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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"
  1. IceCube Alert 250421.71: Global MASTER-Net observations report
  2. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  3. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  4. EP250421a: JinShan likely optical counterpart
  5. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  6. GRB 250421A: Fermi GBM Final Real-time Localization
  7. GRB 250419A: Liverpool Telescope observations
  8. GRB 250419A: LCO optical observation
  9. GRB 250419A: JinShan optical observations
  10. GRB 250419A: SVOM/VT optical continuous observations
  11. GRB 250419A: SVOM/C-GFT optical observations
  12. GRB 250419A: Swift/UVOT Follow up
  13. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  14. GRB 250419A: LCO optical afterglow multi-band observations
  15. GRB 250419A: Mondy and AbAO Optical Observations
  16. GRB 250419A: Liverpool Telescope observations
  17. GRB 250419A: AKO Optical Afterglow Detection
  18. GRB 250419A: MASTER optical afterglow observation
  19. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  20. GRB 250407A: rest-frame energetics from Konus-Wind observation
  21. GRB 250419A: Swift-XRT localisation
  22. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  23. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  24. GRB 250419A: Swift-XRT refined Analysis
  25. GRB 250419A: GOTO optical counterpart detection
  26. GRB 250419A: KAIT optical afterglow observations
  27. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  28. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  29. GRB 250419A: SVOM detection of a soft burst
  30. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  31. EP250416a: Swift/XRT counterpart fading
  32. EP250416a: refined EP-WXT and EP-FXT analysis
  33. Konus-Wind detection of GRB 250403A
  34. EP20250416a: Swift/XRT counterpart detection
  35. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  36. IceCube-250416A: DDOTI Optical Observations
  37. EP250416a: Gemini South-GMOS optical counterpart
  38. EP250225a: SVOM/VT optical brightening
  39. SVOM/sb25041603 is not a GRB
  40. EP250416a: GSP optical upper limit
  41. EP250416a: Global MASTER-Net observations report
  42. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  43. EP250416a: Einstein Probe detection of an X-ray transient
  44. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  45. IceCube-250416A: Global MASTER-Net observations report
  46. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  47. GRB 250416B: Fermi GBM Final Real-time Localization
  48. GRB 250416A: Fermi GBM Final Real-time Localization
  49. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  50. SVOM/sb25041603: SVOM detection of an X-ray transient
  51. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  52. IceCube 250414.324: DDOTI Optical Observations
  53. GRB 250413A: AstroSat CZTI detection
  54. EP250304a: ATCA radio observations
  55. GRB 250412A: AstroSat CZTI detection
  56. EP250404a: Nanshan 0.43m Telescope optical observatios
  57. Fermi trigger No 766148493: Global MASTER-Net observations report
  58. Fermi trigger No 766173972: Global MASTER-Net observations report
  59. GRB 250411A: DDOTI Optical Observations
  60. Fermi GRB 250411A: Global MASTER-Net observations report
  61. GRB 250411A: Fermi GBM Final Real-time Localization
  62. GRB 250407A: Continued KAIT/Nickel optical observations
  63. GRB 250314A: e-MERLIN observations
  64. GRB 250407A: Mondy and AbAO Optical Observations
  65. EP250227a: Further NOT optical observations
  66. GRB 250320B: cubesat Avion detection
  67. IceCube-250406A: Swift-XRT observations
  68. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  69. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  70. IPN triangulation of GRB 250407A
  71. EP250407a: Global MASTER-Net observations report
  72. GRB 250407A: LCO detection of a fading optical counterpart
  73. Fermi-LAT gamma-ray observations of IceCube-250406A
  74. EP250407a: Swift-XRT observations
  75. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  76. Konus-Wind detection of GRB 250407A
  77. GRB 250407A: SVOM/GRM observation of a bright long burst
  78. GRB 250407A: EP-WXT afterglow detection
  79. EP250407a: EP-WXT detection of a fast X-ray transient
  80. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  81. GRB 250407A: KAIT Optical Afterglow Candidate
  82. IceCube-250406A: No candidates from the Zwicky Transient Facility
  83. GRB 250407A: Fermi GBM Detection
  84. GRB 250407A: Swift-XRT afterglow detection
  85. Fermi GRB 250407A: Global MASTER-Net observations report
  86. GRB 250407A: Swift ToO observations
  87. GRB 250407A: SRG/ART-XC afterglow detection
  88. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  89. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  90. Konus-Wind detection of GRB 250406B (short/hard)
  91. IPN triangulation of GRB 250406B (short/hard)
  92. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  93. GRB 250407A: Fermi GBM Final Real-time Localization
  94. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  95. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  96. IceCube 250406.951: DDOTI Optical Observations
  97. GRB 250406A: AstroSat CZTI detection
  98. IceCube Alert 250406.95: Global MASTER-Net observations report
  99. Fermi trigger No 765663719: Global MASTER-Net observations report
  100. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14

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