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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. EP250421A: COLIBRÍ Optical Upper Limit
  2. GRB 250419A: Mondy Continued Optical Observations
  3. Fermi GRB 250421A: Global MASTER-Net observations report
  4. EP250421a: Global MASTER-Net observations report
  5. GRB 250421B: AstroSat CZTI detection of a bright long burst
  6. EP250421a: Einstein Probe detection of an X-ray transient
  7. EP250421a: Mephisto optical counterpart confirmation
  8. IceCube Alert 250421.71: Global MASTER-Net observations report
  9. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  10. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  11. EP250421a: JinShan likely optical counterpart
  12. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  13. GRB 250421A: Fermi GBM Final Real-time Localization
  14. GRB 250419A: Liverpool Telescope observations
  15. GRB 250419A: LCO optical observation
  16. GRB 250419A: JinShan optical observations
  17. GRB 250419A: SVOM/VT optical continuous observations
  18. GRB 250419A: SVOM/C-GFT optical observations
  19. GRB 250419A: Swift/UVOT Follow up
  20. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  21. GRB 250419A: LCO optical afterglow multi-band observations
  22. GRB 250419A: Mondy and AbAO Optical Observations
  23. GRB 250419A: Liverpool Telescope observations
  24. GRB 250419A: AKO Optical Afterglow Detection
  25. GRB 250419A: MASTER optical afterglow observation
  26. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  27. GRB 250407A: rest-frame energetics from Konus-Wind observation
  28. GRB 250419A: Swift-XRT localisation
  29. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  30. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  31. GRB 250419A: Swift-XRT refined Analysis
  32. GRB 250419A: GOTO optical counterpart detection
  33. GRB 250419A: KAIT optical afterglow observations
  34. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  35. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  36. GRB 250419A: SVOM detection of a soft burst
  37. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  38. EP250416a: Swift/XRT counterpart fading
  39. EP250416a: refined EP-WXT and EP-FXT analysis
  40. Konus-Wind detection of GRB 250403A
  41. EP20250416a: Swift/XRT counterpart detection
  42. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  43. IceCube-250416A: DDOTI Optical Observations
  44. EP250416a: Gemini South-GMOS optical counterpart
  45. EP250225a: SVOM/VT optical brightening
  46. SVOM/sb25041603 is not a GRB
  47. EP250416a: GSP optical upper limit
  48. EP250416a: Global MASTER-Net observations report
  49. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  50. EP250416a: Einstein Probe detection of an X-ray transient
  51. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  52. IceCube-250416A: Global MASTER-Net observations report
  53. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  54. GRB 250416B: Fermi GBM Final Real-time Localization
  55. GRB 250416A: Fermi GBM Final Real-time Localization
  56. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  57. SVOM/sb25041603: SVOM detection of an X-ray transient
  58. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  59. IceCube 250414.324: DDOTI Optical Observations
  60. GRB 250413A: AstroSat CZTI detection
  61. EP250304a: ATCA radio observations
  62. GRB 250412A: AstroSat CZTI detection
  63. EP250404a: Nanshan 0.43m Telescope optical observatios
  64. Fermi trigger No 766148493: Global MASTER-Net observations report
  65. Fermi trigger No 766173972: Global MASTER-Net observations report
  66. GRB 250411A: DDOTI Optical Observations
  67. Fermi GRB 250411A: Global MASTER-Net observations report
  68. GRB 250411A: Fermi GBM Final Real-time Localization
  69. GRB 250407A: Continued KAIT/Nickel optical observations
  70. GRB 250314A: e-MERLIN observations
  71. GRB 250407A: Mondy and AbAO Optical Observations
  72. EP250227a: Further NOT optical observations
  73. GRB 250320B: cubesat Avion detection
  74. IceCube-250406A: Swift-XRT observations
  75. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  76. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  77. IPN triangulation of GRB 250407A
  78. EP250407a: Global MASTER-Net observations report
  79. GRB 250407A: LCO detection of a fading optical counterpart
  80. Fermi-LAT gamma-ray observations of IceCube-250406A
  81. EP250407a: Swift-XRT observations
  82. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  83. Konus-Wind detection of GRB 250407A
  84. GRB 250407A: SVOM/GRM observation of a bright long burst
  85. GRB 250407A: EP-WXT afterglow detection
  86. EP250407a: EP-WXT detection of a fast X-ray transient
  87. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  88. GRB 250407A: KAIT Optical Afterglow Candidate
  89. IceCube-250406A: No candidates from the Zwicky Transient Facility
  90. GRB 250407A: Fermi GBM Detection
  91. GRB 250407A: Swift-XRT afterglow detection
  92. Fermi GRB 250407A: Global MASTER-Net observations report
  93. GRB 250407A: Swift ToO observations
  94. GRB 250407A: SRG/ART-XC afterglow detection
  95. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  96. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  97. Konus-Wind detection of GRB 250406B (short/hard)
  98. IPN triangulation of GRB 250406B (short/hard)
  99. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  100. GRB 250407A: Fermi GBM Final Real-time Localization

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