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We derive a self-consistent set of atmospheric parameters and abundances of 17 elements for the red giant star Arcturus: Teff = 4286 ± 30 K, log g = 1.66 ± 0.05, and [Fe/H] = -0.52 ± 0.04. The effective temperature was determined using model atmosphere fits to the observed spectral energy distribution from the blue to the mid-infrared (0.44 to 10 µm). The surface gravity was calculated using the trigonometric parallax of the star and stellar evolution models. A differential abundance analysis relative to the solar spectrum allowed us to derive iron abundances from equivalent width measurements of 37 FeI and 9 FII lines, unblended in the spectra of both Arcturus and the Sun; the [Fe/H] value adopted is derived from FeI lines. We also determine the mass, radius, and age of Arcturus: M = 1.08 ± 0.06 M⊙, R = 25.4 ± 0.2 R⊙, and Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed Gyr. Finally, abundances of the following elements are measured from an equivalent width analysis of atomic features: C, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, and Zn. We find the chemical composition of Arcturus typical of that of a local thick-disk star, consistent with its kinematics. [ABSTRACT FROM AUTHOR]

The atmospheric parameters of the components of the 16 Cygni binary system, in which the secondary has a gas giant planet detected, are measured accurately using high-quality observational data. Abundances relative to solar are obtained for 25 elements with a mean error of σ([X/H]) = 0.023 dex. The fact that 16 Cyg A has about four times more lithium than 16 Cyg B is normal considering the slightly different masses of the stars. The abundance patterns of 16 Cyg A and B, relative to iron, are typical of that observed in most of the so-called solar twin stars, with the exception of the heavy elements (Z > 30), which can, however, be explained by Galactic chemical evolution. Differential (A-B) abundances are measured with even higher precision (cr(A[X/H]) = 0.018 dex, on average). We find that 16 Cyg A is more metal-rich than 16 Cyg B by Δ[M/H] = +0.041 ± 0.007 dex. On an element-to-element basis, no correlation between the A-B abundance differences and dust condensation temperature (TC) is detected. Based on these results, we conclude that if the process of planet formation around 16 Cyg B is responsible for the observed abundance pattern, the formation of gas giants produces a constant downward shift in the photospheric abundance of metals, without a TC correlation. The latter would be produced by the for≈ῑmation of terrestrial planets instead, as suggested by other recent works on precise elemental abundances. Nevertheless, a scenario consistent with these observations requires the convective envelopes of ≃1 Mʘ stars to reach their present-day sizes about three times quicker than predicted by standard stellar evolution models. [ABSTRACT FROM AUTHOR]

Dynamical information along with survey data on metallicity and in some cases age have been used recently by some authors to search for candidates of stars that were born in the cluster where the Sun formed. We have acquired high-resolution, high signal-to-noise ratio spectra for 30 of these objects to determine, using detailed elemental abundance analysis, if they could be true solar siblings. Only two of the candidates are found to have solar chemical composition. Updated modeling of the stars' past orbits in a realistic Galactic potential reveals that one of them, HD 162826, satisfies both chemical and dynamical conditions for being a sibling of the Sun. Measurements of rare-element abundances for this star further confirm its solar composition, with the only possible exception of Sm. Analysis of long-term high-precision radial velocity data rules out the presence of hot Jupiters and confirms that this star is not in a binary system. We find that chemical tagging does not necessarily benefit from studying as many elements as possible but instead from identifying and carefully measuring the abundances of those elements that show large star-to-star scatter at a given metallicity. Future searches employing data products from ongoing massive astrometric and spectroscopic surveys can be optimized by acknowledging this fact. [ABSTRACT FROM AUTHOR]

Solar infrared colors provide powerful constraints on the stellar effective temperature scale, but they must be measured with both accuracy and precision in order to do so. We fulfill this requirement by using line-depth ratios to derive in a model-independent way the infrared colors of the Sun, and we use the latter to test the zero point of the Casagrande et al. effective temperature scale, confirming its accuracy. Solar colors in the widely used Two Micron All Sky Survey (2MASS) JHKs and WISEW1-4 systems are provided: (V – J)☼ = 1.198, (V – H)☼ = 1.484, (V – Ks)☼ = 1.560, (J – H)☼ = 0.286, (J – Ks)☼ = 0.362, (H – Ks)☼ = 0.076, (V – W1)☼ = 1.608, (V – W2)☼ = 1.563, (V – W3)☼ = 1.552, and (V – W4)☼ = 1.604. A cross-check of the effective temperatures derived implementing 2MASS or WISE magnitudes in the infrared flux method confirms that the absolute calibration of the two systems agrees within the errors, possibly suggesting a 1% offset between the two, thus validating extant near- and mid-infrared absolute calibrations. While 2MASS magnitudes are usually well suited to derive , we find that a number of bright, solar-like stars exhibit anomalous WISE colors. In most cases, this effect is spurious and can be attributed to lower-quality measurements, although for a couple of objects (3% ± 2% of the total sample) it might be real, and may hint at the presence of warm/hot debris disks. [ABSTRACT FROM AUTHOR]

