250129A: OHP/T193 optical and spectroscopy observations
  50. GRB 250129A: Early afterglow detection by LCO.
  51. GRB 250128B: OHP/T193 optical upper limit
  52. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  53. GRB 250129A: LCO optical observations
  54. GRB 250129A: GOTO optical observations show brightening afterglow
  55. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  56. Swift GRB 250129A: Global MASTER-Net observations report
  57. GRB 250128B: Enhanced Swift-XRT position
  58. GRB 250129A: Swift detection of a burst with an optical counterpart
  59. Swift GRB 250129A: Global MASTER-Net OT detection
  60. GRB 250128B: Swift-XRT refined Analysis
  61. GRB 250128B: Fermi GBM Observation
  62. GRB 250128B: GOTO optical upper limit
  63. Swift GRB 250128B: Global MASTER-Net observations report
  64. EP250125a: Upper limits from Swift/BAT-GUANO
  65. GRB 250128B: LCO optical observations
  66. GRB 250128B: Swift detection of a short burst
  67. GRB 250127A: Swift-XRT observations
  68. GRB 250127B: DDOTI Upper Limit on the Afterglow
  69. GRB 250127A: EP-FXT afterglow detection
  70. GRB 250117A: Fermi GBM Observation
  71. GRB 250127A: SVOM/VT upper limit
  72. IPN triangulation of GRB 250119C
  73. GRB 250127A: Swift ToO observations
  74. GRB 250118A: Fermi GBM Observation
  75. EP250125a: REM optical counterpart detection
  76. GRB 250119C: Fermi GBM Observation
  77. EP250125a: Swift/XRT detection of a fading counterpart
  78. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  79. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  80. IPN triangulation of GRB 250118B
  81. Konus-Wind detection of GRB 250119B
  82. IPN triangulation of GRB 250119B
  83. Improved IPN triangulation of GRB 250107C
  84. GRB 250114A: Swift-BAT refined analysis
  85. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  86. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  87. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  88. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  89. Konus-Wind detection of GRB 250117A
  90. IPN triangulation of GRB 250117A (short)
  91. ATCA detection of possible radio counterpart to GRB 250114A
  92. GRB 250117A: SVOM/GRM observation of a short burst
  93. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  94. EP250108a / AT2025kg: VLA radio upper limit
  95. Swift Trigger 1282245 is not a GRB
  96. GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
  97. GRB 250114B: Swift-XRT afterglow detection
  98. GRB 250114B: SVOM/VT upper limit
  99. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  100. IPN triangulation of GRB 250113A

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