The First Data Release of LAMOST Low Resolution Single Epoch Spectra

TL;DR

This paper presents the first data release of individual low-resolution spectra from LAMOST DR5, including measurements of spectral lines and radial velocities, enabling detailed stellar analysis and variability studies.

Contribution

It provides a comprehensive database of individual spectra with new measurements of spectral line equivalent widths and radial velocities, enhancing the utility of LAMOST DR5 data.

Findings

Radial velocity uncertainty is below 5 km/s for same-day observations with high S/N.

Equivalent widths and radial velocities are available for all objects in DR5.

The database supports studies of stellar properties and variability.

Abstract

LAMOST Data Release 5, covering $\sim$17,000 $deg^2$ from $-10^{\circ}$ to $80^{\circ}$ in declination, contains 9 millions co-added low resolution spectra of celestial objects, each spectrum combined from repeat exposure of two to tens of times during Oct 2011 to Jun 2017. In this paper, We present the spectra of individual exposures for all the objects in LAMOST Data Release 5. For each spectrum, equivalent width of 60 lines from 11 different elements are calculated with a new method combining the actual line core and fitted line wings. For stars earlier than F type, the Balmer lines are fitted with both emission and absorption profiles once two components are detected. Radial velocity of each individual exposure is measured by minimizing ${\chi}^2$ between the spectrum and its best template. Database for equivalent widths of spectral lines and radial velocities of individual spectra are available online. Radial velocity uncertainties with different stellar type and signal-to-noise ratio are quantified by comparing different exposure of the same objects. We notice that the radial velocity uncertainty depends on the time lag between observations. For stars observed in the same day and with signal-to-noise ratio higher than 20, the radial velocity uncertainty is below 5km/s, and increase to 10km/s for stars observed in different nights.