# Looking for Signs of Unresolved Binarity in the Continuum of LAMOST Stellar Spectra

## TL;DR

This study investigates the binarity rate in stellar spectra from LAMOST and Gaia by comparing observed and synthetic spectra, concluding that spectral line intensity comparison is more effective for detecting unresolved binarity.

## Contribution

It introduces a method comparing observed and synthetic spectra to estimate binarity, highlighting the limitations of continuum comparison for this purpose.

## Key findings

- Continuum comparison alone is insufficient to identify unresolved binaries.
- Spectral line intensity comparison is recommended for better binarity detection.
- No binaries were identified using the continuum deviation method.

## Abstract

We describe an attempt to derive the binarity rate of samples of 166 A-, F-, G-, and K-type stars from LAMOST DR5 and 1000 randomly selected presumably single stars from Gaia DR3 catalogs. To this end, we compared continua of the observed spectra with the continua of synthetic spectra in the 3700 to 9097 Angstrom range. The latter spectra were reduced to the LAMOST set of wavelengths, while the former ones were smoothed. Next, we searched for every observed star the nearest synthetic spectrum using a four-parameter representation - effective temperature, gravity, [Fe/H], and a range of interstellar absorption values. However, rms deviations of observed spectra from synthetic ones appeared to be not sufficient to claim that any of the stars is a binary. We conclude that comparison of the intensity of pairs of spectral lines remains the best way to detect binarity.