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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"

24598 results found.

  1. Fermi GRB 250504A: Global MASTER-Net observations report
  2. GRB 250504A: Swift detection of a burst
  3. GRB 250502A: Swift/UVOT Follow up
  4. GRB 250502A: Mondy and Tien-Shan Optical Observations
  5. GRB 250502A: KAIT optical observations
  6. GRB 250502A: Montarrenti Observatory optical detection
  7. GRB 250502A: Swift-XRT afterglow detection
  8. GRB 250502A: NOT optical observations
  9. GRB 250502B: AstroSat CZTI detection
  10. GRB 250502A: AKO Optical Afterglow Detection
  11. GRB 250502A: LCO optical counterpart detection
  12. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  13. GRB 250407A: VZLUSAT-2 detection
  14. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  15. GRB 250502B: DDOTI Optical Observations
  16. GRB 250430A: Swift-XRT refined Analysis
  17. GRB 250502A: Early optical counterpart detection by LCO.
  18. GRB 250430A: Swift/UVOT Detection
  19. GRB 250502A: TRT optical afterglow confirmation
  20. GRB 250430A: Enhanced Swift-XRT position
  21. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  22. GRB 250502A: SVOM detection of a burst
  23. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  24. GRB 250430A: KAIT optical observations
  25. GRB 250430A / EP250430a: J-band upper limits with WINTER
  26. GRB 250430A: NUTTelA-TAO Early Measurements
  27. GRB 250430A: DDOTI Optical Observations
  28. GRB 250430A: Leavitt Observatory optical upper limit
  29. GRB 250430A: Bassano Bresciano Observatory upper limit
  30. GRB 250430A : MITSuME Akeno optical upper limits
  31. SVOM/sb25043004: EP-FXT observations
  32. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  33. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  34. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  35. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  36. GRB 250430A: AKO Optical Afterglow Detection
  37. GRB 250430A: Kanata optical upper limit
  38. EP 250427A: Optical counterpart detection by LCO.
  39. GRB 250430A: Swift detection of a burst with optical counterpart
  40. EP250427a/GRB250427A: HCT optical follow-up
  41. SVOM/sb25043004: SVOM detection of a X-ray transient
  42. EP250428b: GROWTH-India telescope optical upper limit
  43. EP250428b: SAO RAS optical upper limit
  44. EP250428b: LAST optical upper limit
  45. GRB 250427A: Swift/UVOT Detection
  46. EP250428b: Global MASTER-Net observations report
  47. EP250428b: Einstein Probe detection of a fast X-ray transient
  48. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  49. EP250427a: Lesedi optical counterpart detection
  50. EP250427A: COLIBRÍ Continuing Optical Observations
  51. GRB250427A/EP250427a GIT optical afterglow detection:
  52. EP250427a: LT optical counterpart detection
  53. GRB 250427A: Swift-XRT refined Analysis
  54. EP250427a / GRB 250427A: LCO optical counterpart detection
  55. EP250427a: REM optical/NIR afterglow detection
  56. GRB 250424A: LCO optical observation
  57. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  58. EP250427A: COLIBRÍ Optical Detection
  59. EP250427a: TRT optical counterpart detection
  60. EP250427a: Einstein Probe detection of a fast X-ray transient
  61. GRB 250424A: Swift-BAT refined analysis
  62. GRB 250424A: SVOM/GRM observation of a long burst
  63. GRB 250424A: PRIME near-infrared detection
  64. GRB 250424A: WINTER J-band detection
  65. GRB 250424A: EIRSAT-1 GMOD Detection
  66. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  67. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  68. GRB 250419A: Mondy Optical Observations
  69. GRB 250424A: Swift/UVOT Detection
  70. Fermi-LAT gamma-ray observations of IceCube-250421A
  71. GRB 250424A: Skynet Optical Observations
  72. GRB 250424A: Kilonova-Catcher optical afterglow detection
  73. GRB 250330B: GRBAlpha detection
  74. GRB 250424A: Swift-XRT refined Analysis
  75. GRB 250424A: Enhanced Swift-XRT position
  76. GRB 250424A: AstroSat CZTI detection of a bright long burst
  77. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  78. GRB 250424A: BlackGEM optical afterglow detection
  79. GRB 250424A: DDOTI Afterglow Detection
  80. GRB 250424A: REM optical/NIR afterglow detection
  81. GRB 250424A: Swift detection of a burst with an optical counterpart
  82. Swift GRB250424A: Global MASTER-Net OT detection
  83. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  84. EP250421a: Nickel optical upper limit
  85. EP250421a: Upper limits from Fermi-GBM Observations
  86. SVOM/sb25042207: SVOM detection of an X-ray transient
  87. IceCube-250421A: DDOTI Detection of the LAST Candidate
  88. GRB 250419A: Mephisto Multi-band Optical Detection
  89. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  90. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  91. EP250421a: NOT optical observations
  92. GRB 250419A: Optical Observations via Virtual Telescope Project
  93. EP250421a: REM optical upper limit
  94. EP250421A: COLIBRÍ Optical Upper Limit
  95. GRB 250419A: Mondy Continued Optical Observations
  96. GRB 250421B: AstroSat CZTI detection of a bright long burst
  97. EP250421a: Einstein Probe detection of an X-ray transient
  98. EP250421a: Mephisto optical counterpart confirmation
  99. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  100. EP250421a: JinShan likely optical counterpart

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