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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.

Advanced Search Examples (click to copy):

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

39182 results found.

  1. GRB 250924A: 1.6m Mephisto optical upper limits
  2. GRB 250924A: SAO RAS optical observations
  3. GRB 250924A: NOT optical observations
  4. GRB 250924A: AstroSat CZTI detection
  5. GRB 250914A: AstroSat CZTI detection
  6. GRB 250920B: AstroSat CZTI detection
  7. GRB 250924A: SVOM/VT optical observation
  8. GRB 250924A: Swift/UVOT Detection
  9. GRB 250924A: Swift-XRT refined Analysis
  10. GRB 250924A: Enhanced Swift-XRT position
  11. GRB 250924A: J-band detection with WINTER
  12. GRB 250924A: GROWTH-India Telescope Upper Limits
  13. GRB 250924A: KAIT optical observations
  14. GRB 250924A: Mondy optical observations, afterglow fading
  15. GRB 250924A: Kilonova-Catcher optical afterglow detection
  16. GRB 250920C: Kilonova-Catcher optical afterglow detection
  17. GRB 250922B: SVOM/GRM observation
  18. GRB 250920C: TRT optical observation
  19. GRB 250924B: Fermi GBM Final Localization
  20. GRB 250924A: COLIBRÍ optical observations
  21. Swift GRB 250924A: Global MASTER-Net observations report
  22. GRB 250919A / EP250919a: further LCO optical observation
  23. GRB 250924A: DDOTI Detection of the Optical Counterpart
  24. GRB 250924A: Swift detection of a burst with an optical counterpart
  25. GRB 250920B: AbAO optical upper limits
  26. Konus-Wind detection of GRB 250920C
  27. GRB 250920C: KAIT optical observations
  28. GRB 250920C: VLT redshift confirmation z = 1.399
  29. GRB 250920B: CrAO ZTSH optical observations
  30. GRB 250920C: SALT redshift confirmation
  31. GRB 250920C: COLIBRÍ optical observations
  32. GRB 250922C: AstroSat CZTI detection of a short burst
  33. Fermi GRB 250922B: Global MASTER-Net observations report
  34. GRB 250920B: SAO RAS optical observations
  35. GRB 250920C: NIR observations with WINTER
  36. GRB 250920B: NIR observations with WINTER
  37. Fermi trigger No 780156732: Global MASTER-Net observations report
  38. GRB 250922B: Fermi GBM Final Real-time Localization
  39. GRB 250920C: PRIME near-infrared detection
  40. Konus-Wind detection of GRB 250920B
  41. Konus-Wind detection of GRB 250920A
  42. IPN triangulation of GRB 250920A (long/bright)
  43. Konus-Wind detection of GRB 250911A
  44. GRB 250916A: Swift/UVOT Detection
  45. GRB 250920B: Glowbug gamma-ray detection
  46. GRB 250916A: CrAO ZTSh R-band optical observations
  47. GRB 250920C: Swift-XRT refined Analysis
  48. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  49. GRB 250922A: Fermi GBM Final Localization
  50. GRB 250920B: Asiago optical observations
  51. GRB 250920B: Kitab-ISON optical upper limit
  52. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  53. GRB 250920C: SVOM/GRM observation
  54. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  55. GRB 250917B: KAIT optical upper limit
  56. GRB 250920A: NuSTAR detection of bright prompt emission
  57. GRB 250920C: GROWTH-India Telescope optical observations
  58. GRB 250920C: Swift-BAT refined analysis
  59. GRB 250920B: Swift-BAT refined analysis
  60. GRB 250920C: Enhanced Swift-XRT position
  61. GRB 250916A: FTW optical and NIR observations of the counterpart
  62. GRB 250920C: Swift/UVOT Detection
  63. GRB 250920B: Fermi GBM Observation
  64. GRB 250920A: Fermi GBM Detection
  65. GRB 250920C: Fermi GBM Observation
  66. Swift GRB 250920C: Global MASTER-Net observations report
  67. GRB 250920B: Swift/UVOT Detection
  68. GRB 250920B: FTW optical and NIR observations of the counterpart
  69. GRB 250920C: Optical counterpart detection by LCO
  70. GRB 250920A: SVOM/GRM observation
  71. GRB250920C: LCOGT Optical Detection
  72. GRB 250920B: Enhanced Swift-XRT position
  73. GRB 250920B: Swift-XRT refined Analysis
  74. GRB 250920B: SVOM/C-GFT optical observations
  75. GRB 250920C: GOTO optical counterpart candidate
  76. GRB 250919A / EP250919a: LCO optical observation
  77. Konus-Wind detection of GRB 250919A
  78. GRB 250920C: Swift detection of a burst
  79. GRB 250920C: Fermi GBM Final Real-time Localization
  80. Swift GRB 250920B: Global MASTER-Net observations report
  81. GRB 250919A / EP250919a: Insight-HXMT detection
  82. GRB 250920A: AstroSat CZTI detection
  83. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  84. GRB 250920B: Fermi GBM Final Real-time Localization
  85. GRB 250920A: BALROG localization (Fermi Trigger 780029651 / GRB 250920121)
  86. GRB 250920A: Fermi GBM Final Localization
  87. GRB 250919A/EP250919a: SVOM/VT optical observation
  88. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  89. GRB 250916A: Mondy R-band optical observations
  90. GRB 250919A: Glowbug gamma-ray detection
  91. GRB 250919A: Fermi GBM Observation
  92. Fermi GRB 250918A: Global MASTER-Net observations report
  93. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  94. GRB 250918A: SVOM/GRM observation
  95. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  96. GRB 250919A: Swift-XRT afterglow detection
  97. GRB 250919A: Fermi-LAT detection
  98. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  99. GRB 250919A: SVOM/GRM observation of a very bright GRB
  100. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)

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