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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"

14824 results found.

  1. GRB 250926B: Fermi GBM Final Localization
  2. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  3. GRB 250926A: AstroSat CZTI detection
  4. GRB 250925A: COLIBRÍ photometric redshift
  5. IceCube-250926A - IceCube observation of a high-energy neutrino candidate track-like event
  6. GRB 250925A/EP250925a: EP-WXT detection
  7. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  8. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  9. GRB 250926A: Fermi GBM Final Real-time Localization
  10. GRB250925A: Liverpool Telescope optical observations
  11. GRB 250925A: Swift detection of a burst
  12. GRB 250924A: AstroSat CZTI detection
  13. GRB 250914A: AstroSat CZTI detection
  14. GRB 250920B: AstroSat CZTI detection
  15. GRB 250924A: Swift/UVOT Detection
  16. GRB 250924A: J-band detection with WINTER
  17. GRB 250924A: Mondy optical observations, afterglow fading
  18. GRB 250924A: Kilonova-Catcher optical afterglow detection
  19. GRB 250920C: Kilonova-Catcher optical afterglow detection
  20. GRB 250920C: TRT optical observation
  21. GRB 250924B: Fermi GBM Final Localization
  22. GRB 250924A: DDOTI Detection of the Optical Counterpart
  23. GRB 250924A: Swift detection of a burst with an optical counterpart
  24. Konus-Wind detection of GRB 250920C
  25. GRB 250920C: VLT redshift confirmation z = 1.399
  26. GRB 250922C: AstroSat CZTI detection of a short burst
  27. GRB 250922B: Fermi GBM Final Real-time Localization
  28. GRB 250920C: PRIME near-infrared detection
  29. Konus-Wind detection of GRB 250920B
  30. Konus-Wind detection of GRB 250920A
  31. IPN triangulation of GRB 250920A (long/bright)
  32. Konus-Wind detection of GRB 250911A
  33. GRB 250916A: Swift/UVOT Detection
  34. GRB 250920B: Glowbug gamma-ray detection
  35. GRB 250922A: Fermi GBM Final Localization
  36. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  37. GRB 250920A: NuSTAR detection of bright prompt emission
  38. GRB 250920C: Swift/UVOT Detection
  39. GRB 250920A: Fermi GBM Detection
  40. GRB 250920B: Swift/UVOT Detection
  41. GRB 250920C: Optical counterpart detection by LCO
  42. GRB250920C: LCOGT Optical Detection
  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. GRB 250919A / EP250919a: Insight-HXMT detection
  48. GRB 250920A: AstroSat CZTI detection
  49. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  50. GRB 250920B: Fermi GBM Final Real-time Localization
  51. GRB 250920A: Fermi GBM Final Localization
  52. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  53. GRB 250919A: Glowbug gamma-ray detection
  54. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  55. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  56. GRB 250919A: Swift-XRT afterglow detection
  57. GRB 250919A: Fermi-LAT detection
  58. EP250919a: Einstein Probe detection of an X-ray transient
  59. GRB 250919A: Fermi GBM Final Real-time Localization
  60. GRB 250916A: NuSTAR detection of the prompt emission
  61. GRB 250918A: Fermi GBM Final Real-time Localization
  62. EP250916a: EP-FXT follow-up observation
  63. GRB 250916A: Glowbug gamma-ray detection
  64. GRB250917B: WFST optical observations
  65. GRB 250917B: Swift detection of a short burst
  66. GRB 250916A: GOTO optical counterpart candidate
  67. GRB 250917B: Fermi GBM Final Real-time Localization
  68. GRB 250917A: Fermi GBM Final Real-time Localization
  69. GRB 250916A: AstroSat CZTI detection of a bright long burst
  70. EP250916a: Einstein Probe detection of an X-ray transient
  71. GRB 250916A: Fermi GBM Final Real-time Localization
  72. SVOM/sb25091517: SVOM detection of an X-ray transient
  73. GRB 250912A: VLT observations
  74. GRB 250911A: Insight-HXMT detection
  75. GRB 250912A: SVOM detection of a burst
  76. GRB 250912A: Fermi GBM Final Real-time Localization
  77. GRB 250911A: GECAM-B detection
  78. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  79. GRB 250910C: Fermi GBM Final Localization Correction
  80. EP250911a: Optical detection with Kinder observations
  81. GRB 250911A: Swift/UVOT Detection
  82. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  83. GRB 250909B: Insight-HXMT detection
  84. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  85. EP250911a: LCO optical counterpart discovery
  86. EP250911a: Einstein Probe detection of an X-ray transient
  87. GRB 250911A: Swift detection of a burst
  88. GRB 250910B: Fermi GBM Final Real-time Localization
  89. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  90. GRB 250909B: AstroSat CZTI detection of a long burst
  91. GRB 250909A: AstroSat CZTI detection
  92. GRB 250910A: SVOM/MXT possible afterglow detection
  93. GRB 250910A: SVOM detection of a faint burst
  94. LIGO/Virgo/KAGRA S250910b: Retraction of GW compact binary merger candidate
  95. EP250908b/EP#01709240653: Swift/UVOT Detection
  96. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  97. EP250908c: Einstein Probe detection of an X-ray transient
  98. GRB 250909A: Fermi GBM Final Real-time Localization
  99. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  100. GRB 250907A: GECAM-B detection

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