# The Homogenous Study of Transiting Systems (HoSTS). II. The influence of the line list on stellar parameters

## TL;DR

This study examines how different line lists and fixing surface gravity affect stellar parameter determination from high-resolution spectra, finding that line selection significantly impacts results and differential line lists are slightly more accurate.

## Contribution

It provides a comparative analysis of differential versus laboratory line lists and evaluates the effect of fixing log g on stellar parameter accuracy.

## Key findings

- Differential line lists yield slightly more accurate stellar parameters.
- Fixing log g does not improve spectroscopic parameter accuracy.
- Line selection significantly influences derived stellar parameters.

## Abstract

The use of high resolution, high signal-to-noise stellar spectra is essential in order to determine the most accurate and precise stellar atmospheric parameters via spectroscopy. This is particularly important for determining the fundamental parameters of exoplanets, which directly depend on the stellar properties. However, different techniques can be implemented when analysing these spectra which will influence the results. These include performing an abundance analysis relative to the solar values in order to negate uncertainties in atomic data, and fixing the surface gravity (log g) to an external value such as those from asteroseismology. The choice of lines used will also influence the results. In this paper, we investigate differential analysis and fixing log g for a set of FGK stars that already have accurate fundamental parameters known from external methods. We find that a differential line list gives slightly more accurate parameters compared to a laboratory line list, however the laboratory line list still gives robust parameters. We also find that fixing the log g does not improve the spectroscopic parameters. We investigate the effects of line selection on the stellar parameters and find that the choice of lines used can have a significant effect on the parameters. In particular, removal of certain low excitation potential lines can change the Teff by up to 50 K. For future HoSTS papers we will use the differential line list with a solar microturbulence value of 1 km/s, and we will not fix the log g to an external value.