The M dwarf planet search programme at the ESO VLT + UVES. A search for terrestrial planets in the habitable zone of M dwarfs

TL;DR

This study used high-precision radial velocity measurements over seven years to search for terrestrial planets around 40 M dwarfs, finding no planets but setting limits on detectable planet masses and identifying some stellar companions.

Contribution

First long-term RV survey of M dwarfs with UVES achieving 2-2.5 m/s precision, establishing planet detection limits and analyzing stellar activity correlations.

Findings

No planetary companions detected within the sensitivity limits.

Mass detection limits exclude Jupiter-mass planets up to 1 AU for most stars.

Six M dwarfs host brown dwarf or low-mass stellar companions.

Abstract

We present radial velocity (RV) measurements of our sample of 40 M dwarfs from our planet search programme with VLT+UVES begun in 2000. Although with our RV precision down to 2 - 2.5 m/s and timebase line of up to 7 years, we are capable of finding planets of a few Earth masses in the close-in habitable zones of M dwarfs, there is no detection of a planetary companion. To demonstrate this we present mass detection limits allowing us to exclude Jupiter-mass planets up to 1 AU for most of our sample stars. We identified 6 M dwarfs that host a brown dwarf or low-mass stellar companion. With the exception of these, all other sample stars show low RV variability with an rms < 20 m/s. Some high proper motion stars exhibit a linear RV trend consistent with their secular acceleration. Furthermore, we examine our data sets for a possible correlation between RVs and stellar activity as seen in variations of the Halpha line strength. For Barnard's star we found a significant anticorrelation, but most of the sample stars do not show such a correlation.