Robert J. Davis

A Survey of Proper-Motion Stars. XVI. Orbital Solutions for 171 Single-lined Spectroscopic Binaries

We report 25,563 radial velocity measurements for 1359 single-lined stars in the Carney-Latham sample of 1464 stars selected for high proper motion. For 171 of these, we present spectroscopic orbital solutions. We find no obvious difference between the binary characteristics in the halo and the disk populations. The observed frequency is the same, and the period distributions are consistent with the hypothesis that the two sets of binaries were drawn from the same parent population. This suggests that metallicity in general, and radiative opacities in particular, have little influence over the fragmentation process that leads to short-period binaries. All the binaries with periods shorter than 10 days have nearly circular orbits, while the binaries with periods longer than 20 days exhibit a wide range of eccentricities and a median value of 0.37. For the metal-poor high-velocity halo binaries in our sample, the transition from circular to eccentric orbits appears to occur at about 20 days, supporting the conclusion that tidal circularization on the main sequence is important for the oldest binaries in the Galaxy.

A survey of proper-motion stars. VI - Orbits for 40 spectroscopic binaries

Orbital solutions are reported for 40 binaries in the Carney and Latham (1987) survey of proper-motion stars. The earlier orbital solutions for HD 85091, BD + 13 3683 deg, and HD 195987 are confirmed, and that for BD -3 2525 deg is revised. The number of orbital solutions for metal-poor binaries has been increased from five to 19, six of which have double lines. For periods longer than 20 days, the distribution of orbital eccentricity for the metal-poor binaries is similar to that for the metal-rich binaries. For the metal-poor binaries, it is found that all the short-period orbits are circular, with a transition to eccentric orbits at a period somewhere between 13 and 18 days. Presumably, the close binaries with short periods were formed with eccentric orbits which were subsequently circularized by tidal mechanisms. 43 references.

A survey of proper motion stars. XI : Orbits for the second 40 spectroscopic binaries

Orbital solutions and spectroscopic metallicities are reported for a second set of 40 spectroscopic binaries found in an extended version of the Carney and Latham survey of proper-motion stars. To investigate the distribution of orbital eccentricity versus period for a pure sample of halo binaries, we select only those systems more metal poor than [m/H] = -1.6. It is found that the transition between circular and eccentric orbits occurs at a period of about 19 days. This supports the interpretation that tidal circularization has been more important on the main sequence than during the pre-main-sequence stage for our sample of old binaries in the halo

RADIAL-VELOCITY CURVES FOR RR LYRAE STARS IN THE GLOBULAR CLUSTERS M5 AND M92 OBTAINED USING SYNTHETIC SPECTRA CROSS-CORRELATION TEMPLATES

Radial velocity curves are presented for the RR Lyrae stars V1 and V3 in the low metallicity globular cluster M92 (NGC 6341) and V8 and V28 in the intermediate metallicity globular cluster M5 (NGC 5904) based on between 50 and 90 observations per star. The radial velocities were derived by cross correlating spectra obtained with the Multiple Mirror Telescope echelle spectrograph with synthetic templates calculated using Kuruczs model atmospheres (ATLAS8) and synthetic spectrum (SYNTHE) codes. The synthetic templates provide a better match to the observed spectra than the available observed templates, especially for the metal-poor stars, resulting in high precision radial velocities good to a few km s-1 in most cases. We find systemic velocities of -125.4, -122.6, +48.7 and +53.6 km s-1 for M92-V1, M92-V3, M5-V8 and M5-V28 respectively, in good agreement with previous determinations of cluster mean velocities.(c) Astronomical Society of the Pacificc Astronomical Society of the Pacificc Astronomical Society of the Pacifi.

Constant-velocity stars at the north galactic pole suitable for use as secondary velocity standards

ABSTRACT We present mean radial velocities for 143 stars in Selected Area 57 at the north Galactic pole that are suitable for use as secondary velocity standards. The stars were drawn from a magnitude‐limited sample and are mostly fainter than 11th magnitude in V. They span a wide range of effective temperatures and surface gravities and thus provide a suitable source of targets for observed templates. The mean radial velocities are based on at least 10 observations spanning at least 8200 days, and are accurate typically to 0.2 km s−1, with no obvious signs of variable velocity or composite spectra.

Spectroscopic Binaries in the Open Cluster M67

For almost 400 members of M67 we have accumulated about 5,000 precise radial velocities. Already we have orbital solutions for more than 32 spectroscopic binaries in M67. Many of these orbits were derived by combining the Palomar and CfA observations, thus extending the time coverage to more than 20 years. The distribution of eccentricity versus period shows evidence for tidal circularization on the main sequence. The transition from circular orbits is fairly clean. Excluding the blue stragglers, the first eccentric orbit has a period of 11.0 days, while the last circular orbit has a period of 12.4 days. For longer periods the distribution of eccentricity is the same as for field stars. The blue straggler S1284 has an eccentric orbit despite its short period of 4.2 days. In 1971 Roger Griffin and Jim Gunn began monitoring the radial velocities of most of the members brighter than the main-sequence turnoff in the old open cluster M67, primarily using the 200-inch Hale Telescope. In 1982, just as the sequence of observations at Palomar was ending, Dave Latham and Bob Mathieu began monitoring many of the same stars with the 1.5-m Tillinghast Reflector and the Multiple-Mirror Telescope on Mount Hopkins. The Palomar and Mount Hopkins data sets were successfully merged, together with some additional CORAVEL velocities kindly provided by Michel Mayor, to obtain 20 years of time coverage (e.g., see Mathieu et al. 1986). Based on these data, orbital solutions have been published (Mathieu et al. 1990) for 22 spectroscopic binaries. The M67 survey is now being extended to V = 15.5 with the telescopes at Mount Hopkins. Already we have 13 additional orbital solutions, with the promise of many more to come. In Table 1 we list the period and eccentricity for 34 spectroscopic binaries which are members of M67. For the binaries with circular orbits, Mathieu et al. (1990) adopted an eccentricity of 0.0. Here we have allowed the eccentricity to be a free parameter in the orbital solution, so that the estimated error in the eccentricity may be used to judge whether the eccentricity is significantly of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S025292110000628X Downloaded from https://www.cambridge.org/core. IP address: 54.70.40.11, on 09 Jun 2019 at 20:49:39, subject to the Cambridge Core terms

Radial-velocity and light variations of IR Cephei

Radial-velocity observations of the short-period Cepheid, IR Cephei, have been used to derive a complete radial-velocity versus phase curve for the variable, to investigate the presence of a possible binary companion, and to address the question of its membership in the Cepheus OB2 association. The observations are consistent with the absence of a close binary companion and shed doubt on its membership in the association. Photoelectric observations made with the Phoenix 10 Automated Photometric Telescope confirm the single nature of the star