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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"

11105 results found.

  1. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  2. Fermi GRB 251002A: Global MASTER-Net observations report
  3. GRB 251001A: SVOM/GRM observation
  4. GRB 251001A: Insight-HXMT detection
  5. GRB 251001B: COLIBRÍ optical observations
  6. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  7. GRB 251001B: SVOM/VT optical observation
  8. GRB 251001B: NOT optical observations
  9. GRB 251001B: Fermi GBM Observation
  10. GRB 251001B: Further GOTO observations of optical counterpart.
  11. GRB 250930A: Fermi GBM Final Localization
  12. GRB 250930A: SVOM/GRM observation
  13. GRB 251001B: GOTO optical counterpart detection
  14. GRB 251001B: Fermi GBM Final Real-time Localization
  15. GRB 251001A: Fermi GBM Detection
  16. GRB 251001A: BALROG localization (Fermi Trigger 780979261 / GRB 251001112)
  17. GRB 251001A: Fermi GBM Final Real-time Localization
  18. Fermi GRB 250929A: Global MASTER-Net observations report
  19. GRB 250929A: Fermi GBM Final Real-time Localization
  20. GRB 250926A: CALET Gamma-Ray Burst Monitor detection
  21. GRB 250916A: SVOM/VT optical observation
  22. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  23. GRB 250926A: triangulation location with Insight-HXMT/HE and Fermi/GBM
  24. GRB 250926A: Insight-HXMT detection
  25. GRB 250926B: Fermi GBM Final Localization
  26. Fermi trigger No 780609036: Global MASTER-Net observations report
  27. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  28. GRB 250926A: AstroSat CZTI detection
  29. IceCube-250926A - IceCube observation of a high-energy neutrino candidate track-like event
  30. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  31. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  32. Fermi GRB 250926A: Global MASTER-Net observations report
  33. GRB 250926A: Fermi GBM Final Real-time Localization
  34. GRB 250922A: SVOM/GRM observation
  35. GRB 250920B: AstroSat CZTI detection
  36. GRB 250920C: Kilonova-Catcher optical afterglow detection
  37. GRB 250922B: SVOM/GRM observation
  38. GRB 250920C: TRT optical observation
  39. GRB 250924B: Fermi GBM Final Localization
  40. GRB 250919A / EP250919a: further LCO optical observation
  41. GRB 250920B: AbAO optical upper limits
  42. Konus-Wind detection of GRB 250920C
  43. GRB 250920C: KAIT optical observations
  44. GRB 250920B: CrAO ZTSH optical observations
  45. GRB 250920C: COLIBRÍ optical observations
  46. Fermi GRB 250922B: Global MASTER-Net observations report
  47. GRB 250920B: SAO RAS optical observations
  48. GRB 250920C: NIR observations with WINTER
  49. GRB 250920B: NIR observations with WINTER
  50. Fermi trigger No 780156732: Global MASTER-Net observations report
  51. GRB 250922B: Fermi GBM Final Real-time Localization
  52. GRB 250920C: PRIME near-infrared detection
  53. Konus-Wind detection of GRB 250920B
  54. Konus-Wind detection of GRB 250920A
  55. IPN triangulation of GRB 250920A (long/bright)
  56. GRB 250916A: Swift/UVOT Detection
  57. GRB 250920B: Glowbug gamma-ray detection
  58. GRB 250916A: CrAO ZTSh R-band optical observations
  59. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  60. GRB 250922A: Fermi GBM Final Localization
  61. GRB 250920B: Kitab-ISON optical upper limit
  62. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  63. GRB 250920C: SVOM/GRM observation
  64. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  65. GRB 250917B: KAIT optical upper limit
  66. GRB 250920A: NuSTAR detection of bright prompt emission
  67. GRB 250920C: GROWTH-India Telescope optical observations
  68. GRB 250916A: FTW optical and NIR observations of the counterpart
  69. GRB 250920B: Fermi GBM Observation
  70. GRB 250920A: Fermi GBM Detection
  71. GRB 250920C: Fermi GBM Observation
  72. GRB 250920B: FTW optical and NIR observations of the counterpart
  73. GRB 250920A: SVOM/GRM observation
  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: Fermi GBM Final Real-time Localization
  79. GRB 250919A / EP250919a: Insight-HXMT detection
  80. GRB 250920A: AstroSat CZTI detection
  81. GRB 250920B: Fermi GBM Final Real-time Localization
  82. GRB 250920A: BALROG localization (Fermi Trigger 780029651 / GRB 250920121)
  83. GRB 250920A: Fermi GBM Final Localization
  84. GRB 250919A/EP250919a: SVOM/VT optical observation
  85. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  86. GRB 250916A: Mondy R-band optical observations
  87. GRB 250919A: Glowbug gamma-ray detection
  88. GRB 250919A: Fermi GBM Observation
  89. Fermi GRB 250918A: Global MASTER-Net observations report
  90. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  91. GRB 250918A: SVOM/GRM observation
  92. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  93. GRB 250919A: Swift-XRT afterglow detection
  94. GRB 250919A: Fermi-LAT detection
  95. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  96. GRB 250919A: SVOM/GRM observation of a very bright GRB
  97. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  98. GRB 250916A: Fermi GBM Observation
  99. Fermi GRB 250919A: Global MASTER-Net observations report
  100. GRB 250919A: Fermi GBM Final Real-time Localization

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