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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"

28068 results found.

  1. GRB 260424B: SVOM/GRM detection of a short burst
  2. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  3. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  4. GRB 260401A: cubesat Avion detection
  5. GRB 260424A: AstroSat CZTI detection of a long burst
  6. GRB 260421B: Kilonova-Catcher optical afterglow detection
  7. GRB 260421B: Insight-HXMT/HE detection
  8. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  9. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  10. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  11. GRB 260419A: AstroSat CZTI detection
  12. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  13. GOTO26djh/AT2026jpw: ATCA radio detection
  14. GRB 260421B: LCO optical counterpart detection
  15. GRB 260421A: AstroSat CZTI detection
  16. GOTO26djh/AT2026jpw: radio detection at 15GHz
  17. GRB 260310A: Late-time Chandra X-ray Detection
  18. GRB 260418A: Insight-HXMT/HE detection
  19. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  20. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  21. GRB 260421C: Fermi GBM Final Real-time Localization
  22. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  23. GRB 260421B: BOOTES-7 early optical afterglow detection
  24. GRB 260421B: LCO optical afterglow confirmation
  25. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  26. GRB 260421B: TRT optical counterpart detection
  27. GRB 260421B: SVOM detection of a long burst
  28. GRB 260421B: Fermi GBM Final Real-time Localization
  29. GRB 260421A: Fermi GBM Final Real-time Localization
  30. EP260416a: Optical follow-up observations with Kinder
  31. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  32. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  33. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  34. GRB 260419B: Fermi GBM Final Real-time Localization
  35. GRB 260419A: Fermi GBM Final Real-time Localization
  36. EP260416a: Ondrejov D50 optical detection
  37. GRB 260418B: Fermi GBM Final Real-time Localization
  38. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  39. GRB 260418A: Fermi GBM Final Real-time Localization
  40. Konus-Wind detection of GRB 260411B
  41. GRB 260417B: Fermi GBM Final Real-time Localization
  42. GRB 260417A: AstroSat CZTI detection
  43. IPN triangulation of GRB 260411B
  44. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  45. EP260417a: TRT optical counterpart detection
  46. EP260417a: Einstein Probe detection of an X-ray transient
  47. EP260417b: Einstein Probe detection of a fast X-ray transient
  48. GRB 260414A: Insight-HXMT/HE detection
  49. EP260416a: WFST optical observations and rebrightening
  50. GRB 260417A: Fermi GBM Final Real-time Localization
  51. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  52. GRB 260415B: Glowbug gamma-ray detection
  53. GRB 260411B: Glowbug gamma-ray detection
  54. GRB 260415A: Insight-HXMT/HE detection
  55. EP260416a: COLIBRÍ optical counterpart candidate
  56. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  57. EP260416a: Einstein Probe detection of an X-ray transient
  58. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  59. GRB 260415B: NuSTAR detection of long prompt emission
  60. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  61. GRB 260415B: Fermi GBM Final Localization
  62. GRB 260415A: Fermi GBM Final Real-time Localization
  63. GRB 260414A: Glowbug gamma-ray detection
  64. GRB 260412A: Insight-HXMT/HE detection
  65. GRB 260414A: Fermi GBM Final Real-time Localization
  66. GRB 260410A: Glowbug gamma-ray detection of a short burst
  67. GRB 260413A: Fermi GBM Final Real-time Localization
  68. GRB 260410B: Insight-HXMT/HE detection
  69. GRB 260410A: Insight-HXMT/HE detection
  70. Konus-Wind detection of GRB 260410A (short/hard)
  71. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  72. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  73. GRB 260411B: Fermi-LAT detection
  74. GRB 260412A: SVOM detection of a long burst
  75. GRB 260412A: Fermi GBM Final Real-time Localization
  76. GRB 260411B: COLIBRÍ optical observations
  77. GRB 260411B: Ondrejov D50 optical afterglow detection
  78. GRB260411B: 3.6m DOT optical observation
  79. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  80. GRB 260411B: SVOM/GRM observation of a long burst
  81. GRB 260409A: Insight-HXMT/HE detection
  82. GRB 260411B: Fermi GBM Detection
  83. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  84. GRB 260411B: Fermi GBM Final Real-time Localization
  85. GRB 260411A: Fermi GBM Final Real-time Localization
  86. EP-WXT01709259790: Optical Upper limits with kinder observations
  87. GRB 260410B: SVOM/GRM detection of a short faint burst
  88. GRB 260410B: Fermi GBM Final Real-time Localization
  89. EP-WXT01709259790: Xinglong optical upper limit
  90. GRB 260410A: Fermi-LAT detection
  91. GRB 260410A: Fermi GBM Final Real-time Localization
  92. EP260321a: Chandra X-ray Non-detection
  93. GRB 260409A: Fermi GBM Final Real-time Localization
  94. GRB 260407A: GECAM-A detection
  95. GRB 260407A: Insight-HXMT/HE detection
  96. EP260409a: SVOM/VT optical upper limits
  97. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  98. EP260409a: Einstein Probe detection of an X-ray transient
  99. EP260321a: VLA radio detection
  100. GRB 260404A: Fermi GBM Final Localization

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