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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"

37513 results found.

  1. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  2. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  3. GRB 250502B: Fermi GBM Final Real-time Localization
  4. GRB 250502A: SVOM detection of a burst
  5. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  6. GRB 250430A: SVOM/VT optical observations
  7. GRB 250430A: KAIT optical observations
  8. GRB 250430A / EP250430a: J-band upper limits with WINTER
  9. GRB 250430A: NUTTelA-TAO Early Measurements
  10. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  11. GRB 250430A: DDOTI Optical Observations
  12. GRB 250430A: Leavitt Observatory optical upper limit
  13. GRB 250430A: Bassano Bresciano Observatory upper limit
  14. GRB 250430A : MITSuME Akeno optical upper limits
  15. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  16. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  17. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  18. GRB 250430A: AKO Optical Afterglow Detection
  19. GRB 250430A: Kanata optical upper limit
  20. EP 250427A: Optical counterpart detection by LCO.
  21. GRB 250430A: Swift detection of a burst with optical counterpart
  22. EP250427a/GRB250427A: HCT optical follow-up
  23. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  24. Fermi trigger No 767623859: Global MASTER-Net observations report
  25. EP250428b: SAO RAS optical upper limit
  26. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  27. GRB 250427A: Swift/UVOT Detection
  28. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  29. EP250427a / GRB 250427A: OHP/T193 photometric observations
  30. EP250427a: EP-FXT follow-up observations
  31. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  32. GRB250427A/EP250427a GIT optical afterglow detection:
  33. GRB 250427A: Swift-XRT refined Analysis
  34. EP250427a / GRB 250427A: LCO optical counterpart detection
  35. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  36. EP250427A/GRB250427A: Keck/LRIS redshift
  37. EP250427a: REM optical/NIR afterglow detection
  38. GRB 250424A: LCO optical observation
  39. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  40. GRB 250424A: Swift-BAT refined analysis
  41. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  42. GRB 250424A: SVOM/GRM observation of a long burst
  43. GRB 250424A: PRIME near-infrared detection
  44. GRB 250424A: WINTER J-band detection
  45. GRB 250424A: EIRSAT-1 GMOD Detection
  46. GRB 250424A: SVOM/VT optical observation
  47. GRB 250419A: Mondy Optical Observations
  48. GRB 250424A: Swift/UVOT Detection
  49. Konus-Wind detection of GRB 250424A
  50. Fermi-LAT gamma-ray observations of IceCube-250421A
  51. GRB 250424A: Skynet Optical Observations
  52. GRB 250424A: Kilonova-Catcher optical afterglow detection
  53. GRB 250419a: Continued Liverpool Telescope observations
  54. GRB 250419A: Liverpool Telescope optical upper limit
  55. GRB 250407A: GRBAlpha detection
  56. GRB 250404A / EP250404a: GRBAlpha detection
  57. GRB 250330B: GRBAlpha detection
  58. GRB 250419A: SVOM/ECLAIRs refined analysis
  59. GRB 250424A: Swift-XRT refined Analysis
  60. GRB 250424A: Enhanced Swift-XRT position
  61. GRB 250424A: AstroSat CZTI detection of a bright long burst
  62. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  63. GRB 250424A: BlackGEM optical afterglow detection
  64. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  65. GRB 250424A: likely host galaxy
  66. GRB 250424A: DDOTI Afterglow Detection
  67. GRB 250424A: REM optical/NIR afterglow detection
  68. GRB 250424A: Swift detection of a burst with an optical counterpart
  69. Swift GRB 250424A: Global MASTER-Net observations report
  70. Swift GRB 250424A: Global MASTER-Net OT detection
  71. EP250421a: Nickel optical upper limit
  72. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  73. EP250421a: Upper limits from Fermi-GBM Observations
  74. SVOM/sb25042207: GOTO optical upper limits
  75. GRB 250421A: AstroSat CZTI detection
  76. GRB250419A: VLA radio detection
  77. GRB 250419A: Mephisto Multi-band Optical Detection
  78. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  79. GRB 250419A: Optical Observations via Virtual Telescope Project
  80. GRB 250419A: Mondy Continued Optical Observations
  81. Fermi GRB 250421A: Global MASTER-Net observations report
  82. GRB 250421B: AstroSat CZTI detection of a bright long burst
  83. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  84. GRB 250421A: Fermi GBM Final Real-time Localization
  85. GRB 250419A: Liverpool Telescope observations
  86. GRB 250419A: LCO optical observation
  87. GRB 250419A: JinShan optical observations
  88. GRB 250419A: SVOM/VT optical continuous observations
  89. GRB 250419A: SVOM/C-GFT optical observations
  90. GRB 250419A: Swift/UVOT Follow up
  91. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  92. GRB 250419A: LCO optical afterglow multi-band observations
  93. GRB 250419A: Mondy and AbAO Optical Observations
  94. GRB 250419A: Liverpool Telescope observations
  95. GRB 250419A: AKO Optical Afterglow Detection
  96. GRB 250419A: MASTER optical afterglow observation
  97. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  98. GRB 250407A: rest-frame energetics from Konus-Wind observation
  99. GRB 250419A: Swift-XRT localisation
  100. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36

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