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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"

4882 results found.

  1. Fermi GRB 250512A: Global MASTER-Net observations report
  2. GRB 250507B: AstroSat CZTI detection
  3. EP250512a: Global MASTER-Net observations report
  4. GRB 250507B: GRBAlpha detection
  5. EP250511a: COLIBRÍ optical counterpart candidate
  6. EP250511a: BOOTES-5 optical upper limit
  7. Fermi GRB 250510C: Global MASTER-Net observations report
  8. GRB 250509A: Fermi GBM Observation
  9. Fermi GRB 250509A: Global MASTER-Net observations report
  10. Swift GRB 250509A: Global MASTER-Net observations report
  11. GRB 250509A: Swift detection of a burst
  12. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  13. IceCube Alert 250506.59: Global MASTER-Net observations report
  14. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  15. GRB 250504A: REM optical/NIR observations
  16. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  17. Fermi trigger No 767623859: Global MASTER-Net observations report
  18. EP250427A: COLIBRÍ Continuing Optical Observations
  19. EP250427A: COLIBRÍ Optical Detection
  20. EP 250427a: BOOTES-7 optical afterglow candidate
  21. EP250427a: Global MASTER-Net observations report
  22. GRB 250424A: SVOM/VT optical observation
  23. Fermi-LAT gamma-ray observations of IceCube-250421A
  24. GRB 250424A: BlackGEM optical afterglow detection
  25. IceCube Alert 250421.71: Global MASTER-Net observations report
  26. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  27. EP250225a: SVOM/VT optical brightening
  28. IceCube 250414.324: DDOTI Optical Observations
  29. Fermi trigger No 766148493: Global MASTER-Net observations report
  30. Fermi trigger No 766173972: Global MASTER-Net observations report
  31. GRB 250411A: Fermi GBM Final Real-time Localization
  32. GRB 250407A: Continued KAIT/Nickel optical observations
  33. GRB 250407A: Mondy and AbAO Optical Observations
  34. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  35. IPN triangulation of GRB 250407A
  36. Fermi GRB 250407A: Global MASTER-Net observations report
  37. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  38. Fermi trigger No 765619921: Global MASTER-Net observations report
  39. GRB 250404A / EP250404a: Mondy optical observations
  40. GRB 250404A / EP250404a: NOT optical observations
  41. Fermi GRB 250404A: Global MASTER-Net observations report
  42. EP250404a: Global MASTER-Net observations report
  43. GRB 250402B: AstroSat CZTI detection of a short burst
  44. Fermi GRB 250331E: Global MASTER-Net observations report
  45. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  46. GRB 250331C: Swift detection of a burst
  47. GRB 250331A: MAXI/GSC detection
  48. Fermi GRB 250330A: Global MASTER-Net observations report
  49. IceCube Alert 250330.35: Global MASTER-Net observations report
  50. GRB 250329A: SVOM/VT optical counterpart confirmation
  51. GRB 250327B: LCO optical counterpart detection
  52. EP250321a: LCO optical counterpart detection
  53. EP250321a: Einstein Probe detection of an X-ray transient
  54. EP250226a/GRB 250226A: KAIT optical observations
  55. Fermi trigger No 763933627: Global MASTER-Net observations report
  56. Fermi GRB 250316A: Global MASTER-Net observations report
  57. GRB 250314A: Swift XRT Detection
  58. EP250315a: optical counterpart candidate detected by Gemini North
  59. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  60. Fermi GRB 250313A: Global MASTER-Net observations report
  61. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  62. GRB 250312A: Swift detection of a burst
  63. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  64. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  65. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  66. GRB 250309B / IceCube-250309A: GECAM-B observations
  67. GRB 250309B / AT2025dws: SAO RAS optical observations
  68. GRB 250309B / AT2025dws: Swift-UVOT detection
  69. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  70. GRB 250309B: Fermi GBM Observation
  71. Fermi GRB 250309B: Global MASTER-Net observations report
  72. Fermi GRB 250309A: Global MASTER-Net observations report
  73. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  74. IceCube-250309A: No candidates from the Zwicky Transient Facility
  75. Fermi-LAT gamma-ray observations of IceCube-250309A
  76. GRB 250309B: Fermi GBM Final Localization
  77. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  78. IceCube Alert 250309.32: Global MASTER-Net observations report
  79. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  80. EP250308a: Global MASTER-Net observations report
  81. Fermi GRB 250307A: Global MASTER-Net observations report
  82. Fermi trigger No 762963055: Global MASTER-Net observations report
  83. The EP-WXT trigger 01709132323 is likely a flaring star
  84. Fermi GRB 250305A: Global MASTER-Net observations report
  85. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  86. EP250302a: SAO RAS optical observations
  87. EP250302a: Nanshan/HMT optical counterpart detection
  88. GRB 250225B: VLT/HAWKI near-infrared observations
  89. EP250228a: updates on the EP observations
  90. EP250228a: Einstein Probe detection of an X-ray transient
  91. EP250225a: NOT optical candidate counterpart
  92. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  93. Fermi GRB 250225A: Global MASTER-Net observations report
  94. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  95. EP250223a: GOTO optical afterglow detections
  96. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  97. GRB 250221A: Assy optical observations
  98. EP250220a: EP-FXT follow-up observations
  99. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  100. GRB 250220A: Fermi GBM Final Real-time Localization

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