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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"

38302 results found.

  1. Fermi GRB 250502B: Global MASTER-Net observations report
  2. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  3. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  4. GRB 250502B: Fermi GBM Final Real-time Localization
  5. GRB 250502A: SVOM detection of a burst
  6. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  7. GRB 250430A: SVOM/VT optical observations
  8. GRB 250430A: KAIT optical observations
  9. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  10. GRB 250430A / EP250430a: J-band upper limits with WINTER
  11. GRB 250430A: NUTTelA-TAO Early Measurements
  12. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  13. GRB 250430A: DDOTI Optical Observations
  14. GRB 250430A: Leavitt Observatory optical upper limit
  15. GRB 250430A: Bassano Bresciano Observatory upper limit
  16. GRB 250430A : MITSuME Akeno optical upper limits
  17. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  18. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  19. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  20. GRB 250430A: AKO Optical Afterglow Detection
  21. GRB 250430A: Kanata optical upper limit
  22. EP 250427A: Optical counterpart detection by LCO.
  23. GRB 250430A: Swift detection of a burst with optical counterpart
  24. Swift GRB250430.73: Global MASTER-Net observations report
  25. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  26. SVOM/sb25043004: SVOM detection of a X-ray transient
  27. Fermi trigger No 767623859: Global MASTER-Net observations report
  28. EP250428b: GROWTH-India telescope optical upper limit
  29. EP250428b: SAO RAS optical upper limit
  30. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  31. GRB 250427A: Swift/UVOT Detection
  32. EP250428b: Global MASTER-Net observations report
  33. EP250427a / GRB 250427A: OHP/T193 photometric observations
  34. EP250427a: EP-FXT follow-up observations
  35. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  36. EP250427a: Lesedi optical counterpart detection
  37. GRB250427A/EP250427a GIT optical afterglow detection:
  38. EP250427a: LT optical counterpart detection
  39. GRB 250427A: Swift-XRT refined Analysis
  40. EP250427a / GRB 250427A: LCO optical counterpart detection
  41. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  42. EP250427A/GRB250427A: Keck/LRIS redshift
  43. EP250427a: REM optical/NIR afterglow detection
  44. GRB 250424A: LCO optical observation
  45. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  46. EP250427a: TRT optical counterpart detection
  47. EP250427a: Global MASTER-Net observations report
  48. IceCube Alert 250426.74: Global MASTER-Net observations report
  49. GRB 250424A: Swift-BAT refined analysis
  50. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  51. GRB 250424A: SVOM/GRM observation of a long burst
  52. GRB 250424A: PRIME near-infrared detection
  53. GRB 250424A: WINTER J-band detection
  54. GRB 250424A: EIRSAT-1 GMOD Detection
  55. GRB 250424A: SVOM/VT optical observation
  56. GRB 250419A: Mondy Optical Observations
  57. GRB 250424A: Swift/UVOT Detection
  58. Konus-Wind detection of GRB 250424A
  59. Fermi-LAT gamma-ray observations of IceCube-250421A
  60. GRB 250424A: Skynet Optical Observations
  61. GRB 250424A: Kilonova-Catcher optical afterglow detection
  62. GRB 250419a: Continued Liverpool Telescope observations
  63. GRB 250419A: Liverpool Telescope optical upper limit
  64. GRB 250407A: GRBAlpha detection
  65. GRB 250404A / EP250404a: GRBAlpha detection
  66. GRB 250330B: GRBAlpha detection
  67. GRB 250419A: SVOM/ECLAIRs refined analysis
  68. GRB 250424A: Swift-XRT refined Analysis
  69. GRB 250424A: Enhanced Swift-XRT position
  70. GRB 250424A: AstroSat CZTI detection of a bright long burst
  71. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  72. GRB 250424A: BlackGEM optical afterglow detection
  73. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  74. GRB 250424A: likely host galaxy
  75. GRB 250424A: DDOTI Afterglow Detection
  76. GRB 250424A: REM optical/NIR afterglow detection
  77. GRB 250424A: Swift detection of a burst with an optical counterpart
  78. Swift GRB 250424A: Global MASTER-Net observations report
  79. Swift GRB 250424A: Global MASTER-Net OT detection
  80. EP250421a: Nickel optical upper limit
  81. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  82. EP250421a: Upper limits from Fermi-GBM Observations
  83. SVOM/sb25042207: GOTO optical upper limits
  84. GRB 250421A: AstroSat CZTI detection
  85. GRB250419A: VLA radio detection
  86. GRB 250419A: Mephisto Multi-band Optical Detection
  87. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  88. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  89. GRB 250419A: Optical Observations via Virtual Telescope Project
  90. EP250421a: REM optical upper limit
  91. GRB 250419A: Mondy Continued Optical Observations
  92. Fermi GRB 250421A: Global MASTER-Net observations report
  93. EP250421a: Global MASTER-Net observations report
  94. GRB 250421B: AstroSat CZTI detection of a bright long burst
  95. EP250421a: Mephisto optical counterpart confirmation
  96. IceCube Alert 250421.71: Global MASTER-Net observations report
  97. EP250421a: JinShan likely optical counterpart
  98. GRB 250421A: Fermi GBM Final Real-time Localization
  99. GRB 250419A: Liverpool Telescope observations
  100. GRB 250419A: LCO optical observation

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