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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"

35360 results found.

  1. Fermi GRB 250922B: Global MASTER-Net observations report
  2. GRB 250920B: SAO RAS optical observations
  3. GRB 250920C: NIR observations with WINTER
  4. GRB 250920B: NIR observations with WINTER
  5. GRB 250922B: Fermi GBM Final Real-time Localization
  6. GRB 250920C: PRIME near-infrared detection
  7. Konus-Wind detection of GRB 250920B
  8. Konus-Wind detection of GRB 250920A
  9. IPN triangulation of GRB 250920A (long/bright)
  10. Konus-Wind detection of GRB 250911A
  11. GRB 250916A: Swift/UVOT Detection
  12. GRB 250920B: Glowbug gamma-ray detection
  13. GRB 250916A: CrAO ZTSh R-band optical observations
  14. GRB 250920C: Swift-XRT refined Analysis
  15. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  16. GRB 250922A: Fermi GBM Final Localization
  17. GRB 250920B: Asiago optical observations
  18. GRB 250920B: Kitab-ISON optical upper limit
  19. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  20. GRB 250920C: SVOM/GRM observation
  21. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  22. GRB 250917B: KAIT optical upper limit
  23. GRB 250920A: NuSTAR detection of bright prompt emission
  24. GRB 250920C: GROWTH-India Telescope optical observations
  25. GRB 250920C: Swift-BAT refined analysis
  26. GRB 250920B: Swift-BAT refined analysis
  27. GRB 250920C: Enhanced Swift-XRT position
  28. GRB 250916A: FTW optical and NIR observations of the counterpart
  29. GRB 250920C: Swift/UVOT Detection
  30. GRB 250920B: Fermi GBM Observation
  31. GRB 250920A: Fermi GBM Detection
  32. GRB 250920C: Fermi GBM Observation
  33. Swift GRB 250920C: Global MASTER-Net observations report
  34. GRB 250920B: Swift/UVOT Detection
  35. GRB 250920B: FTW optical and NIR observations of the counterpart
  36. GRB 250920C: Optical counterpart detection by LCO
  37. GRB 250920A: SVOM/GRM observation
  38. GRB250920C: LCOGT Optical Detection
  39. GRB 250920B: Enhanced Swift-XRT position
  40. GRB 250920B: Swift-XRT refined Analysis
  41. GRB 250920B: SVOM/C-GFT optical observations
  42. GRB 250920C: GOTO optical counterpart candidate
  43. GRB 250919A / EP250919a: LCO optical observation
  44. Konus-Wind detection of GRB 250919A
  45. GRB 250920C: Swift detection of a burst
  46. GRB 250920C: Fermi GBM Final Real-time Localization
  47. Swift GRB 250920B: Global MASTER-Net observations report
  48. GRB 250919A / EP250919a: Insight-HXMT detection
  49. GRB 250920A: AstroSat CZTI detection
  50. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  51. GRB 250920B: Fermi GBM Final Real-time Localization
  52. GRB 250920A: BALROG localization (Fermi Trigger 780029651 / GRB 250920121)
  53. GRB 250920A: Fermi GBM Final Localization
  54. GRB 250919A/EP250919a: SVOM/VT optical observation
  55. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  56. GRB 250916A: Mondy R-band optical observations
  57. GRB 250919A: Glowbug gamma-ray detection
  58. GRB 250919A: Fermi GBM Observation
  59. Fermi GRB 250918A: Global MASTER-Net observations report
  60. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  61. GRB 250918A: SVOM/GRM observation
  62. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  63. GRB 250919A: Swift-XRT afterglow detection
  64. GRB 250919A: Fermi-LAT detection
  65. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  66. GRB 250919A: SVOM/GRM observation of a very bright GRB
  67. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  68. EP250919a: Einstein Probe detection of an X-ray transient
  69. GRB 250916A: Fermi GBM Observation
  70. Fermi GRB 250919A: Global MASTER-Net observations report
  71. GRB 250919A: Fermi GBM Final Real-time Localization
  72. GRB 250916A: KAIT optical observations
  73. GRB 250917B: VLT/HAWK-I near-infrared observations
  74. GRB 250916A: NuSTAR detection of the prompt emission
  75. GRB 250916A: further SAO RAS optical observations
  76. GRB 250912A: SVOM/ECLAIRs refined analysis
  77. GRB 250917B: Swift-BAT refined analysis
  78. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  79. GRB 250918A: Fermi GBM Final Real-time Localization
  80. GRB 250917B: Swift/UVOT Upper Limits
  81. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  82. GRB 250916A: Swift-XRT observations
  83. GRB 250916A: MAO/AZT-22 optical observations
  84. GRB 250916A: SAO RAS optical observations
  85. GRB 250916A : GIT optical observations
  86. GRB 250916A: Glowbug gamma-ray detection
  87. GRB250917B: WFST optical observations
  88. GRB 250916A: Swift ToO observations
  89. GRB 250917B: Fermi GBM Observation
  90. GRB 250917B: Swift-XRT observations
  91. Fermi GRB 250917B: Global MASTER-Net observations report
  92. GRB 250917B: Swift detection of a short burst
  93. GRB 250916A: GOTO optical counterpart candidate
  94. GRB 250917B: Fermi GBM Final Real-time Localization
  95. GRB 250917A: Fermi GBM Final Real-time Localization
  96. GRB 250916A: AstroSat CZTI detection of a bright long burst
  97. GRB 250910A: SVOM/ECLAIRs refined analysis
  98. Fermi GRB 250916A: Global MASTER-Net observations report
  99. GRB 250916A: Fermi GBM Final Real-time Localization
  100. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst

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