Radial velocities of K–M dwarfs and local stellar kinematics

Abstract

Aims. The goal of this paper is to present complete radial-velocity data for the spectroscopically selected McCormick sample of nearby K-M dwarfs and, based on these and supplementary data, to determine the space-velocity distributions of late-type stars in the solar neighborhood. Methods. We analyzed nearly 3300 measurements of radial velocities for 1049 K-M dwarfs, that we obtained during the past decade with a CORAVEL-type instrument, with a primary emphasis on detecting and eliminating from kinematic calculations the spectroscopic binaries and binary candidates. Combining radial-velocity data with Hipparcos/Tycho-2 astrometry we calculated the space-velocity components and parameters of the galactic orbits in a three-component model potential for the stars in the sample, that we use for kinematical analysis and for the identification of possible candidate members of nearby stellar kinematic groups. Results. We present the catalog of our observations of radial velocities for 959 stars which are not suspected of velocity variability, along with the catalog of U, V, W velocities and Galactic orbital parameters for a total of 1088 K-M stars which are used in the present kinematic analysis. Of these, 146 stars were identified as possible candidate members of the known nearby kinematic groups and suspected subgroups. The distributions of space-velocity components, orbital eccentricities, and maximum distances from the Galactic plane are consistent with the presence of young, intermediate-age and old populations of the thin disk and a small fraction (∼3%) of stars with the thick disk kinematics. The kinematic structure gives evidence that the bulk of K-M type stars in the immediate solar vicinity represents a dynamically relaxed stellar population. The star MCC 869 is found to be on a retrograde Galactic orbit (V = −262 km s −1 ) of low inclination (4 • ) and can be a member of stellar stream of some dissolved structure. The Sun's velocity with respect to the Local Standard of Rest, derived from the distributions of space-velocity components, is (U , V , W ) = (9.0 ± 1.4, 13.1 ± 0.6, 7.2 ± 0.8) km s −1 . The radial solar motion derived via the Strömberg's relation, V = 14.2 ± 0.8 km s −1 , agrees within the errors with the value obtained directly from the V distribution of stars on nearly circular orbits.

Mass-loss Rates for O and Early B Stars Powering Bow Shock Nebulae: Evidence for Bistability Behavior

“…Our code for calculating peculiar velocities for bowshock stars uses the position, parallax, and proper motion for each star, removes the peculiar solar motion (U,V,W) ⊙ , computes the expected (U,V,W) * for the star's Galactic position given the adopted rotation curve, and computes the peculiar (U,V,W) * pec velocity of the star, i.e., the star's velocity relative to its local standard of rest. Our code reproduces the velocities of over 1000 K-M dwarf stars (Sperauskas, et al 2016) to within 1.1 km s −1 RMS. Uncertainties are propagated by Monte Carlo techniques.…”

The compact multiple system HIP 41431

“…has been conducting a long-term RV survey of nearby low-mass stars using several spectrometers. Most data are obtained at the 1.65-m telescope at the Moletai observatory in Lithuania (Sperauskas et al 2016). A CORAVEL-type spectrometer was used to measure the RVs with a typical accuracy of the order of km s −1 and a spectral resolution around 20000.…”

The Solar Neighborhood. XLII. Parallax Results from the CTIOPI 0.9 m Program—Identifying New Nearby Subdwarfs Using Tangential Velocities and Locations on the H–R Diagram

“…This star has no metallicity measurement in the literature. Sperauskas et al (2016) reported a radial velocity of −285.9±0.2 km s −1 . Although this star's tangential velocity (11.2 km s −1 ) is less than 200 km s −1 , the Gaia parallax (37.49 ± 0.23 mas) and proper motion, combined with the radial velocity measurement, yield U, V, W=(−114, −262, +12).…”