Spectral Identification of the u-band Variable Sources in Two LAMOST fields

TL;DR

This study identifies and classifies u-band variable sources in two LAMOST fields, revealing their spectral types, redshifts, and color properties, and distinguishing quasars from stars based on photometric variability and color.

Contribution

It introduces a spectral identification method for u-band variable sources using combined photometric and spectroscopic data, providing a detailed classification of quasars and variable stars.

Findings

11 quasars with redshifts 0.4-1.8 identified

60 variable stars including RR Lyrae and M-dwarfs

Quasars distinguished by u-g color and variability

Abstract

We selected 82 u-band variable objects based on the u-band photometry data from SCUSS and SDSS, in the field of LAMOST Complete Spectroscopic Survey of Pointing Area at Southern Galactic Cap. The magnitude variation of the targets is restricted to larger than 0.2 mag and limiting magnitude down to 19.0 mag in u-band. According to the spectra from LAMOST, there are 11 quasars with red-shift between 0.4 and 1.8, 60 variable stars and 11 unidentified targets. The variable stars include one active M-dwarf with a series of Balmer emission lines, seven Horizontal Branch stars containing six RR Lyrae stars matching with SIMBAD, and one giant, one AGB star and two RR Lyrae candidates by different colour selections. All these variable stars mainly locate near the main sequence in the g-r verse u-g diagram. The quasars are well distinguished from stars by both u-g colour and variation in u-band.