The Relative Calibration of Radial Velocity for LAMOST Medium Resolution Stellar Spectra

TL;DR

This paper presents a method to correct wavelength calibration systematics in LAMOST MRS spectra, achieving radial velocity precision below 0.5 km/s for multi-epoch observations and identifying stable star candidates.

Contribution

It introduces a technique to correct systematic biases in radial velocity measurements for LAMOST MRS spectra, improving accuracy in time-domain surveys.

Findings

Systematic bias correction reduces radial velocity errors.

Radial velocity zero-point precision reaches below 0.5 km/s.

Constant star candidates identified as potential standards.

Abstract

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) started median-resolution spectroscopic (MRS, R$\sim$7500) survey since October 2018. The main scientific goals of MRS, including binary stars, pulsators, and other variable stars are launched with a time-domain spectroscopic survey. However, the systematic errors, including the bias induced from wavelength calibration and the systematic difference between different spectrographs have to be carefully considered during radial velocity measurement. In this work, we provide a technique to correct the systematics in the wavelength calibration based on the relative radial velocity measurements from LAMOST MRS spectra. We show that, for the stars with multi-epoch spectra, the systematic bias which is induced from the exposures of different nights can be well corrected for LAMOST MRS in each spectrograph. And the precision of radial velocity zero-point of multi-epoch time-domain observations reaches below 0.5 km/s . As a by-product, we also give the constant star candidates, which can be the secondary radial-velocity standard star candidates of LAMOST MRS time-domain surveys.