The M dwarf planet search programme at the ESO VLT + UVES ^*,**

A search for terrestrial planets in the habitable zone of M dwarfs

¹ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany e-mail: zechmeister@mpia.de
² McDonald Observatory, University of Texas, Austin, TX78712, USA

Received: 13 May 2009
Accepted: 15 July 2009

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 rmsm/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 Hα line strength. For Barnard's star we found a significant anticorrelation, but most of the sample stars do not show such a correlation.