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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"

23410 results found.

  1. GRB 250424A: DDOTI Afterglow Detection
  2. GRB 250424A: REM optical/NIR afterglow detection
  3. GRB 250424A: Swift detection of a burst with an optical counterpart
  4. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  5. EP250421a: Nickel optical upper limit
  6. SVOM/sb25042207: XRT observations
  7. GRB 250421A: AstroSat CZTI detection
  8. IceCube-250421A: DDOTI Detection of the LAST Candidate
  9. GRB 250419A: Mephisto Multi-band Optical Detection
  10. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  11. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  12. EP250421a: NOT optical observations
  13. GRB 250419A: Optical Observations via Virtual Telescope Project
  14. EP250421a: REM optical upper limit
  15. EP250421a: Swift/XRT counterpart detection
  16. EP250421A: COLIBRÍ Optical Upper Limit
  17. GRB 250419A: Mondy Continued Optical Observations
  18. GRB 250421B: AstroSat CZTI detection of a bright long burst
  19. EP250421a: Einstein Probe detection of an X-ray transient
  20. EP250421a: Mephisto optical counterpart confirmation
  21. EP250421a: JinShan likely optical counterpart
  22. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  23. GRB 250419A: LCO optical observation
  24. GRB 250419A: JinShan optical observations
  25. GRB 250419A: SVOM/C-GFT optical observations
  26. GRB 250419A: Swift/UVOT Follow up
  27. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  28. GRB 250419A: LCO optical afterglow multi-band observations
  29. GRB 250419A: Mondy and AbAO Optical Observations
  30. GRB 250419A: AKO Optical Afterglow Detection
  31. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  32. GRB 250419A: GOTO optical counterpart detection
  33. GRB 250419A: KAIT optical afterglow observations
  34. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  35. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  36. GRB 250419A: SVOM detection of a soft burst
  37. EP250416a: Swift/XRT counterpart fading
  38. EP20250416a: Swift/XRT counterpart detection
  39. IceCube-250416A: DDOTI Optical Observations
  40. EP250416a: Gemini South-GMOS optical counterpart
  41. SVOM/sb25041603 is not a GRB
  42. EP250416a: Einstein Probe detection of an X-ray transient
  43. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  44. IceCube 250414.324: DDOTI Optical Observations
  45. GRB 250413A: AstroSat CZTI detection
  46. EP250304a: ATCA radio observations
  47. GRB 250412A: AstroSat CZTI detection
  48. EP250404a: Nanshan 0.43m Telescope optical observatios
  49. GRB 250411A: DDOTI Optical Observations
  50. GRB 250314A: e-MERLIN observations
  51. GRB 250407A: Mondy and AbAO Optical Observations
  52. EP250227a: Further NOT optical observations
  53. GRB 250320B: cubesat Avion detection
  54. IceCube-250406A: Swift-XRT observations
  55. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  56. IPN triangulation of GRB 250407A
  57. GRB 250407A: LCO detection of a fading optical counterpart
  58. EP250407a: Swift-XRT observations
  59. GRB 250407A: SVOM/GRM observation of a bright long burst
  60. GRB 250407A: EP-WXT afterglow detection
  61. EP250407a: EP-WXT detection of a fast X-ray transient
  62. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  63. GRB 250407A: KAIT Optical Afterglow Candidate
  64. IceCube-250406A: No candidates from the Zwicky Transient Facility
  65. GRB 250407A: Swift-XRT afterglow detection
  66. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  67. IPN triangulation of GRB 250406B (short/hard)
  68. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  69. IceCube 250406.951: DDOTI Optical Observations
  70. Fermi trigger No 765663719: Global MASTER-Net observations report
  71. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  72. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  73. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  74. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  75. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  76. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  77. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  78. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  79. EP250402a: Optical upper limit with PD 1.3m observations
  80. GRB 250404A / EP250404a: NOT optical observations
  81. GRB 250331D: Swift-XRT afterglow detection
  82. GRB 250403A: AstroSat CZTI detection
  83. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  84. EP250404a: REM optical/NIR observations
  85. EP250404a: Seimei/TriCCS optical counterpart detection
  86. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  87. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  88. EP250404a: LCO optical counterpart detection
  89. EP250404a: Xinglong decaying optical counterpart
  90. GRB 250403A: Montarrenti Observatory optical detection
  91. GRB 250403A: KAIT optical observations
  92. EP250404a: AKO Optical Afterglow Detection
  93. EP250404a: LAST detection of optical counterpart
  94. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  95. GRB 250327B: VIRT Optical Upper Limit
  96. EP250404a: Mephisto multi-band optical detection
  97. EP250321A: J band upper limit by SYSU 80cm telescope
  98. EP250404a: Nanshan/HMT optical counterpart detection
  99. EP250404a: Einstein Probe detection of an X-ray transient
  100. GRB 250403A: Swift/UVOT Detection

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