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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.

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

32502 results found.

  1. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  2. IPN triangulation of GRB 250407A
  3. EP250407a: Global MASTER-Net observations report
  4. GRB 250407A: LCO detection of a fading optical counterpart
  5. Fermi-LAT gamma-ray observations of IceCube-250406A
  6. EP250407a: Swift-XRT observations
  7. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  8. Konus-Wind detection of GRB 250407A
  9. GRB 250407A: SVOM/GRM observation of a bright long burst
  10. GRB 250407A: EP-WXT afterglow detection
  11. EP250407a: EP-WXT detection of a fast X-ray transient
  12. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  13. GRB 250407A: KAIT Optical Afterglow Candidate
  14. IceCube-250406A: No candidates from the Zwicky Transient Facility
  15. GRB 250407A: Fermi GBM Detection
  16. GRB 250407A: Swift-XRT afterglow detection
  17. Fermi GRB 250407A: Global MASTER-Net observations report
  18. GRB 250407A: Swift ToO observations
  19. GRB 250407A: SRG/ART-XC afterglow detection
  20. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  21. Konus-Wind detection of GRB 250406B (short/hard)
  22. IPN triangulation of GRB 250406B (short/hard)
  23. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  24. GRB 250406A: AstroSat CZTI detection
  25. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  26. Fermi GRB 250406A: Global MASTER-Net observations report
  27. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  28. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  29. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  30. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  31. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  32. Konus-Wind detection of GRB 250404A / EP250404a
  33. GRB 250404A / EP250404a: Mondy optical observations
  34. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  35. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  36. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  37. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  38. EP250402a: Optical upper limit with PD 1.3m observations
  39. GRB 250404A / EP250404a: NOT optical observations
  40. GRB 250403A: AstroSat CZTI detection
  41. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  42. EP250404a: REM optical/NIR observations
  43. EP250404a: Seimei/TriCCS optical counterpart detection
  44. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  45. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  46. EP250404a: LCO optical counterpart detection
  47. Fermi GRB 250404A: Global MASTER-Net observations report
  48. GRB 250403A: Montarrenti Observatory optical detection
  49. EP250404a: Global MASTER-Net observations report
  50. GRB 250403A: KAIT optical observations
  51. EP250404a: AKO Optical Afterglow Detection
  52. EP250404a: LAST detection of optical counterpart
  53. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  54. EP250404a: Xinglong-2.16m spectroscopic redshift
  55. GRB 250403A: Fermi GBM observations
  56. GRB 250327B: VIRT Optical Upper Limit
  57. EP250404a: Mephisto multi-band optical detection
  58. GRB 250331C Swift-BAT refined analysis
  59. GRB 250331B Swift-BAT refined analysis
  60. GRB 250330A Swift-BAT refined analysis
  61. EP250321A: J band upper limit by SYSU 80cm telescope
  62. EP250404a: BOOTES-4/JGT optical afterglow detection
  63. EP250404a: Nanshan/HMT optical counterpart detection
  64. EP250404a: Einstein Probe detection of an X-ray transient
  65. GRB 250402A: Mondy optical observations
  66. GRB 250403A: Swift/UVOT Detection
  67. GRB 250402A: Swift/UVOT Upper Limits
  68. EP250402a: Optical upper limit with Kinder observations
  69. GRB 250403A: SVOM/VT optical observation
  70. GRB 250403A: REM NIR afterglow detection
  71. GRB 250403A: LCO optical counterpart detection
  72. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  73. GRB 250403A: JinShan optical observations
  74. GRB 250402A: EP-FXT afterglow detection
  75. GRB 250403A: Optical counterpart detection by LCO.
  76. EP250402a: EP-FXT follow-up observations
  77. GRB 250403A: Swift-XRT observations
  78. GRB 250322A: 10 GHz VLA radio upper limits
  79. Fermi GRB 250403A: Global MASTER-Net observations report
  80. GRB 250403A: GOTO optical counterpart follow-up observations
  81. GRB 250402A: NUTTelA-TAO Early Optical Limits
  82. GRB 250403A: GMG Optical Observation
  83. GRB 250403A: 1.6m Mephisto multi-band optical detection
  84. GRB 250402A: Fermi GBM Observation
  85. GRB 250403A: SVOM/C-GFT optical observations
  86. GRB 250403A: GOTO detection of the optical afterglow
  87. GRB 250402A: Swift-XRT observations
  88. GRB 250403A : SVOM detection of a burst
  89. GRB 250225B: VLT host galaxy redshift z = 0.950
  90. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  91. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  92. GRB 250402A: REM optical/NIR upper limits
  93. GRB 250402A: LCO optical counterpart detection
  94. GRB 250402A: refined SVOM/MXT data analysis
  95. GRB 250402A: SVOM/VT optical counterpart
  96. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  97. GRB 250314A: ALMA detection
  98. GRB 250329B: Swift/UVOT Upper Limit
  99. GRB 250329A: Swift/UVOT Upper Limit
  100. GRB 250327B: Swift/UVOT Detection

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