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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').
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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

16195 results found.

  1. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  2. GRB 250419A: SVOM detection of a soft burst
  3. EP250416a: refined EP-WXT and EP-FXT analysis
  4. EP20250416a: Swift/XRT counterpart detection
  5. IceCube-250416A: DDOTI Optical Observations
  6. EP250416a: Gemini South-GMOS optical counterpart
  7. SVOM/sb25041603 is not a GRB
  8. EP250416a: Einstein Probe detection of an X-ray transient
  9. IceCube-250416A: Global MASTER-Net observations report
  10. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  11. IceCube 250414.324: DDOTI Optical Observations
  12. EP250304a: ATCA radio observations
  13. EP250404a: Nanshan 0.43m Telescope optical observatios
  14. GRB 250411A: DDOTI Optical Observations
  15. GRB 250314A: e-MERLIN observations
  16. GRB 250407A: Mondy and AbAO Optical Observations
  17. EP250227a: Further NOT optical observations
  18. IceCube-250406A: Swift-XRT observations
  19. GRB 250407A: LCO detection of a fading optical counterpart
  20. GRB 250407A: SVOM/GRM observation of a bright long burst
  21. GRB 250407A: EP-WXT afterglow detection
  22. EP250407a: EP-WXT detection of a fast X-ray transient
  23. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  24. GRB 250407A: KAIT Optical Afterglow Candidate
  25. IceCube-250406A: No candidates from the Zwicky Transient Facility
  26. GRB 250407A: Swift-XRT afterglow detection
  27. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  28. IPN triangulation of GRB 250406B (short/hard)
  29. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  30. IceCube 250406.951: DDOTI Optical Observations
  31. IceCube Alert 250406.95: Global MASTER-Net observations report
  32. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  33. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  34. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  35. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  36. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  37. Konus-Wind detection of GRB 250404A / EP250404a
  38. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  39. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  40. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  41. EP250402a: Optical upper limit with PD 1.3m observations
  42. GRB 250404A / EP250404a: NOT optical observations
  43. GRB 250331D: Swift-XRT afterglow detection
  44. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  45. EP250404a: REM optical/NIR observations
  46. EP250404a: Seimei/TriCCS optical counterpart detection
  47. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  48. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  49. EP250404a: LCO optical counterpart detection
  50. EP250404a: Xinglong decaying optical counterpart
  51. GRB 250403A: Montarrenti Observatory optical detection
  52. GRB 250403A: KAIT optical observations
  53. EP250404a: AKO Optical Afterglow Detection
  54. EP250404a: LAST detection of optical counterpart
  55. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  56. GRB 250327B: VIRT Optical Upper Limit
  57. EP250404a: Mephisto multi-band optical detection
  58. EP250321A: J band upper limit by SYSU 80cm telescope
  59. EP250404a: Nanshan/HMT optical counterpart detection
  60. EP250404a: Einstein Probe detection of an X-ray transient
  61. GRB 250403A: Swift/UVOT Detection
  62. GRB 250402A: Swift/UVOT Upper Limits
  63. EP250402a: Optical upper limit with Kinder observations
  64. GRB 250403A: REM NIR afterglow detection
  65. GRB 250403A: LCO optical counterpart detection
  66. GRB 250403A: JinShan optical observations
  67. GRB 250402A: EP-FXT afterglow detection
  68. GRB 250403A: Optical counterpart detection by LCO.
  69. EP250402a: EP-FXT follow-up observations
  70. GRB 250403A: GMG Optical Observation
  71. GRB 250403A: 1.6m Mephisto multi-band optical detection
  72. GRB 250403A: SVOM/C-GFT optical observations
  73. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  74. GRB 250402A: REM optical/NIR upper limits
  75. GRB 250402A: LCO optical counterpart detection
  76. The EP-WXT trigger 01709133862 is a flaring star
  77. EP250402a: Einstein Probe detection of a fast X-ray transient
  78. GRB 250402A: SVOM/VT optical counterpart
  79. GRB 250402A: SVOM detection of a burst
  80. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  81. GRB 250329B: Swift/UVOT Upper Limit
  82. GRB 250329A: Swift/UVOT Upper Limit
  83. GRB 250327B: Swift/UVOT Detection
  84. GRB 250327A: Swift/UVOT Upper Limits
  85. GRB 250331E: SVOM/GRM observation
  86. GRB 250327B: Kilonova-Catcher Observations
  87. GRB 250331D: Fermi GBM observation
  88. GRB 250331C: Swift/UVOT Upper Limits
  89. GRB 250331B: Swift/UVOT Upper Limits
  90. GRB 250328A: AbAO AS-32 Optical Observations
  91. GRB 250219A: NOT candidate host galaxy detection
  92. GRB 250330B: SVOM/GRM observation of a short burst
  93. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  94. GRB 250331C: Enhanced Swift-XRT position
  95. GRB 250331B: Enhanced Swift-XRT position
  96. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  97. GRB 250330A: VLT/FORS2 Afterglow Detection
  98. GRB20250327B: 45th Parallel Observatory upper limit
  99. GRB 250328A: Swift/UVOT Detection
  100. GRB 250328A: Swift-XRT refined Analysis

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