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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.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

11757 results found.

  1. GRB 250512B: SVOM detection of a burst
  2. EP250512a: Einstein Probe detection of an X-ray transient
  3. EP250511a: Einstein Probe follow-up obsevation and refined analysis
  4. EP250511a: Global MASTER-Net observations report
  5. EP250511a: Einstein Probe detection of an X-ray transient
  6. Fermi GRB 250510C: Global MASTER-Net observations report
  7. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  8. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  9. GRB 250509A: Swift-XRT refined Analysis
  10. GRB 250510A: SVOM possible detection of a burst
  11. Fermi GRB 250509A: Global MASTER-Net observations report
  12. GRB 250509A: Swift detection of a burst
  13. EP250508a: refined analysis of the EP-WXT and EP-FXT observations
  14. GRB 250506A: Swift-XRT afterglow detection
  15. EP250508a: Global MASTER-Net observations report
  16. EP250508a: Einstein Probe detection of an X-ray transient
  17. GRB 250507A: refined SVOM/MXT data analysis
  18. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  19. IceCube Alert 250506.59: Global MASTER-Net observations report
  20. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  21. GRB 250506A: REM optical/NIR upper limits
  22. GRB 250506A: Fermi GBM Observation
  23. GRB 250504A: Swift-BAT refined analysis
  24. GRB 250504A: REM optical/NIR observations
  25. GRB 250504A: MeerLICHT optical afterglow detection
  26. Fermi GRB 250504A: Global MASTER-Net observations report
  27. GRB 250504A: Swift detection of a burst
  28. GRB 250502A: Mondy and Tien-Shan Optical Observations
  29. GRB 250502A: Montarrenti Observatory optical detection
  30. GRB 250502A: Swift-XRT afterglow detection
  31. GRB 250502B: AstroSat CZTI detection
  32. GRB 250502A: LCO optical counterpart detection
  33. GRB 250502C: Fermi GBM Final Localization
  34. GRB 250407A: VZLUSAT-2 detection
  35. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  36. GRB 250502B: DDOTI Optical Observations
  37. GRB 250430A: Swift-XRT refined Analysis
  38. GRB 250430A: Swift/UVOT Detection
  39. Fermi GRB 250502B: Global MASTER-Net observations report
  40. GRB 250430A: Swift detection of a burst with optical counterpart
  41. EP250428b: refined analysis of the EP-FXT follow-up observation
  42. EP250428b: SAO RAS optical upper limit
  43. EP250428b: Einstein Probe detection of a fast X-ray transient
  44. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  45. EP250427a: REM optical/NIR afterglow detection
  46. EP250427a: Einstein Probe detection of a fast X-ray transient
  47. IceCube Alert 250426.74: Global MASTER-Net observations report
  48. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  49. Konus-Wind detection of GRB 250424A
  50. Fermi-LAT gamma-ray observations of IceCube-250421A
  51. GRB 250424A: Kilonova-Catcher optical afterglow detection
  52. GRB 250404A / EP250404a: GRBAlpha detection
  53. GRB 250424A: Swift-XRT refined Analysis
  54. GRB 250424A: AstroSat CZTI detection of a bright long burst
  55. GRB 250424A: DDOTI Afterglow Detection
  56. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  57. SVOM/sb25042207: BOOTES-2 early optical upper limit
  58. SVOM/sb25042207: GOTO optical upper limits
  59. GRB 250421A: AstroSat CZTI detection
  60. GRB 250419A: Mephisto Multi-band Optical Detection
  61. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  62. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  63. GRB 250419A: Mondy Continued Optical Observations
  64. Fermi GRB 250421A: Global MASTER-Net observations report
  65. GRB 250421B: AstroSat CZTI detection of a bright long burst
  66. IceCube Alert 250421.71: Global MASTER-Net observations report
  67. GRB 250419A: Liverpool Telescope observations
  68. GRB 250419A: JinShan optical observations
  69. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  70. GRB 250419A: LCO optical afterglow multi-band observations
  71. GRB 250419A: MASTER optical afterglow observation
  72. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  73. GRB 250419A: Swift-XRT refined Analysis
  74. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  75. EP250416a: refined EP-WXT and EP-FXT analysis
  76. Konus-Wind detection of GRB 250403A
  77. IceCube-250416A: DDOTI Optical Observations
  78. EP250416a: GSP optical upper limit
  79. EP250416a: Global MASTER-Net observations report
  80. EP250416a: Einstein Probe detection of an X-ray transient
  81. IceCube-250416A: Global MASTER-Net observations report
  82. GRB 250413A: AstroSat CZTI detection
  83. GRB 250412A: AstroSat CZTI detection
  84. EP250404a: Nanshan 0.43m Telescope optical observatios
  85. Fermi trigger No 766148493: Global MASTER-Net observations report
  86. Fermi trigger No 766173972: Global MASTER-Net observations report
  87. Fermi GRB 250411A: Global MASTER-Net observations report
  88. GRB 250320B: cubesat Avion detection
  89. Fermi-LAT gamma-ray observations of IceCube-250406A
  90. Konus-Wind detection of GRB 250407A
  91. GRB 250407A: EP-WXT afterglow detection
  92. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  93. GRB 250407A: Fermi GBM Detection
  94. GRB 250407A: Swift-XRT afterglow detection
  95. Fermi GRB 250407A: Global MASTER-Net observations report
  96. GRB 250407A: SRG/ART-XC afterglow detection
  97. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  98. Konus-Wind detection of GRB 250406B (short/hard)
  99. GRB 250406A: AstroSat CZTI detection
  100. Fermi trigger No 765663719: Global MASTER-Net observations report

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