Secondaries Of Eclipsing Binaries. IV. The Triple System Lambda-Tauri

NSF AST 81-16409, AST 79-22014Astronom

New Precision Orbits Of Bright Double-Lined Spectroscopic Binaries. VIII. HR 1528, HR 6993, 2 Sagittae, And 18 Vulpeculae

Improved orbital elements for four A-star double-lined spectroscopic binaries have been determined with numerous new radial velocities. Three of the four systems, HR 1528, 2 Sge, and 18 Vul, have moderately short orbital periods of 7.05, 7.39, and 9.31 days, respectively, and also have circular or nearly circular orbits. Only HR 6993 with a period of 14.68 days has a significantly eccentric orbit. The close visual companion of 2 Sge has been detected spectroscopically, and its velocity measured. The orbital dimensions (a(1) sin i and a(2) sin i) and minimum masses (m(1) sin(3) i and m(2) sin(3) i) of the short-period binary components all have accuracies of 0.5% or better. We determine basic properties of the individual stars and compare them with solar-abundance evolutionary tracks to estimate their masses. Half of the eight components may be synchronously or pseudosynchronously rotating.NASANSFTennessee State UniversityState of Tennessee through its Centers of ExcellenceAstronom

New Precision Orbits Of Bright Double-Lined Spectroscopic Binaries. III. HD 82191, Omega Draconis, And 108 Herculis

We have determined improved spectroscopic orbits for three double-lined binaries, HD 82191 (Am), omega Dra (F5 V), and 108 Her (Am), using radial velocities from the 2.1 m telescope at McDonald Observatory, the coude feed telescope at Kitt Peak National Observatory, and 2 m telescope at Fairborn Observatory. The orbital periods range from 5.28 to 9.01 days, and all three systems have circular orbits. The new orbital dimensions (a(1) sin i and a(2) sin i) and minimum masses (m(1) sin(3) i and m(2) sin(3) i) have accuracies of 0.2% or better. Our improved results confirm the large minimum masses of HD 82191 and also agree with the values previously found for. Dra. However, for the components of 108 Her our minimum masses are about 20% larger than the previous best values. We conclude that both components of HD 82191 as well as the primary of 108 Her are Am stars. However, the A9 secondary of 108 Her has normal abundances. We estimate spectral types of F4 dwarf and G0 dwarf for the components of. Dra. The primaries of the three binaries are synchronously rotating as is the secondary of 108 Her. The secondaries of HD 82191 and omega Dra are possibly synchronously rotating.NASA NCC5-511NSF HRD-9706268Astronom

Spectroscopic orbits of potential interferometric binaries

We are obtaining high-resolution, red-wavelength spectra at McDonald and Kitt Peak National Observatory to improve the orbits of known spectroscopic binaries that are potential targets for ground-based optical interferometers. The combination of such observations will produce three-dimensional orbits from which very accurate masses and orbital parallaxes can be obtained for double-lined systems. This spectroscopic program will be expanded and placed on the menu of the 2 meter Automatic Spectroscopic Telescope of Tennessee State University once it commences routine operation. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

New Precision Orbits of Bright Double-Lined Spectroscopic Binaries. II. HR 2962, HD 214686, AND 16 PSC

Radial velocities from the 2.1 m telescope at McDonald Observatory and the coudé feed telescope at Kitt Peak National Observatory are used to determine new spectroscopic orbits for the double-lined spectroscopic binaries HR 2962 (F5V), HD 214686 (F8IV), and 16 Psc (F6Vb vw). The new orbital dimensions (a1sin i and a2sin i) and minimum masses (m1sin3i and m2sin3i) have accuracies of 0.1–1%. In the case of HD 214686, which has components of nearly the same mass (m1/m2 = 1.0080 ± 0.0013), we confirm that the component labeled as the primary in previous spectroscopic studies of this system is the slightly more massive component. We find that in HR 2962 the primary is rotating much more rapidly than the pseudosynchronous rate, while the rotation of the secondary is slightly faster than pseudosynchronous; in HD 214686 the primary is rotating at the pseudosynchronous rate or perhaps slightly less, while the rotation of the secondary is pseudosynchronous; and in 16 Psc both components rotate somewhat more rapidly than the pseudosynchronous rates. The three systems, which are of naked-eye brightness, are good potential targets for resolution by modern optical interferometers and so are promising candidates for full determination of their orbits and associated precise masses and distances

New Precision Orbits of Bright Double-lined Spectroscopic Binaries. X. HD 96511, HR 7578, and KZ Andromedae

