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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"

24887 results found.

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

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