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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"

4994 results found.

  1. Fermi GRB 250601A: Global MASTER-Net observations report
  2. EP#01709177494: SVOM/VT optical observations
  3. GRB 250530C: BOOTES-7 optical upper limit
  4. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  5. Fermi trigger No 770047117: Global MASTER-Net observations report
  6. Fermi trigger No 769611916: Global MASTER-Net observations report
  7. Fermi GRB 250522B: Global MASTER-Net observations report
  8. Fermi GRB 250521D: Global MASTER-Net observations report
  9. GRB 250521D: DDOTI Optical Upper Limit
  10. GRB 250520A: 10 GHz VLA radio source
  11. GRB 250516A: COLIBRÍ optical upper limit
  12. Fermi GRB 250516A: Global MASTER-Net observations report
  13. Fermi GRB 250512A: Global MASTER-Net observations report
  14. GRB 250507B: AstroSat CZTI detection
  15. EP250512a: Global MASTER-Net observations report
  16. GRB 250507B: GRBAlpha detection
  17. EP250511a: COLIBRÍ optical counterpart candidate
  18. EP250511a: BOOTES-5 optical upper limit
  19. Fermi GRB 250510C: Global MASTER-Net observations report
  20. GRB 250509A: Fermi GBM Observation
  21. Fermi GRB 250509A: Global MASTER-Net observations report
  22. Swift GRB 250509A: Global MASTER-Net observations report
  23. GRB 250509A: Swift detection of a burst
  24. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  25. IceCube Alert 250506.59: Global MASTER-Net observations report
  26. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  27. GRB 250504A: REM optical/NIR observations
  28. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  29. Fermi trigger No 767623859: Global MASTER-Net observations report
  30. EP250427A: COLIBRÍ Continuing Optical Observations
  31. EP250427A: COLIBRÍ Optical Detection
  32. EP 250427a: BOOTES-7 optical afterglow candidate
  33. EP250427a: Global MASTER-Net observations report
  34. GRB 250424A: SVOM/VT optical observation
  35. Fermi-LAT gamma-ray observations of IceCube-250421A
  36. GRB 250424A: BlackGEM optical afterglow detection
  37. IceCube Alert 250421.71: Global MASTER-Net observations report
  38. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  39. EP250225a: SVOM/VT optical brightening
  40. IceCube 250414.324: DDOTI Optical Observations
  41. Fermi trigger No 766148493: Global MASTER-Net observations report
  42. Fermi trigger No 766173972: Global MASTER-Net observations report
  43. GRB 250411A: Fermi GBM Final Real-time Localization
  44. GRB 250407A: Continued KAIT/Nickel optical observations
  45. GRB 250407A: Mondy and AbAO Optical Observations
  46. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  47. IPN triangulation of GRB 250407A
  48. Fermi GRB 250407A: Global MASTER-Net observations report
  49. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  50. Fermi trigger No 765619921: Global MASTER-Net observations report
  51. GRB 250404A / EP250404a: Mondy optical observations
  52. GRB 250404A / EP250404a: NOT optical observations
  53. Fermi GRB 250404A: Global MASTER-Net observations report
  54. EP250404a: Global MASTER-Net observations report
  55. GRB 250402B: AstroSat CZTI detection of a short burst
  56. Fermi GRB 250331E: Global MASTER-Net observations report
  57. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  58. GRB 250331C: Swift detection of a burst
  59. GRB 250331A: MAXI/GSC detection
  60. Fermi GRB 250330A: Global MASTER-Net observations report
  61. IceCube Alert 250330.35: Global MASTER-Net observations report
  62. GRB 250329A: SVOM/VT optical counterpart confirmation
  63. GRB 250327B: LCO optical counterpart detection
  64. EP250321a: LCO optical counterpart detection
  65. EP250321a: Einstein Probe detection of an X-ray transient
  66. EP250226a/GRB 250226A: KAIT optical observations
  67. Fermi trigger No 763933627: Global MASTER-Net observations report
  68. Fermi GRB 250316A: Global MASTER-Net observations report
  69. GRB 250314A: Swift XRT Detection
  70. EP250315a: optical counterpart candidate detected by Gemini North
  71. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  72. Fermi GRB 250313A: Global MASTER-Net observations report
  73. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  74. GRB 250312A: Swift detection of a burst
  75. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  76. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  77. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  78. GRB 250309B / IceCube-250309A: GECAM-B observations
  79. GRB 250309B / AT2025dws: SAO RAS optical observations
  80. GRB 250309B / AT2025dws: Swift-UVOT detection
  81. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  82. GRB 250309B: Fermi GBM Observation
  83. Fermi GRB 250309B: Global MASTER-Net observations report
  84. Fermi GRB 250309A: Global MASTER-Net observations report
  85. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  86. IceCube-250309A: No candidates from the Zwicky Transient Facility
  87. Fermi-LAT gamma-ray observations of IceCube-250309A
  88. GRB 250309B: Fermi GBM Final Localization
  89. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  90. IceCube Alert 250309.32: Global MASTER-Net observations report
  91. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  92. EP250308a: Global MASTER-Net observations report
  93. Fermi GRB 250307A: Global MASTER-Net observations report
  94. Fermi trigger No 762963055: Global MASTER-Net observations report
  95. The EP-WXT trigger 01709132323 is likely a flaring star
  96. Fermi GRB 250305A: Global MASTER-Net observations report
  97. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  98. EP250302a: SAO RAS optical observations
  99. EP250302a: Nanshan/HMT optical counterpart detection
  100. GRB 250225B: VLT/HAWKI near-infrared observations

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