LAMOST-LRS correction factors

We diagnose the errors of radial velocity (RV), atmospheric parameters ([Fe/H], Teff, logg) and alpha-enhancement ([alpha/M]) for the latest data release version of DR7, including 6079235 effective spectra of 4546803 stars. Based on the duplicate observational sample and comparing the deviation of multiple measurements to their given errors, we find that, in general, the error of [alpha/M] is largely underestimated, and the error of RV is slightly overestimated.

We define a correction factor k to quantify these misestimations and correct the errors to be expressed as proper internal uncertainties. Using this self-calibration technique, we find that the k-factors significantly vary with the stellar spectral types and the spectral signal-to-noise ratio (S/N). Particularly, we reveal a strange but evident trend between k-factors and error themselves for all five stellar parameters.