CARMENES input catalogue of M dwarfs

Abstract

Context. CARMENES is a stabilised, high-resolution, double-channel spectrograph at the 3.5 m Calar Alto telescope. It is optimally designed for radial-velocity surveys of M dwarfs with potentially habitable Earth-mass planets. Aims. We prepare a list of the brightest, single M dwarfs in each spectral subtype observable from the northern hemisphere, from which we will select the best planet-hunting targets for CARMENES. Methods. In this first paper on the preparation of our input catalogue, we compiled a large amount of public data and collected lowresolution optical spectroscopy with CAFOS at the 2.2 m Calar Alto telescope for 753 stars. We derived accurate spectral types using a dense grid of standard stars, a double least-squares minimisation technique, and 31 spectral indices previously defined by other authors. Additionally, we quantified surface gravity, metallicity, and chromospheric activity for all the stars in our sample. Results. We calculated spectral types for all 753 stars, of which 305 are new and 448 are revised. We measured pseudo-equivalent widths of Hα for all the stars in our sample, concluded that chromospheric activity does not affect spectral typing from our indices, and tabulated 49 stars that had been reported to be young stars in open clusters, moving groups, and stellar associations. Of the 753 stars, two are new subdwarf candidates, three are T Tauri stars, 25 are giants, 44 are K dwarfs, and 679 are M dwarfs. Many of the 261 investigated dwarfs in the range M4.0-8.0 V are among the brightest stars known in their spectral subtype. Conclusions. This collection of low-resolution spectroscopic data serves as a candidate target list for the CARMENES survey and can be highly valuable for other radial-velocity surveys of M dwarfs and for studies of cool dwarfs in the solar neighbourhood.

2MASS 0213+3648 C: A wide T3 benchmark companion to an an active, old M dwarf binary

“…As the activity lifetime changes with the spectral type, we need to know which component this emission comes from. While we were not able to resolve the Hα emission into two separate components in our CAFE spectrum, we were able to measure its equivalent width as −6.6 Å, broadly in agreement with Riaz et al (2006)'s value of −8.1 Å and the value of −6.2 +0.4 −0.2 Å from Alonso- Floriano et al (2015). This emission could in theory come from either component of the inner binary.…”

Radial velocities of K–M dwarfs and local stellar kinematics

“…(Henry et al 2015). Local samples of M-type stars now deserve the utmost attention in search for extra-solar terrestrial planets orbiting nearby stars (e.g., Zechmeister et al 2009;Bean et al 2010;Bonfils et al 2013;Alonso-Floriano et al 2015). Due to their higher planet/star mass ratios, M dwarfs are the most potential targets for detection of low-mass planets by Doppler spectroscopy.…”

Characterization of close visual binaries from the AstraLux Large M Dwarf Survey

“…Bouy et al 2008;Bonnefoy et al 2009;Konopacky et al 2010;Dupuy et al 2010;Schlieder et al 2014;Zhou et al 2014). In addition, the recent discoveries and dedicated surveys for M dwarf planets require accurate stellar physical properties in order to derive reliable planetary parameters, furthering the interest for characterising M dwarfs (e.g., Johnson et al 2012;Mann et al 2012Mann, Gaidos & Ansdell 2013;Muirhead et al 2012Muirhead et al , 2014Dressing & Charbonneau 2013;Newton et al 2014Newton et al , 2015Gaidos et al 2014;Alonso-Floriano et al 2015;Bowler et al 2015).…”