In Data Release 9 of LAMOST, we present measurements of vsini for a total of 121698 stars measured using the Medium Resolution Spectrograph (MRS) and 80108 stars using the Low Resolution Spectrograph (LRS). These values were obtained through a {chi}^2^ minimization process, comparing LAMOST spectra with corresponding grids of synthetically broadened spectra. Due to the resolution and the spectral range of LAMOST, vsini measurements are limited to stars with an effective temperature (Teff) ranging from 5000 to 8500K for MRS and 7000 to 9000K for LRS. The detectable vsini for MRS is set between 27 and 350km/s, and for LRS between 110 and 350km/s. This limitation is because the convolved reference spectra become less informative beyond 350km/s. The intrinsic precision of vsini, determined from multiepoch observations, is approximately ~4.0km/s for MRS and ~10.0km/s for LRS at a signal-to-noise ratio greater than 50. Our vsini values show consistency with those from APOGEE17, displaying a scatter of 8.79km/s. They are also in agreement with measurements from the Gaia DR3 and Sun+ 2021, J/ApJS/257/22 catalogs. An observed trend in LAMOST MRS data is the decrease in vsini with a drop in Teff, particularly transiting around 7000K for dwarfs and 6500K for giants, primarily observed in stars with near-solar abundances.

Cone search capability for table J/ApJS/271/4/table2 (Parameters of LAMOST LRS & MRS v*sin(i) catalogs)