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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"

24797 results found.

  1. GRB 250502A: Mondy and Tien-Shan Optical Observations
  2. GRB 250502A: KAIT optical observations
  3. GRB 250502A: Montarrenti Observatory optical detection
  4. GRB 250502A: Swift-XRT afterglow detection
  5. GRB 250502A: NOT optical observations
  6. GRB 250502B: AstroSat CZTI detection
  7. GRB 250502A: AKO Optical Afterglow Detection
  8. GRB 250502A: LCO optical counterpart detection
  9. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  10. GRB 250407A: VZLUSAT-2 detection
  11. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  12. GRB 250502B: DDOTI Optical Observations
  13. GRB 250430A: Swift-XRT refined Analysis
  14. GRB 250502A: Early optical counterpart detection by LCO.
  15. GRB 250430A: Swift/UVOT Detection
  16. GRB 250502A: TRT optical afterglow confirmation
  17. GRB 250430A: Enhanced Swift-XRT position
  18. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  19. GRB 250502A: SVOM detection of a burst
  20. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  21. GRB 250430A: KAIT optical observations
  22. GRB 250430A / EP250430a: J-band upper limits with WINTER
  23. GRB 250430A: NUTTelA-TAO Early Measurements
  24. GRB 250430A: DDOTI Optical Observations
  25. GRB 250430A: Leavitt Observatory optical upper limit
  26. GRB 250430A: Bassano Bresciano Observatory upper limit
  27. GRB 250430A : MITSuME Akeno optical upper limits
  28. SVOM/sb25043004: EP-FXT observations
  29. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  30. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  31. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  32. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  33. GRB 250430A: AKO Optical Afterglow Detection
  34. GRB 250430A: Kanata optical upper limit
  35. EP 250427A: Optical counterpart detection by LCO.
  36. GRB 250430A: Swift detection of a burst with optical counterpart
  37. EP250427a/GRB250427A: HCT optical follow-up
  38. SVOM/sb25043004: SVOM detection of a X-ray transient
  39. EP250428b: GROWTH-India telescope optical upper limit
  40. EP250428b: SAO RAS optical upper limit
  41. EP250428b: LAST optical upper limit
  42. GRB 250427A: Swift/UVOT Detection
  43. EP250428b: Global MASTER-Net observations report
  44. EP250428b: Einstein Probe detection of a fast X-ray transient
  45. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  46. EP250427a: Lesedi optical counterpart detection
  47. EP250427A: COLIBRÍ Continuing Optical Observations
  48. GRB250427A/EP250427a GIT optical afterglow detection:
  49. EP250427a: LT optical counterpart detection
  50. GRB 250427A: Swift-XRT refined Analysis
  51. EP250427a / GRB 250427A: LCO optical counterpart detection
  52. EP250427a: REM optical/NIR afterglow detection
  53. GRB 250424A: LCO optical observation
  54. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  55. EP250427A: COLIBRÍ Optical Detection
  56. EP250427a: TRT optical counterpart detection
  57. EP250427a: Einstein Probe detection of a fast X-ray transient
  58. GRB 250424A: Swift-BAT refined analysis
  59. GRB 250424A: SVOM/GRM observation of a long burst
  60. GRB 250424A: PRIME near-infrared detection
  61. GRB 250424A: WINTER J-band detection
  62. GRB 250424A: EIRSAT-1 GMOD Detection
  63. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  64. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  65. GRB 250419A: Mondy Optical Observations
  66. GRB 250424A: Swift/UVOT Detection
  67. Fermi-LAT gamma-ray observations of IceCube-250421A
  68. GRB 250424A: Skynet Optical Observations
  69. GRB 250424A: Kilonova-Catcher optical afterglow detection
  70. GRB 250330B: GRBAlpha detection
  71. GRB 250424A: Swift-XRT refined Analysis
  72. GRB 250424A: Enhanced Swift-XRT position
  73. GRB 250424A: AstroSat CZTI detection of a bright long burst
  74. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  75. GRB 250424A: BlackGEM optical afterglow detection
  76. GRB 250424A: DDOTI Afterglow Detection
  77. GRB 250424A: REM optical/NIR afterglow detection
  78. GRB 250424A: Swift detection of a burst with an optical counterpart
  79. Swift GRB 250424A: Global MASTER-Net OT detection
  80. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  81. EP250421a: Nickel optical upper limit
  82. EP250421a: Upper limits from Fermi-GBM Observations
  83. SVOM/sb25042207: SVOM detection of an X-ray transient
  84. IceCube-250421A: DDOTI Detection of the LAST Candidate
  85. GRB 250419A: Mephisto Multi-band Optical Detection
  86. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  87. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  88. EP250421a: NOT optical observations
  89. GRB 250419A: Optical Observations via Virtual Telescope Project
  90. EP250421a: REM optical upper limit
  91. EP250421A: COLIBRÍ Optical Upper Limit
  92. GRB 250419A: Mondy Continued Optical Observations
  93. GRB 250421B: AstroSat CZTI detection of a bright long burst
  94. EP250421a: Einstein Probe detection of an X-ray transient
  95. EP250421a: Mephisto optical counterpart confirmation
  96. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  97. EP250421a: JinShan likely optical counterpart
  98. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  99. GRB 250419A: LCO optical observation
  100. GRB 250419A: JinShan optical observations

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