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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"

14817 results found.

  1. GRB 251010A: AstroSat CZTI detection
  2. GRB 251011A: AstroSat CZTI detection
  3. GRB 251009B: SVOM/GRM observation of short GRB
  4. GRB 251011B: Swift detection of a burst
  5. GRB 251011B: Fermi GBM Final Real-time Localization
  6. GRB 251011A: Fermi GBM Final Real-time Localization
  7. GRB 251010A: Fermi GBM Final Real-time Localization
  8. GRB251007A: Swift/UVOT Detection
  9. GRB 251009A: GECAM-B detection of a short burst
  10. GRB 251009A: Insight-HXMT detection of a short burst
  11. GRB 251009B (short): Glowbug gamma-ray detection
  12. GRB 251009B: Insight-HXMT detection of a short burst
  13. GRB 251007A: Insight-HXMT detection
  14. GRB 251006A: CALET Gamma-Ray Burst Monitor detection
  15. SVOM/sb25101004: SVOM detection of a stellar flare
  16. GRB 251009A: Fermi GBM Final Localization
  17. GRB 250916A: TERI Gamma-ray detection
  18. GRB 250919A: TERI gamma-ray detection
  19. GRB 251007A: 1.5m OSN and 2.2m CAHA optical follow-up
  20. IceCube alert 141456_888784 retraction
  21. GRB 251007A: AstroSat CZTI detection
  22. GRB 251006B/EP251006a: EP-FXT afterglow detection
  23. GRB 251007A: NOT optical observations
  24. GRB 251007A: CALET Gamma-Ray Burst Monitor detection
  25. GRB 251006B: Insight-HXMT detection
  26. GRB 251005C: PRIME J-band upper limit
  27. GRB 251007A: Glowbug gamma-ray detection
  28. GRB 251007B: SVOM detection of a faint burst
  29. GRB 251007B: Swift detection of a burst
  30. GRB 251007A: Swift detection of a burst with an optical counterpart
  31. GRB 251006A: Swift/BAT-GUANO subthreshold detection of a short burst
  32. GRB 251005B: Glowbug gamma-ray detection
  33. GRB 251006B/EP251006a: EP-FXT follow-up observation
  34. GRB 251006B/EP251006a: EP-WXT detection
  35. GRB 251006B: Fermi GBM Final Real-time Localization
  36. GRB 251006A (short): Glowbug gamma-ray detection
  37. GRB 251005C: COLIBRÍ optical observations
  38. GRB 251003A: LAST optical observations
  39. GRB 251002A: LAST optical observations
  40. GRB 251006A: Fermi GBM Final Real-time Localization
  41. GRB 251005C: AstroSat CZTI detection
  42. GRB 250902A: MSU cubesats detection
  43. GRB 251005C: Swift detection of a burst
  44. GRB 251005B: Fermi GBM Final Real-time Localization
  45. GRB 251005A: Fermi GBM Final Localization
  46. GRB 251002A: Insight-HXMT detection
  47. GRB 251002A: Insight-HXMT detection
  48. EP251003a: Einstein Probe detection of an X-ray transient
  49. GRB 251003A: J-band detection with WINTER
  50. Fermi GBM Sub-Threshold Detection of GRB 250910A
  51. GRB 251002A: Swift/UVOT detection
  52. GRB 251001A: AstroSat CZTI detection
  53. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  54. GRB 251003A: GOTO detection of the optical counterpart
  55. LIGO/Virgo/KAGRA S251003at: Retraction of GW compact binary merger candidate
  56. GRB 251002A: GOTO detection of optical counterpart
  57. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  58. GRB 251002A: AKO Early Optical Afterglow Detection
  59. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  60. GRB 251003A: Kilonova-Catcher optical afterglow detection
  61. GRB 251002A: Swift-XRT afterglow detection
  62. GRB 251002A: Kilonova-Catcher optical afterglow detection
  63. GRB 251001C: CALET Gamma-Ray Burst Monitor detection
  64. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  65. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  66. GRB 251002A: EP-FXT counterpart detection
  67. GRB 251003A: LCOGT Optical Detection
  68. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  69. GRB 251003A: 1.5m OSN afterglow candidate
  70. GRB 251003A: Swift detection of a burst
  71. GRB 251003A: Fermi GBM Final Real-time Localization
  72. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  73. GRB 251002A: BOOTES-6 early optical detection
  74. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  75. GRB 251002A: FRAM-ORM afterglow detection
  76. GRB 251002A: SVOM detection of a burst
  77. GRB 251001A: SVOM/GRM observation
  78. GRB 251001A: Insight-HXMT detection
  79. GRB 251001B: Swift/UVOT Detection
  80. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  81. GRB 251001C: Glowbug gamma-ray detection
  82. GRB 251001B: Further GOTO observations of optical counterpart.
  83. GRB 250930A: Fermi GBM Final Localization
  84. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  85. GRB 251001B: GOTO optical counterpart detection
  86. GRB 251001B: Swift detection of a burst
  87. GRB 251001B: Fermi GBM Final Real-time Localization
  88. GRB 251001A: Fermi GBM Detection
  89. GRB 251001A: Fermi GBM Final Real-time Localization
  90. GRB 250929A: Fermi GBM Final Real-time Localization
  91. GRB 250926A: CALET Gamma-Ray Burst Monitor detection
  92. GRB 250926A: triangulation location with Insight-HXMT/HE and Fermi/GBM
  93. GRB 250926A: Insight-HXMT detection
  94. GRB 250926B: Fermi GBM Final Localization
  95. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  96. GRB 250926A: AstroSat CZTI detection
  97. GRB 250925A: COLIBRÍ photometric redshift
  98. IceCube-250926A - IceCube observation of a high-energy neutrino candidate track-like event
  99. GRB 250925A/EP250925a: EP-WXT detection
  100. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+

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