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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"

19549 results found.

  1. GRB 250925A: Enhanced Swift-XRT position
  2. GRB 250925A: GROWTH-India Telescope Upper Limits
  3. GRB 250922A: SVOM/GRM observation
  4. GRB 250924A: 1.6m Mephisto optical upper limits
  5. GRB 250924A: SAO RAS optical observations
  6. GRB 250914A: AstroSat CZTI detection
  7. GRB 250920B: AstroSat CZTI detection
  8. GRB 250924A: SVOM/VT optical observation
  9. GRB 250924A: Swift/UVOT Detection
  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: Mondy optical observations, afterglow fading
  14. GRB 250924A: Kilonova-Catcher optical afterglow detection
  15. GRB 250920C: Kilonova-Catcher optical afterglow detection
  16. GRB 250922B: SVOM/GRM observation
  17. GRB 250920C: TRT optical observation
  18. GRB 250924A: COLIBRÍ optical observations
  19. GRB 250919A / EP250919a: further LCO optical observation
  20. GRB 250924A: DDOTI Detection of the Optical Counterpart
  21. GRB 250924A: Swift detection of a burst with an optical counterpart
  22. GRB 250920B: AbAO optical upper limits
  23. GRB 250920C: KAIT optical observations
  24. GRB 250920B: CrAO ZTSH optical observations
  25. GRB 250920C: COLIBRÍ optical observations
  26. GRB 250922C: AstroSat CZTI detection of a short burst
  27. GRB 250920B: SAO RAS optical observations
  28. GRB 250920C: NIR observations with WINTER
  29. GRB 250920B: NIR observations with WINTER
  30. GRB 250920C: PRIME near-infrared detection
  31. GRB 250916A: Swift/UVOT Detection
  32. GRB 250916A: CrAO ZTSh R-band optical observations
  33. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  34. GRB 250920B: Asiago optical observations
  35. GRB 250920B: Kitab-ISON optical upper limit
  36. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  37. GRB 250920C: SVOM/GRM observation
  38. GRB 250920C: GROWTH-India Telescope optical observations
  39. GRB 250920C: Enhanced Swift-XRT position
  40. GRB 250920C: Swift/UVOT Detection
  41. GRB 250920B: Swift/UVOT Detection
  42. GRB 250920C: Optical counterpart detection by LCO
  43. GRB 250920A: SVOM/GRM observation
  44. GRB250920C: LCOGT Optical Detection
  45. GRB 250920B: Enhanced Swift-XRT position
  46. GRB 250920B: SVOM/C-GFT optical observations
  47. GRB 250919A / EP250919a: LCO optical observation
  48. GRB 250920C: Swift detection of a burst
  49. GRB 250919A / EP250919a: Insight-HXMT detection
  50. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  51. GRB 250919A/EP250919a: SVOM/VT optical observation
  52. GRB 250916A: Mondy R-band optical observations
  53. GRB 250918A: SVOM/GRM observation
  54. GRB 250919A: Swift-XRT afterglow detection
  55. GRB 250919A: SVOM/GRM observation of a very bright GRB
  56. EP250919a: Einstein Probe detection of an X-ray transient
  57. GRB 250916A: KAIT optical observations
  58. GRB 250917B: VLT/HAWK-I near-infrared observations
  59. GRB 250916A: further SAO RAS optical observations
  60. GRB 250912A: SVOM/ECLAIRs refined analysis
  61. GRB 250917B: Swift/UVOT Upper Limits
  62. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  63. GRB 250916A: MAO/AZT-22 optical observations
  64. GRB 250916A: SAO RAS optical observations
  65. GRB 250916A : GIT optical observations
  66. GRB250917B: WFST optical observations
  67. GRB 250916A: Swift ToO observations
  68. GRB 250917B: Swift detection of a short burst
  69. EP250916a: Einstein Probe detection of an X-ray transient
  70. SVOM/sb25091517: SVOM detection of an X-ray transient
  71. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  72. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  73. GRB250912A: VLT/HAWK-I follow-up observations
  74. GRB 250912A:SVOM/VT optical upper limit
  75. GRB 250912A: LCO optical upper limit
  76. GRB 250912A: SVOM detection of a burst
  77. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  78. GRB 250910B: SVOM/GRM observation
  79. EP250911a: SVOM/VT optical observation
  80. EP250911a: SAO RAS optical observations
  81. EP250911a: Optical detection with Kinder observations
  82. GRB 250911A: Swift/UVOT Detection
  83. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  84. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  85. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  86. EP250911a: COLIBRÍ optical observations
  87. EP250911a: Einstein Probe detection of an X-ray transient
  88. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  89. GRB 250911A: Enhanced Swift-XRT position
  90. GRB 250911A: Swift-XRT observations
  91. GRB 250911A: COLIBRÍ optical counterpart candidate
  92. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  93. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  94. GRB 250909B: AstroSat CZTI detection of a long burst
  95. GRB 250910A: SVOM/VT optical upper limit
  96. GRB 250910A: LCO optical upper limit
  97. GRB 250910A: SVOM detection of a faint burst
  98. EP250908b/EP#01709240653: Swift/UVOT Detection
  99. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  100. EP250908c: SVOM/VT optical observation

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