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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"

24592 results found.

  1. GRB 250502A: NOT optical observations
  2. GRB 250502B: AstroSat CZTI detection
  3. GRB 250502A: AKO Optical Afterglow Detection
  4. GRB 250502A: LCO optical counterpart detection
  5. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  6. GRB 250407A: VZLUSAT-2 detection
  7. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  8. GRB 250502B: DDOTI Optical Observations
  9. GRB 250430A: Swift-XRT refined Analysis
  10. GRB 250502A: Early optical counterpart detection by LCO.
  11. GRB 250430A: Swift/UVOT Detection
  12. GRB 250502A: TRT optical afterglow confirmation
  13. GRB 250430A: Enhanced Swift-XRT position
  14. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  15. GRB 250502A: SVOM detection of a burst
  16. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  17. GRB 250430A: KAIT optical observations
  18. GRB 250430A / EP250430a: J-band upper limits with WINTER
  19. GRB 250430A: NUTTelA-TAO Early Measurements
  20. GRB 250430A: DDOTI Optical Observations
  21. GRB 250430A: Leavitt Observatory optical upper limit
  22. GRB 250430A: Bassano Bresciano Observatory upper limit
  23. GRB 250430A : MITSuME Akeno optical upper limits
  24. SVOM/sb25043004: EP-FXT observations
  25. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  26. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  27. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  28. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  29. GRB 250430A: AKO Optical Afterglow Detection
  30. GRB 250430A: Kanata optical upper limit
  31. EP 250427A: Optical counterpart detection by LCO.
  32. GRB 250430A: Swift detection of a burst with optical counterpart
  33. EP250427a/GRB250427A: HCT optical follow-up
  34. SVOM/sb25043004: SVOM detection of a X-ray transient
  35. EP250428b: GROWTH-India telescope optical upper limit
  36. EP250428b: SAO RAS optical upper limit
  37. EP250428b: LAST optical upper limit
  38. GRB 250427A: Swift/UVOT Detection
  39. EP250428b: Global MASTER-Net observations report
  40. EP250428b: Einstein Probe detection of a fast X-ray transient
  41. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  42. EP250427a: Lesedi optical counterpart detection
  43. EP250427A: COLIBRÍ Continuing Optical Observations
  44. GRB250427A/EP250427a GIT optical afterglow detection:
  45. EP250427a: LT optical counterpart detection
  46. GRB 250427A: Swift-XRT refined Analysis
  47. EP250427a / GRB 250427A: LCO optical counterpart detection
  48. EP250427a: REM optical/NIR afterglow detection
  49. GRB 250424A: LCO optical observation
  50. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  51. EP250427A: COLIBRÍ Optical Detection
  52. EP250427a: TRT optical counterpart detection
  53. EP250427a: Einstein Probe detection of a fast X-ray transient
  54. GRB 250424A: Swift-BAT refined analysis
  55. GRB 250424A: SVOM/GRM observation of a long burst
  56. GRB 250424A: PRIME near-infrared detection
  57. GRB 250424A: WINTER J-band detection
  58. GRB 250424A: EIRSAT-1 GMOD Detection
  59. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  60. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  61. GRB 250419A: Mondy Optical Observations
  62. GRB 250424A: Swift/UVOT Detection
  63. Fermi-LAT gamma-ray observations of IceCube-250421A
  64. GRB 250424A: Skynet Optical Observations
  65. GRB 250424A: Kilonova-Catcher optical afterglow detection
  66. GRB 250330B: GRBAlpha detection
  67. GRB 250424A: Swift-XRT refined Analysis
  68. GRB 250424A: Enhanced Swift-XRT position
  69. GRB 250424A: AstroSat CZTI detection of a bright long burst
  70. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  71. GRB 250424A: BlackGEM optical afterglow detection
  72. GRB 250424A: DDOTI Afterglow Detection
  73. GRB 250424A: REM optical/NIR afterglow detection
  74. GRB 250424A: Swift detection of a burst with an optical counterpart
  75. Swift GRB250424A: Global MASTER-Net OT detection
  76. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  77. EP250421a: Nickel optical upper limit
  78. EP250421a: Upper limits from Fermi-GBM Observations
  79. SVOM/sb25042207: SVOM detection of an X-ray transient
  80. IceCube-250421A: DDOTI Detection of the LAST Candidate
  81. GRB 250419A: Mephisto Multi-band Optical Detection
  82. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  83. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  84. EP250421a: NOT optical observations
  85. GRB 250419A: Optical Observations via Virtual Telescope Project
  86. EP250421a: REM optical upper limit
  87. EP250421A: COLIBRÍ Optical Upper Limit
  88. GRB 250419A: Mondy Continued Optical Observations
  89. GRB 250421B: AstroSat CZTI detection of a bright long burst
  90. EP250421a: Einstein Probe detection of an X-ray transient
  91. EP250421a: Mephisto optical counterpart confirmation
  92. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  93. EP250421a: JinShan likely optical counterpart
  94. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  95. GRB 250419A: LCO optical observation
  96. GRB 250419A: JinShan optical observations
  97. GRB 250419A: SVOM/C-GFT optical observations
  98. GRB 250419A: Swift/UVOT Follow up
  99. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  100. GRB 250419A: LCO optical afterglow multi-band observations

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