From an extensive number of newly acquired radial velocities we determine the orbital elements for three late-type dwarf systems, HD 96511, HR 7578, and KZ And. The orbital periods are 18.89737 ± 0.00002, 46.81610 ± 0.00006, and 3.0329113 ± 0.0000005 days, respectively, and all three systems are eccentric, although KZ And is just barely so. We have detected lines of the secondary of HD 96511 for the first time. The orbital dimensions (a1 sin i and a2 sin i) and minimum masses (m1 sin3 i and m2 sin3 i) of the binary components all have accuracies of 0.2% or better. Extensive photometry of the chromospherically active binary HR 7578 confirms a rather long rotation period of 16.446 ± 0.002 days and that the K3 V components do not eclipse. We have estimated the basic properties of the stars in the three systems and compared those results with evolutionary tracks. The results for KZ And that we computed with the revised Hipparcos parallax of van Leeuwen produce inconsistencies. That parallax appears to be too large, and so, instead, we used the original Hipparcos parallax of the common proper motion primary, which improves the results, although some problems remain

HR 8257: a three-dimensional orbit and basic properties

We have used interferometric and spectroscopic observations of HR 8257 to determine a three-dimensional orbit of the system. The orbit has a period of 12.21345 days and an eccentricity of 0.2895. The masses of the F0 and F2 dwarf components are 1.56 and 1.38 M☉ , respectively, with fractional errors of 1.4%. Our orbital parallax of 13.632 ± 0.095 mas, corresponding to a distance of 73.4 ± 0.6 pc, differs from the Hipparcos result by just 2% and has a significantly smaller uncertainty. From our spectroscopic observations and spectral energy distribution modeling we determine the component effective temperatures and luminosities to be T_eff(A) = 7030 ± 200 K and T_(eff)(B) = 6560 ± 200 K and L_A = 9.4 ± 0.3 L☉ and L_B = 4.7 ± 0.2 L☉ . The primary rotates pseudosynchronously, while the secondary is not far from its pseudosynchronous rotational velocity. Although both early-F stars are slowly rotating, neither component of this close binary is an Am star. A comparison with evolutionary tracks indicates that the stars are slightly metal poor, and although the components have evolved away from the zero-age main sequence, they are both still dwarfs

The Chemical Compositions of Galactic Disk F and G Dwarfs

Photospheric abundances are presented for 27 elements from carbon to europium in 181 F-G dwarfs from a differential LTE analysis of high-resolution and high signal-to-noise spectra. Stellar $T_{\rm eff}$ were adopted from an infrared flux method calibration of Str\"{o}mgren photometry. Stellar log $g$ were calculated from {\it Hipparcos} parallaxes and stellar evolutionary tracks. Stellar space motions ($U, V, W$) and a Galactic potential were used to estimate Galactic orbital parameters. Results of $\alpha$-elements -- O, Mg, Si, Ca, and Ti -- show [$\alpha$/Fe] to increase slightly with decreasing [Fe/H]. Heavy elements with dominant contributions at solar metallicity from the $s$-process show [$s$/Fe] to decrease slightly with decreasing [Fe/H]. Scatter in [X/Fe] at a fixed [Fe/H] is entirely attributable to the small measurement errors, after excluding the few thick disc stars and the $s$-process enriched CH subgiants. Tight limits are set on `cosmic' scatter. By combining our sample with published studies, thick disc stars are identified by their $V_{LSR}$ in the range $- 40$ to -100 km s$^{-1}$. These are very old stars with origins in the inner Galaxy and metallicities [Fe/H] $\leq -0.4$. At the same [Fe/H], the sampled thin disc stars have $V_{LSR} \sim 0$ km s$^{-1}$, and are generally younger with a birthplace at about the Sun's Galactocentric distance. In the range $-$0.35 $\geq$ [Fe/H] $\geq$ $-$0.70, well represented by present thin and thick disc samples, [X/Fe] of the thick disc stars is greater than that of thin disc stars for Mg, Al, Si, Ca, Ti, and Eu. [X/Fe] is very similar for the thin and thick disc for -- notably -- Na, and iron-group elements.Comment: 51 pages (includes 19 figures and 6 tables). To appear in MNRAS (paper has been replaced: typos added, In Table~1, [Fe/H]phot has been replaced by spectroscopic [Fe/H] that are used in the plots) (Table1, photometric[Fe/H] values are replaced by spectroscopically derived [Fe/H] that are used in the plots