Oxygen abundances of 67 dwarf stars in the metallicity range –1.6 < [Fe/H] < –0.4 are derived from a non-LTE analysis of the 777 nm O I triplet lines. These stars have precise atmospheric parameters measured by Nissen and Schuster, who find that they separate into three groups based on their kinematics and α-element (Mg, Si, Ca, Ti) abundances: thick disk, high-α halo, and low-α halo. We find the oxygen abundance trends of thick-disk and high-α halo stars very similar. The low-α stars show a larger star-to-star scatter in [O/Fe] at a given [Fe/H] and have systematically lower oxygen abundances compared to the other two groups. Thus, we find the behavior of oxygen abundances in these groups of stars similar to that of the α elements. We use previously published oxygen abundance data of disk and very metal-poor halo stars to present an overall view (–2.3 < [Fe/H] < +0.3) of oxygen abundance trends of stars in the solar neighborhood. Two field halo dwarf stars stand out in their O and Na abundances. Both G53-41 and G150-40 have very low oxygen and very high sodium abundances, which are key signatures of the abundance anomalies observed in globular cluster (GC) stars. Therefore, they are likely field halo stars born in GCs. If true, we estimate that at least 3% ± 2% of the local field metal-poor star population was born in GCs. [ABSTRACT FROM AUTHOR]

We derive atmospheric parameters and lithium abundances for 671 stars and include our measurements in a literature compilation of 1381 dwarf and subgiant stars. First, a “lithium desert” in the effective temperature (Teff) versus lithium abundance (ALi) plane is observed such that no stars with Teff ≃ 6075 K and ALi ≃ 1.8 are found. We speculate that most of the stars on the low ALi side of the desert have experienced a short-lived period of severe surface lithium destruction as main-sequence or subgiant stars. Next, we search for differences in the lithium content of thin-disk and thick-disk stars, but we find that internal processes have erased from the stellar photospheres their possibly different histories of lithium enrichment. Nevertheless, we note that the maximum lithium abundance of thick-disk stars is nearly constant from [Fe/H] = –1.0 to –0.1, at a value that is similar to that measured in very metal-poor halo stars (ALi ≃ 2.2). Finally, differences in the lithium abundance distribution of known planet-host stars relative to otherwise ordinary stars appear when restricting the samples to narrow ranges of Teff or mass, but they are fully explained by age and metallicity biases. We confirm the lack of a connection between low lithium abundance and planets. However, we find that no low ALi planet-hosts are found in the desert Teff window. Provided that subtle sample biases are not responsible for this observation, this suggests that the presence of gas giant planets inhibit the mechanism responsible for the lithium desert. [ABSTRACT FROM AUTHOR]

Photometric data in the UBV(RI)C system have been acquired for 80 solar analog stars for which we have previously derived highly precise atmospheric parameters Teff, log g, and [Fe/H] using high-resolution, high signal-to-noise ratio spectra. UBV and (RI)C data for 46 and 76 of these stars, respectively, are published for the first time. Combining our data with those from the literature, colors in the UBV(RI)C system, with ≃ 0.01 mag precision, are now available for 112 solar analogs. Multiple linear regression is used to derive the solar colors from these photometric data and the spectroscopically derived Teff, log g, and [Fe/H] values. To minimize the impact of systematic errors in the model-dependent atmospheric parameters, we use only the data for the 10 stars that most closely resemble our Sun, i.e., the solar twins, and derive the following solar colors: (B – V)☼ = 0.653 ± 0.005, (U – B)☼ = 0.166 ± 0.022, (V – R)☼ = 0.352 ± 0.007, and (V – I)☼ = 0.702 ± 0.010. These colors are consistent, within the 1σ errors, with those derived using the entire sample of 112 solar analogs. We also derive the solar colors using the relation between spectral-line-depth ratios and observed stellar colors, i.e., with a completely model-independent approach, and without restricting the analysis to solar twins. We find (B – V)☼ = 0.653 ± 0.003, (U – B)☼ = 0.158 ± 0.009, (V – R)☼ = 0.356 ± 0.003, and (V – I)☼ = 0.701 ± 0.003, in excellent agreement with the model-dependent analysis. [ABSTRACT FROM AUTHOR]