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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"

28079 results found.

  1. EP260430a: Einstein Probe detection of an X-ray transient
  2. EP260429a: EP-WXT detection of a fast X-ray transient
  3. GRB 260429A: Fermi GBM Final Real-time Localization
  4. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  5. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  6. GRB 260428A: AstroSat CZTI detection
  7. GRB 260424B: Glowbug gamma-ray detection of a short burst
  8. Konus-Wind detection of GRB 260424B
  9. GRB 260428A: Fermi GBM Final Real-time Localization
  10. GRB 260424C: Fermi GBM Final Localization
  11. IPN triangulation of GRB 260424B (short)
  12. GRB 260424B: SVOM/GRM detection of a short burst
  13. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  14. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  15. GRB 260401A: cubesat Avion detection
  16. GRB 260424A: AstroSat CZTI detection of a long burst
  17. GRB 260421B: Kilonova-Catcher optical afterglow detection
  18. GRB 260421B: Insight-HXMT/HE detection
  19. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  20. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  21. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  22. GRB 260419A: AstroSat CZTI detection
  23. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  24. GOTO26djh/AT2026jpw: ATCA radio detection
  25. GRB 260421B: LCO optical counterpart detection
  26. GRB 260421A: AstroSat CZTI detection
  27. GOTO26djh/AT2026jpw: radio detection at 15GHz
  28. GRB 260310A: Late-time Chandra X-ray Detection
  29. GRB 260418A: Insight-HXMT/HE detection
  30. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  31. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  32. GRB 260421C: Fermi GBM Final Real-time Localization
  33. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  34. GRB 260421B: BOOTES-7 early optical afterglow detection
  35. GRB 260421B: LCO optical afterglow confirmation
  36. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  37. GRB 260421B: TRT optical counterpart detection
  38. GRB 260421B: SVOM detection of a long burst
  39. GRB 260421B: Fermi GBM Final Real-time Localization
  40. GRB 260421A: Fermi GBM Final Real-time Localization
  41. EP260416a: Optical follow-up observations with Kinder
  42. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  43. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  44. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  45. GRB 260419B: Fermi GBM Final Real-time Localization
  46. GRB 260419A: Fermi GBM Final Real-time Localization
  47. EP260416a: Ondrejov D50 optical detection
  48. GRB 260418B: Fermi GBM Final Real-time Localization
  49. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  50. GRB 260418A: Fermi GBM Final Real-time Localization
  51. Konus-Wind detection of GRB 260411B
  52. GRB 260417B: Fermi GBM Final Real-time Localization
  53. GRB 260417A: AstroSat CZTI detection
  54. IPN triangulation of GRB 260411B
  55. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  56. EP260417a: TRT optical counterpart detection
  57. EP260417a: Einstein Probe detection of an X-ray transient
  58. EP260417b: Einstein Probe detection of a fast X-ray transient
  59. GRB 260414A: Insight-HXMT/HE detection
  60. EP260416a: WFST optical observations and rebrightening
  61. GRB 260417A: Fermi GBM Final Real-time Localization
  62. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  63. GRB 260415B: Glowbug gamma-ray detection
  64. GRB 260411B: Glowbug gamma-ray detection
  65. GRB 260415A: Insight-HXMT/HE detection
  66. EP260416a: COLIBRÍ optical counterpart candidate
  67. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  68. EP260416a: Einstein Probe detection of an X-ray transient
  69. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  70. GRB 260415B: NuSTAR detection of long prompt emission
  71. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  72. GRB 260415B: Fermi GBM Final Localization
  73. GRB 260415A: Fermi GBM Final Real-time Localization
  74. GRB 260414A: Glowbug gamma-ray detection
  75. GRB 260412A: Insight-HXMT/HE detection
  76. GRB 260414A: Fermi GBM Final Real-time Localization
  77. GRB 260410A: Glowbug gamma-ray detection of a short burst
  78. GRB 260413A: Fermi GBM Final Real-time Localization
  79. GRB 260410B: Insight-HXMT/HE detection
  80. GRB 260410A: Insight-HXMT/HE detection
  81. Konus-Wind detection of GRB 260410A (short/hard)
  82. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  83. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  84. GRB 260411B: Fermi-LAT detection
  85. GRB 260412A: SVOM detection of a long burst
  86. GRB 260412A: Fermi GBM Final Real-time Localization
  87. GRB 260411B: COLIBRÍ optical observations
  88. GRB 260411B: Ondrejov D50 optical afterglow detection
  89. GRB260411B: 3.6m DOT optical observation
  90. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  91. GRB 260411B: SVOM/GRM observation of a long burst
  92. GRB 260409A: Insight-HXMT/HE detection
  93. GRB 260411B: Fermi GBM Detection
  94. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  95. GRB 260411B: Fermi GBM Final Real-time Localization
  96. GRB 260411A: Fermi GBM Final Real-time Localization
  97. EP-WXT01709259790: Optical Upper limits with kinder observations
  98. GRB 260410B: SVOM/GRM detection of a short faint burst
  99. GRB 260410B: Fermi GBM Final Real-time Localization
  100. EP-WXT01709259790: Xinglong optical upper limit

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