M dwarfs make up 70% of all stars in the Galaxy and are today attractive targets in the search for Earth-sized planets and planets within the habitable zone. However, there are few M dwarfs that are well characterized and the determined stellar parameters have a direct influence on the derived planet properties.
Stellar parameters of M dwarfs are difficult to determine with good accuracy. Their low surface temperature results in an optical spectrum dominated by molecular lines, and previous works have mostly relied on empirical calibrations. In our work we instead use the fact that high-resolution spectrographs operating in the infrared have opened up a new window, at wavelength regions that are less affected by molecular lines. We have shown that we can determine the metallicity and effective temperature using synthetic spectral fitting, resulting in more reliable atmospheric parameters.
We are using our sample of around 30 M dwarfs as a basis for a refined photometric metallicity calibration. A photometric calibration gives us the possibility to explore trends in the metallicity between systems with giant planets, multiple planets or no planets for all discovered exoplanets around M dwarfs. This will give key insights on the formation mechanism of planets around M dwarfs as compared to solar-type stars that have more massive proto-planetary disks.