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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"

26037 results found.

  1. GRB 250925A: SVOM/GWAC-F60A upper limit
  2. GRB 250925A : MITSuME Akeno optical upper limits
  3. GRB 250925A: JinShan optical observations
  4. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  5. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  6. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  7. GRB250925A: Liverpool Telescope optical observations
  8. GRB 250925A: NOT optical afterglow candidate
  9. GRB 250925A: Leavitt Observatory optical upper limit
  10. GRB 250925A: Enhanced Swift-XRT position
  11. GRB 250924A: Swift-BAT refined analysis
  12. GRB 250925A: GROWTH-India Telescope Upper Limits
  13. GRB 250925A: Swift detection of a burst
  14. Swift GRB 250925A: Global MASTER-Net observations report
  15. GRB 250924A: 1.6m Mephisto optical upper limits
  16. GRB 250924A: NOT optical observations
  17. GRB 250924A: AstroSat CZTI detection
  18. GRB 250920B: AstroSat CZTI detection
  19. GRB 250924A: SVOM/VT optical observation
  20. GRB 250924A: Swift/UVOT Detection
  21. GRB 250924A: Swift-XRT refined Analysis
  22. GRB 250924A: Enhanced Swift-XRT position
  23. GRB 250924A: GROWTH-India Telescope Upper Limits
  24. GRB 250924A: KAIT optical observations
  25. GRB 250924A: Mondy optical observations, afterglow fading
  26. GRB 250924A: Kilonova-Catcher optical afterglow detection
  27. GRB 250920C: Kilonova-Catcher optical afterglow detection
  28. GRB 250920C: TRT optical observation
  29. GRB 250924A: COLIBRÍ optical observations
  30. Swift GRB 250924A: Global MASTER-Net observations report
  31. GRB 250919A / EP250919a: further LCO optical observation
  32. GRB 250924A: DDOTI Detection of the Optical Counterpart
  33. GRB 250924A: Swift detection of a burst with an optical counterpart
  34. GRB 250920B: AbAO optical upper limits
  35. Konus-Wind detection of GRB 250920C
  36. GRB 250920C: KAIT optical observations
  37. GRB 250920C: VLT redshift confirmation z = 1.399
  38. GRB 250920B: CrAO ZTSH optical observations
  39. GRB 250920C: SALT redshift confirmation
  40. GRB 250920C: COLIBRÍ optical observations
  41. GRB 250920C: PRIME near-infrared detection
  42. Konus-Wind detection of GRB 250920B
  43. Konus-Wind detection of GRB 250911A
  44. GRB 250916A: Swift/UVOT Detection
  45. GRB 250920B: Glowbug gamma-ray detection
  46. GRB 250920C: Swift-XRT refined Analysis
  47. GRB 250920B: Kitab-ISON optical upper limit
  48. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  49. GRB 250920C: SVOM/GRM observation
  50. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  51. GRB 250917B: KAIT optical upper limit
  52. GRB 250920C: GROWTH-India Telescope optical observations
  53. GRB 250920C: Swift-BAT refined analysis
  54. GRB 250920B: Swift-BAT refined analysis
  55. GRB 250920C: Enhanced Swift-XRT position
  56. GRB 250920C: Swift/UVOT Detection
  57. GRB 250920B: Fermi GBM Observation
  58. GRB 250920C: Fermi GBM Observation
  59. Swift GRB 250920C: Global MASTER-Net observations report
  60. GRB 250920B: Swift/UVOT Detection
  61. GRB 250920C: Optical counterpart detection by LCO
  62. GRB250920C: LCOGT Optical Detection
  63. GRB 250920B: Enhanced Swift-XRT position
  64. GRB 250920B: Swift-XRT refined Analysis
  65. GRB 250920B: SVOM/C-GFT optical observations
  66. GRB 250920C: GOTO optical counterpart candidate
  67. GRB 250920C: Swift detection of a burst
  68. Swift GRB 250920B: Global MASTER-Net observations report
  69. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  70. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  71. GRB 250916A: Mondy R-band optical observations
  72. GRB 250919A: Fermi GBM Observation
  73. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  74. GRB 250919A: Swift-XRT afterglow detection
  75. GRB 250916A: KAIT optical observations
  76. GRB 250917B: Swift-BAT refined analysis
  77. GRB 250917B: Swift/UVOT Upper Limits
  78. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  79. GRB 250916A: Swift-XRT observations
  80. GRB250917B: WFST optical observations
  81. GRB 250916A: Swift ToO observations
  82. GRB 250917B: Fermi GBM Observation
  83. GRB 250917B: Swift-XRT observations
  84. GRB 250917B: Swift detection of a short burst
  85. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  86. GRB 250912A: Swift-XRT observations
  87. GRB 250912A: VLT observations
  88. GRB 250911A: Insight-HXMT detection
  89. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  90. GRB 250911A: GECAM-B detection
  91. GRB 250911A: Swift-BAT refined analysis
  92. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  93. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  94. EP250911a: SVOM/VT optical observation
  95. GRB 250911A: MASTER optical counterpart observations
  96. GRB 250911A: Swift-XRT refined Analysis
  97. EP250911a: Swift-XRT observations
  98. GRB 250911A: Swift/UVOT Detection
  99. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  100. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation

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