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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"

39158 results found.

  1. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  2. EP250427a: TRT optical counterpart detection
  3. EP250427a: Global MASTER-Net observations report
  4. IceCube Alert 250426.74: Global MASTER-Net observations report
  5. GRB 250424A: Swift-BAT refined analysis
  6. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  7. GRB 250424A: SVOM/GRM observation of a long burst
  8. GRB 250424A: PRIME near-infrared detection
  9. GRB 250424A: WINTER J-band detection
  10. GRB 250424A: EIRSAT-1 GMOD Detection
  11. GRB 250424A: SVOM/VT optical observation
  12. GRB 250419A: Mondy Optical Observations
  13. GRB 250424A: Swift/UVOT Detection
  14. Konus-Wind detection of GRB 250424A
  15. Fermi-LAT gamma-ray observations of IceCube-250421A
  16. GRB 250424A: Skynet Optical Observations
  17. GRB 250424A: Kilonova-Catcher optical afterglow detection
  18. GRB 250419a: Continued Liverpool Telescope observations
  19. GRB 250419A: Liverpool Telescope optical upper limit
  20. GRB 250407A: GRBAlpha detection
  21. GRB 250404A / EP250404a: GRBAlpha detection
  22. GRB 250330B: GRBAlpha detection
  23. GRB 250419A: SVOM/ECLAIRs refined analysis
  24. GRB 250424A: Swift-XRT refined Analysis
  25. GRB 250424A: Enhanced Swift-XRT position
  26. GRB 250424A: AstroSat CZTI detection of a bright long burst
  27. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  28. GRB 250424A: BlackGEM optical afterglow detection
  29. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  30. GRB 250424A: likely host galaxy
  31. GRB 250424A: DDOTI Afterglow Detection
  32. GRB 250424A: REM optical/NIR afterglow detection
  33. GRB 250424A: Swift detection of a burst with an optical counterpart
  34. Swift GRB 250424A: Global MASTER-Net observations report
  35. Swift GRB 250424A: Global MASTER-Net OT detection
  36. EP250421a: Nickel optical upper limit
  37. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  38. EP250421a: Upper limits from Fermi-GBM Observations
  39. SVOM/sb25042207: GOTO optical upper limits
  40. GRB 250421A: AstroSat CZTI detection
  41. GRB250419A: VLA radio detection
  42. GRB 250419A: Mephisto Multi-band Optical Detection
  43. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  44. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  45. GRB 250419A: Optical Observations via Virtual Telescope Project
  46. EP250421a: REM optical upper limit
  47. GRB 250419A: Mondy Continued Optical Observations
  48. Fermi GRB 250421A: Global MASTER-Net observations report
  49. EP250421a: Global MASTER-Net observations report
  50. GRB 250421B: AstroSat CZTI detection of a bright long burst
  51. EP250421a: Mephisto optical counterpart confirmation
  52. IceCube Alert 250421.71: Global MASTER-Net observations report
  53. EP250421a: JinShan likely optical counterpart
  54. GRB 250421A: Fermi GBM Final Real-time Localization
  55. GRB 250419A: Liverpool Telescope observations
  56. GRB 250419A: LCO optical observation
  57. GRB 250419A: JinShan optical observations
  58. GRB 250419A: SVOM/VT optical continuous observations
  59. GRB 250419A: SVOM/C-GFT optical observations
  60. GRB 250419A: Swift/UVOT Follow up
  61. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  62. GRB 250419A: LCO optical afterglow multi-band observations
  63. GRB 250419A: Mondy and AbAO Optical Observations
  64. GRB 250419A: Liverpool Telescope observations
  65. GRB 250419A: AKO Optical Afterglow Detection
  66. GRB 250419A: MASTER optical afterglow observation
  67. GRB 250407A: rest-frame energetics from Konus-Wind observation
  68. GRB 250419A: Swift-XRT localisation
  69. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  70. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  71. GRB 250419A: Swift-XRT refined Analysis
  72. GRB 250419A: GOTO optical counterpart detection
  73. GRB 250419A: KAIT optical afterglow observations
  74. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  75. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  76. GRB 250419A: SVOM detection of a soft burst
  77. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  78. Konus-Wind detection of GRB 250403A
  79. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  80. EP250416a: Gemini South-GMOS optical counterpart
  81. SVOM/sb25041603 is not a GRB
  82. EP250416a: GSP optical upper limit
  83. EP250416a: Global MASTER-Net observations report
  84. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  85. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  86. IceCube-250416A: Global MASTER-Net observations report
  87. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  88. GRB 250416B: Fermi GBM Final Real-time Localization
  89. GRB 250416A: Fermi GBM Final Real-time Localization
  90. SVOM/sb25041603: SVOM detection of an X-ray transient
  91. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  92. GRB 250413A: AstroSat CZTI detection
  93. EP250304a: ATCA radio observations
  94. GRB 250412A: AstroSat CZTI detection
  95. Fermi trigger No 766148493: Global MASTER-Net observations report
  96. Fermi trigger No 766173972: Global MASTER-Net observations report
  97. GRB 250411A: DDOTI Optical Observations
  98. Fermi GRB 250411A: Global MASTER-Net observations report
  99. GRB 250411A: Fermi GBM Final Real-time Localization
  100. GRB 250407A: Continued KAIT/Nickel optical observations

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